Phosphatidylinositol 3-kinase-dependent activation of trypsinogen modulates the severity of acute pancreatitis

Melatonin ameliorates multiorgan injuries induced by severe acute pancreatitis in mice by regulating the Nrf2 signaling pathway

Severe acute pancreatitis (SAP) is a complicated inflammatory reaction that impacts the pancreas, often resulting in damage to numerous organs. This disorder encompasses a range of processes such as inflammation, oxidative stress, and pancreatitis. The hormone melatonin (MT) is primarily secreted by the pineal gland and plays a crucial role in mitigating inflammation, countering the harmful effects of free radicals, and regulating oxidative stress. The aim of this research was to investigate the potential protective impact and the underlying mechanism of melatonin in mice afflicted with SAP. The biochemical and histological assessments unequivocally demonstrated that melatonin effectively inhibited necrosis, infiltration, edema and cell death in pancreatic tissues, thereby suppressing acute pancreatitis. Notably, melatonin also alleviated the consequent harm to distant organs, notably the lungs, liver, and kidneys. Furthermore, both preventive and therapeutic administration of melatonin prompted nuclear factor E2-related factor 2 (Nrf2) activation followed by Nrf2 target gene expression. Nrf2 initiates the activation of antioxidant genes, thereby providing defense against oxidative stress. Conversely, Nrf2 reduction may contribute to impaired antioxidant protection in SAP. The beneficial impact of Nrf2 on antioxidants was absent in Nrf2-knockout mice, leading to the accumulation of LDH and exacerbation of cell death. This deterioration in both pancreatitis and injuries in distant organs intensified significantly. The results indicate that melatonin has an enhanced ability to protect against multiorgan damage caused by SAP, which is accomplished through the increase in Nrf2 expression. Additionally, Nrf2 initiates the activation of antioxidant genes that offer defense against cell death.

Urolithin A attenuates severity of chronic pancreatitis associated with continued alcohol intake by inhibiting PI3K/AKT/mTOR signaling

Heavy alcohol consumption is the dominant risk factor for chronic pancreatitis (CP); however, treatment and prevention strategies for alcoholic chronic pancreatitis (ACP) remains limited. The present study demonstrates that ACP induction in C57BL/6 mice causes significant acinar cell injury, pancreatic stellate cell (PSC) activation, exocrine function insufficiency, and an increased fibroinflammatory response when compared with alcohol or CP alone. Although the withdrawal of alcohol during ACP recovery led to reversion of pancreatic damage, continued alcohol consumption with established ACP perpetuated pancreatic injury. In addition, phosphokinase array and Western blot analysis of ACP-induced mice pancreata revealed activation of the phosphatidylinositol 3 kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) and cyclic AMP response element binding protein (CREB) signaling pathways possibly orchestrating the fibroinflammatory program of ACP pathogenesis. Mice treated with urolithin A (Uro A, a gut-derived microbial metabolite) in the setting of ACP with continued alcohol intake (during the recovery period) showed suppression of AKT and P70S6K activation, and acinar damage was significantly reduced with a parallel reduction in pancreas-infiltrating macrophages and proinflammatory cytokine accumulation. These results collectively provide mechanistic insight into the impact of Uro A on attenuation of ACP severity through suppression of PI3K/AKT/mTOR signaling pathways and can be a useful therapeutic approach in patients with ACP with continuous alcohol intake.NEW & NOTEWORTHY Our novel findings presented here demonstrate the utility of Uro A as an effective therapeutic agent in attenuating alcoholic chronic pancreatitis (ACP) severity with alcohol continuation after established disease, through suppression of the PI3K/AKT/mTOR signaling pathway.

Transcriptomics and Network Pharmacology Reveal the Protective Effect of Chaiqin Chengqi Decoction on Obesity-Related Alcohol-Induced Acute Pancreatitis via Oxidative Stress and PI3K/Akt Signaling Pathway

Obesity-related acute pancreatitis (AP) is characterized by increasing prevalence worldwide and worse clinical outcomes compared to AP of other etiologies. Chaiqin chengqi decoction (CQCQD), a Chinese herbal formula, has long been used for the clinical management of AP but its therapeutic actions and the underlying mechanisms have not been fully elucidated. This study has investigated the pharmacological mechanisms of CQCQD in a novel mouse model of obesity-related alcohol-induced AP (OA-AP). The mouse OA-AP model was induced by a high-fat diet for 12 weeks and subsequently two intraperitoneal injections of ethanol, CQCQD was administered 2 h after the first injection of ethanol. The severity of OA-AP was assessed and correlated with changes in transcriptomic profiles and network pharmacology in the pancreatic and adipose tissues, and further docking analysis modeled the interactions between compounds of CQCQD and their key targets. The results showed that CQCQD significantly reduced pancreatic necrosis, alleviated systemic inflammation, and decreased the parameters associated with multi-organ dysfunction. Transcriptomics and network pharmacology analysis, as well as further experimental validation, have shown that CQCQD induced Nrf2/HO-1 antioxidant protein response and decreased Akt phosphorylation in the pancreatic and adipose tissues. In vitro, CQCQD protected freshly isolated pancreatic acinar cells from H₂O₂-elicited oxidative stress and necrotic cell death. The docking results of AKT1 and the active compounds related to AKT1 in CQCQD showed high binding affinity. In conclusion, CQCQD ameliorates the severity of OA-AP by activating of the antioxidant protein response and down-regulating of the PI3K/Akt signaling pathway in the pancreas and visceral adipose tissue.

Proteomic analysis of early phosphorylated proteins in acute pancreatitis model

Background and Objective:

The exact mechanism of acute pancreatitis (AP), which is an inflammation of the pancreas, still remains unclear. In this study, we examined the protein phosphorylation changes during the early stage of AP in mice using proteomic analysis.

Methods:

AP model in mice was constructed using an intraperitoneal injection of cerulein. Blood samples and pancreas were collected at 1, 3, 6, 9h after the final injection (n=3 at each time point). Samples collected 3h after the final injection were separately mixed and named S (saline group) and C1 (cerulein group); samples collected 6h after the final injection from the cerulein group were mixed and named C2. Proteins from S, C1, and C2 were extracted, digested by trypsin, and subjected to LC-MS/MS analysis, bioinformatics analysis, and Western blotting.

Results:

A total of 549 sites (426 proteins) were upregulated, and 501 sites (367 proteins) were downregulated in C1 compared to S; while 491 phosphorylation sites (377 proteins) were upregulated and 367 sites (274 proteins) were downregulated in C2 compared to S. Motif analysis showed that proline-directed kinase and basophilic kinase had a key role during early AP. During an early AP stage, the cellular distributions of proteins slightly changed. The types of domains changed with the development of AP. Phosphorylation proteins associated with calcium signaling, especially IP3R mediated calcium release, lysosome and autophagosome pathway, pancreatic digestive activation, and secretion, were found to be involved in the development of early AP independent of NF-kB activation. Moreover, the MAPK family was found to have a greater impact at the early stage of AP. We also found differentially expressed phosphorylations of amylase and trypsinogen and increased phosphorylation of MAPK6 S189 in early AP.

Conclusion:

IP3R mediated calcium release and activation of MAPK family are key events promoting the development of early AP.

Abdominal paracentesis drainage attenuates severe acute pancreatitis by enhancing cell apoptosis via PI3K/AKT signaling pathway

Our previous studies have shown that abdominal paracentesis drainage (APD) is a safe and effective strategy for patients with severe acute pancreatitis (SAP). However, the underlying mechanisms behind APD treatment remain poorly understood. Given that apoptosis is a critical pathological response of SAP, we here aim to investigate the effect of APD on cell apoptosis in pancreatic tissues during SAP and to explore its potential molecular mechanism. SAP was induced by 5% sodium-taurocholate retrograde while APD group was inserted a drainage tube into the right lower abdomen of rats immediately after SAP induction. Histopathological staining, serum amylase, endotoxin and inflammatory mediators were measured. Cell apoptosis, apoptosis-related proteins and signaling pathway were also evaluated. Our results demonstrated that APD treatment significantly attenuated pancreatic damage and decreased the serum levels of amylase, endotoxin, TNF-α, IL-1 and IL-6 in rats with SAP. Notably, APD treatment enhanced cell apoptosis and reduced necrosis in pancreatic tissues, as evidenced by Tunnel staining, the increased pro-apoptosis proteins (Cleaved-caspase-3 and bax) and decreased anti-apoptosis protein (Bcl-2). Moreover, the effect of APD on cell apoptosis was further confirmed by the regulatory pathway of PI3K/AKT and NF-kB signaling pathway. These results suggest that APD attenuates the severity of SAP by enhancing cell apoptosis via suppressing PI3K/AKT signaling pathway. Our findings provide new insights for understanding the effectiveness of APD in patients with SAP.

A critical role for Akt1 signaling in acute pancreatitis progression†

Acute pancreatitis (AP) is an inflammatory disease of the pancreas that causes significant morbidity and mortality worldwide. Unfortunately, there is no specific treatment available to date. Several studies have previously shown that inhibitors of the PI3K/Akt axis downregulate the degree of inflammation in animal models of AP. However, studies on in vivo side-effects of such inhibitors are still lacking. In a recent issue of The Journal of Pathology, Chen, Malagola et al investigated if inhibition of Akt signaling plays a negative role in the regenerative phase of AP. They showed that treating AP mice with an Akt inhibitor (MK2206) impaired acinar regeneration and increased the development of acinar-to-ductal metaplasia. This is the first study to highlight the negative impact of an Akt inhibitor on cellular regeneration while simultaneously inhibiting inflammation in AP. The authors also suggested combining Akt activators to recover pancreatic regeneration. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Material basis and molecular mechanisms of Dachengqi decoction in the treatment of acute pancreatitis based on network pharmacology

BACKGROUND

Dachengqi decoction (DCQD) is a classical prescription in traditional Chinese medicine (TCM). It has been used to treat abdominal pain and acute pancreatitis (AP) for thousands of years in China.

OBJECTIVE

To predict the active components and signaling pathway of DCQD and to further explore the potential molecular mechanism of DCQD as a treatment of AP using network pharmacology.

METHODS

Network pharmacology and bioinformatics were used to determine the active components of DCQD and its potential target in the treatment of AP. The AP model was induced by Cerulein (Cer) combined with lipopolysaccharide (LPS). The pharmacodynamic basis of DCQD in the treatment of AP was evaluated in vitro and in vivo and Western blot analysis and immunofluorescence were used to determine the molecular mechanism of DCQD.

RESULTS

Screening using relevant databases and topological analysis revealed 71 active components and 535 potential target proteins in DCQD. In addition, 445 differential genes for AP were also screened. Pathway enrichment analysis, PPI network analysis and transcription factor prediction showed that DCQD played an important role in the PI3K-Akt signal pathway, and 17 DCQD monomers were found in this signal pathway. In the AP model, DCQD promoted pancreatic acinar cell apoptosis, reduction in inflammation, and regulation of the PI3K-AKT signaling pathway. DCQD inhibited the expression of p-AKT and p- NF-kB proteins in pancreatic tissue of the AP model both in vitro and in vivo.

CONCLUSION

This study reveals that 17 active components of DCQD improve AP by regulating the PI3K/AKT signaling pathway and promoting apoptosis and suppressing pathological injury and inflammation.

Elevated intracellular trypsin exacerbates acute pancreatitis and chronic pancreatitis in mice

Intra-acinar trypsinogen activation occurs in the earliest stages of pancreatitis and is believed to play important roles in pancreatitis pathogenesis. However, the exact role of intra-acinar trypsin activity in pancreatitis remains elusive. Here, we aimed to examine the specific effects of intra-acinar trypsin activity on the development of pancreatitis using a transgenic mouse model. This transgenic mouse model allowed for the conditional expression of a mutant trypsinogen that can be activated specifically inside pancreatic acinar cells. We found that expression of this active mutated trypsin had no significant effect on triggering spontaneous pancreatitis. Instead, several protective compensatory mechanisms, including SPINK1 and heat shock proteins, were upregulated. Notably, these transgenic mice developed much more severe acute pancreatitis, compared with control mice, when challenged with caerulein. Elevated tissue edema, serum amylase, inflammatory cell infiltration and acinar cell apoptosis were dramatically associated with increased trypsin activity. Furthermore, chronic pathological changes were observed in the pancreas of all transgenic mice, including inflammatory cell infiltration, parenchymal atrophy and cell loss, fibrosis, and fatty replacement. These changes were not observed in control mice treated with caerulein. The alterations in pancreata from transgenic mice mimicked the histological changes common to human chronic pancreatitis. Taken together, we provided in vivo evidence that increased intra-acinar activation of trypsinogen plays an important role in the initiation and progression of both acute and chronic pancreatitis. NEW & NOTEWORTHY Trypsinogen is activated early in pancreatitis. However, the roles of trypsin in the development of pancreatitis have not been fully addressed. Using a genetic approach, we showed trypsin activity is critical for the severity of both acute and chronic pancreatitis.

Dihydrodiosgenin protects against experimental acute pancreatitis and associated lung injury through mitochondrial protection and PI3Kγ/Akt inhibition

BACKGROUND AND PURPOSE

Acute pancreatitis (AP) is a painful and distressing disorder of the exocrine pancreas with no specific treatment. Diosgenyl saponins extracted from from Dioscorea zingiberensis C. H. Wright have been reported to protect against experimental models of AP. Diosgenin, or its derivatives are anti-inflammatory in various conditions. However, the effects of diosgenin and its spiroacetal ring opened analogue, dihydrodiosgenin (Dydio), on AP have not been determined.

EXPERIMENTAL APPROACH

Effects of diosgenin and Dydio on sodium taurocholate hydrate (Tauro)-induced necrosis were tested, using freshly isolated murine pancreatic acinar cells. Effects of Dydio on mitochondrial dysfunction in response to Tauro, cholecystokinin-8 and palmitoleic acid ethyl ester were also assessed. Dydio (5 or 10 mg·kg^-1 ) was administered after the induction in vivo of Tauro-induced AP (Wistar rats), caerulein-induced AP and palmitoleic acid plus ethanol-induced AP (Balb/c mice). Pancreatitis was assessed biochemically and histologically. Activation of pancreatic PI3Kγ/Akt was measured by immunoblotting.

KEY RESULTS

Dydio inhibited Tauro-induced activation of the necrotic cell death pathway and prevented pancreatitis stimuli-induced mitochondrial dysfunction. Therapeutic administration of Dydio ameliorated biochemical and histopathological responses in all three models of AP through pancreatic mitochondrial protection and PI3Kγ/Akt inactivation. Moreover, Dydio improved pancreatitis-associated acute lung injury through preventing excessive inflammatory responses.

CONCLUSION AND IMPLICATIONS

These data provide in vitro and in vivo mechanistic evidence that the diosgenin analogue, Dydio could be potential treatment for AP. Further medicinal optimization of diosgenin and its analogue might be a useful strategy for identifying lead candidates for inflammatory diseases.

Pathogenic mechanisms of pancreatitis

Pancreatitis is inflammation of pancreas and caused by a number of factors including pancreatic duct obstruction, alcoholism, and mutation in the cationic trypsinogen gene. Pancreatitis is represented as acute pancreatitis with acute inflammatory responses and; chronic pancreatitis characterized by marked stroma formation with a high number of infiltrating granulocytes (such as neutrophils, eosinophils), monocytes, macrophages and pancreatic stellate cells (PSCs). These inflammatory cells are known to play a central role in initiating and promoting inflammation including pancreatic fibrosis, i.e., a major risk factor for pancreatic cancer. A number of inflammatory cytokines are known to involve in promoting pancreatic pathogenesis that lead pancreatic fibrosis. Pancreatic fibrosis is a dynamic phenomenon that requires an intricate network of several autocrine and paracrine signaling pathways. In this review, we have provided the details of various cytokines and molecular mechanistic pathways (i.e., Transforming growth factor-β/SMAD, mitogen-activated protein kinases, Rho kinase, Janus kinase/signal transducers and activators, and phosphatidylinositol 3 kinase) that have a critical role in the activation of PSCs to promote chronic pancreatitis and trigger the phenomenon of pancreatic fibrogenesis. In this review of literature, we discuss the involvement of several pro-inflammatory and anti-inflammatory cytokines, such as in interleukin (IL)-1, IL-1β, IL-6, IL-8 IL-10, IL-18, IL-33 and tumor necrosis factor-α, in the pathogenesis of disease. Our review also highlights the significance of several experimental animal models that have an important role in dissecting the mechanistic pathways operating in the development of chronic pancreatitis, including pancreatic fibrosis. Additionally, we provided several intermediary molecules that are involved in major signaling pathways that might provide target molecules for future therapeutic treatment strategies for pancreatic pathogenesis.

Sulforaphane Protects Pancreatic Acinar Cell Injury by Modulating Nrf2-Mediated Oxidative Stress and NLRP3 Inflammatory Pathway

Acute pancreatitis (AP) is characterized by early activation of intra-acinar proteases followed by acinar cell death and inflammation. Cellular oxidative stress is a key mechanism underlying these pathological events. Sulforaphane (SFN) is a natural organosulfur antioxidant with undescribed effects on AP. Here we investigated modulatory effects of SFN on cellular oxidation and inflammation in AP. AP was induced by cerulean hyperstimulation in BALB/c mice. Treatment group received a single dose of 5 mg/kg SFN for 3 consecutive days before AP. We found that SFN administration attenuated pancreatic injury as evidenced by serum amylase, pancreatic edema, and myeloperoxidase, as well as by histological examination. SFN administration reverted AP-associated dysregulation of oxidative stress markers including pancreatic malondialdehyde and redox enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx). In acinar cells, SFN treatment upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) expression and Nrf2-regulated redox genes including quinoneoxidoreductase-1, heme oxidase-1, SOD1, and GPx1. In addition, SFN selectively suppressed cerulein-induced activation of the nucleotide-binding domain leucine-rich repeat containing family, pyrin domain-containing 3 (NLRP3) inflammasome, in parallel with reduced nuclear factor- (NF-) κB activation and modulated NF-κB-responsive cytokine expression. Together, our data suggested that SFN modulates Nrf2-mediated oxidative stress and NLRP3/NF-κB inflammatory pathways in acinar cells, thereby protecting against AP.

Release of Cathepsin B in Cytosol Causes Cell Death in Acute Pancreatitis

BACKGROUND & AIMS

Experimental studies in acute pancreatitis (AP) suggest a strong association of acinar cell injury with cathepsin B-dependent intracellular activation of trypsin. However, the molecular events subsequent to trypsin activation and their role, if any, in cell death is not clear. In this study, we have explored intra-acinar events downstream of trypsin activation that lead to acinar cell death.

METHODS

Acinar cells prepared from the pancreas of rats or mice (wild-type, trypsinogen 7, or cathepsin B-deleted) were stimulated with supramaximal cerulein, and the cytosolic activity of cathepsin B and trypsin was evaluated. Permeabilized acini were used to understand the differential role of cytosolic trypsin vs cytosolic cathepsin B in activation of apoptosis. Cell death was evaluated by measuring specific markers for apoptosis and necrosis.

RESULTS

Both in vitro and in vivo studies have suggested that during AP cathepsin B leaks into the cytosol from co-localized organelles, through a mechanism dependent on active trypsin. Cytosolic cathepsin B but not trypsin activates the intrinsic pathway of apoptosis through cleavage of bid and activation of bax. Finally, excessive release of cathepsin B into the cytosol can lead to cell death through necrosis.

CONCLUSIONS

This report defines the role of trypsin in AP and shows that cytosolic cathepsin B but not trypsin activates cell death pathways. This report also suggests that trypsin is a requisite for AP only because it causes release of cathepsin B into the cytosol.

Spautin-1 Ameliorates Acute Pancreatitis via Inhibiting Impaired Autophagy and Alleviating Calcium Overload

Acute pancreatitis is characterized by zymogen pre-activation. Severe inflammation caused by zymogen activation can eventually lead to multiple organ dysfunctions, which contributes to the high mortality rate of severe acute pancreatitis. However, there is no specific treatment available for acute pancreatitis therapy. Here, we show that spautin-1, which effectively inhibits autophagy flux, ameliorated the pathogenesis of acute pancreatitis induced by cerulein or L-Arginine. CaMKII phosphorylation due to cytosolic calcium oeverload was revealed in this paper. It was also demonstrated that autophagic protein aggregates degradation blockade accompanying with impaired autophagy correlated positively to intra acinar cells digestive aymogen activation sitimulated by cerulein or L-Arginine. The role of spautin-1 in ameliorating acute pancreatitis was shown here to be associated with impaired autophagy inhibition and Ca²⁺ overload alleviation. We provided a promising therapy for acute pancreatitis here through targeting both impaired autophagy and increased cytosolic calcium.

Role of phosphoinositide-3 kinase signaling pathways in pathogenesis of acute pancreatitis

Acute pancreatitis (AP) as a common acute disease poses a great threat to people's health. According to statistics, about one-fifth of cases develop acute respiratory distress syndrome and multiple organ dysfunction, which result in high mortality. The early understanding of the pathogenesis of this disease is limited to an inflammatory response resulting in autodigestion, edema, hemorrhage and necrosis of pancreatic tissue after the abnormal activation of trypsin. In recent years, researchers have focused their research on the role of immune inflammatory response in the pathogenesis of AP. Here we discuss the relationship between the immune inflammation and PI3K signaling pathways in AP.

Suppression of Phosphatidylinositol 3-Kinase/Akt Signaling Attenuates Hypoxia-Induced Pulmonary Hypertension Through the Downregulation of Lysyl Oxidase

Lysyl oxidase (LOX) is a copper-dependent enzyme that catalyzes covalent cross-linking of collagen. In response to hypoxia, phosphatidylinositol 3-kinase (PI3K) pathway is activated and contributes to pulmonary arterial hypertension (PAH). However, potential role of LOX in hypoxia-induced PAH is poorly understood. In this study, we explored the mechanism responsible for the development of hypoxia-induced PAH. Potent inhibitors of PI3K/Akt and LOX, wortmannin and β-aminopropionitrile (β-APN), were administrated in rat model of hypoxia-induced PAH. The cross-linking of collagen was assessed by the determination of hydroxyproline. LOX, LOXL-1, LOXL-2, LOXL-3, LOXL-4, Akt, and phospho-Akt expression was detected by real-time polymerase chain reaction and western blot analysis. We observed that collagen cross-linking and LOX activity were elevated in hypoxia-exposed rat lung tissue, but these effects were reversed by β-APN and wortmannin. In addition, exposure to hypoxia enhanced mRNA and protein expression and activity of LOX and LOXL-1 in a PI3K/Akt-dependent manner and induced the development of PAH. After the administration of wortmannin, the upregulation of LOX and cross-linking of collagen were significantly reversed in hypoxia-exposed rat pulmonary artery tissue. Taken together, the present study demonstrated that the upregulation of LOX expression and collagen cross-linking is PI3K/Akt dependent in rat with hypoxia-induced PAH. Suppression of PI3K/Akt pathway may alleviate hypoxia-induced PAH through the downregulation of LOX.

Inhibition of pancreatic oxidative damage by stilbene derivative dihydro-resveratrol: implication for treatment of acute pancreatitis

Trans-resveratrol is a natural stilbenoid possessing multifarious pharmacological benefits; however, when orally consumed, it is rapidly metabolised by colonic microflora and converted to dihydro-resveratrol. Thus, this microbial metabolite is of great therapeutic relevance. In the present study, upon the oral administration of dihydro-resveratrol (10–50 mg/kg), the severity of acute pancreatitis in the cerulein-treated rats was significantly ameliorated as evidenced by decreased α-amylase activities in the plasma and lessened oedema formation in the pancreatic parenchyma. In addition, the generation of intracellular reactive oxidative products, including malondialdehyde and protein carbonyls, was accordingly reduced, so as the production of pro-inflammatory cytokines. While inhibiting the activities of NADPH oxidase and myeloperoxidase, the depletion of glutathione was considerably restored. Importantly, the attenuation of pancreatic oxidative damage by dihydro-resveratrol was associated with a down-regulation of the nuclear factor-kappaB and phosphatidylinositol 3′-kinase-serine/threonine kinase signalling pathways. Furthermore, we demonstrated that the solubility of dihydro-resveratrol was at least 5 times higher than trans-resveratrol whilst exhibiting a much lower cytotoxicity. Collectively, the current findings accentuate new mechanistic insight of dihydro-resveratrol in pancreatic oxidative damage, and advocate its therapeutic potential for the management of acute pancreatitis, particularly for patients unresponsive to trans-resveratrol due to the lack of proper microbial strains.

Peripancreatic fat necrosis worsens acute pancreatitis independent of pancreatic necrosis via unsaturated fatty acids increased in human pancreatic necrosis collections

BACKGROUND AND AIMS

Peripancreatic fat necrosis occurs frequently in necrotising pancreatitis. Distinguishing markers from mediators of severe acute pancreatitis (SAP) is important since targeting mediators may improve outcomes. We evaluated potential agents in human pancreatic necrotic collections (NCs), pseudocysts (PCs) and pancreatic cystic neoplasms and used pancreatic acini, peripheral blood mononuclear cells (PBMC) and an acute pancreatitis (AP) model to determine SAP mediators.

METHODS

We measured acinar and PBMC injury induced by agents increased in NCs and PCs. Outcomes of caerulein pancreatitis were studied in lean rats coadministered interleukin (IL)-1β and keratinocyte chemoattractant/growth-regulated oncogene, triolein alone or with the lipase inhibitor orlistat.

RESULTS

NCs had higher fatty acids, IL-8 and IL-1β versus other fluids. Lipolysis of unsaturated triglyceride and resulting unsaturated fatty acids (UFA) oleic and linoleic acids induced necro-apoptosis at less than half the concentration in NCs but other agents did not do so at more than two times these concentrations. Cytokine coadministration resulted in higher pancreatic and lung inflammation than caerulein alone, but only triolein coadministration caused peripancreatic fat stranding, higher cytokines, UFAs, multisystem organ failure (MSOF) and mortality in 97% animals, which were prevented by orlistat.

CONCLUSIONS

UFAs, IL-1β and IL-8 are elevated in NCs. However, UFAs generated via peripancreatic fat lipolysis causes worse inflammation and MSOF, converting mild AP to SAP.

Expression of phosphatidylinositol-3 kinase and effects of inhibitor Wortmannin on expression of tumor necrosis factor-α in severe acute pancreatitis associated with acute lung injury

BACKGROUND

Acute lung injury (ALI) is a common and serious complication of severe acute pancreatitis (SAP). The study aimed to investigate the protective effect and mechanism of phosphatidylinositol-3 kinase (PI3K) inhibitor Wortmannin in SAP associated with ALI.

METHODS

Ninety rats were randomly divided into three groups: sham operation (SO) group (n=30), SAP group (n=30), and SAP+Wortmannin (SAP+W) group (n=30). SAP model was induced by retrograde injection of 4% sodium taurocholate into the biliopancreatic duct of rats. The rate of lung water content, myeloperoxidase (MPO), matrix metalloproteinase 9 (MMP-9), protein kinase B (PKB), abdphosphorylation of protein kinase B (P-PKB) activity in the lung tissue were evaluated.

RESULTS

In the SAP group, the p-PKB expression in the lung tissue began to rise at 3 hours after modeling, and peaked at 12 hours (P<0.05); the rate of lung water content, MPO and TNF-α activity were also gradually increased, and the degree of lung lesion gradually increased (P<0.05). In the SAP+Wortmannin group, the p-PKB expression in the lung tissue began to rise at 3 hours after modeling, and peaked at 12 hours; it was higher than that in the SO group (P<0.05), but significantly lower than that in the SAP group (P<0.05). The rest indicators in the SAP+Wortmannin group were also significantly decreased as compared with the SAP group (P<0.05).

CONCLUSIONS

The expression of phosphatidylinositol-3 kinase/protein kinase B was elevated in severe pancreatitis rats with lung injury. This suggested that PI3K signal transduction pathway is involved in the control and release of proinflammatory cytokines TNF-α, which may play an important role in the pathogenesis of severe acute pancreatitis associated with lung injury. This finding indicated that Wortmannin can block the PI3K signal transduction pathway, and inhibit the release of inflammatory factor TNF-α.

Wortmannin, PI3K/Akt signaling pathway inhibitor, attenuates thyroid injury associated with severe acute pancreatitis in rats

Increasing evidences suggest that PI3K/AKT pathway plays an important role in the pathogenesis of inflammatory diseases such as acute pancreatitis. However, the exact effect of PI3K/AKT on thyroid injury associated with acute pancreatitis has not been investigated. This study aimed to investigate the protective effects of wortmannin, PI3K/AKT inhibitor, on thyroid injury in a rat model of severe acute pancreatitis (SAP). Sixty male SD rats were randomly divided into four groups: sham operating group (SO), SAP group, wortmannin treatment (WOR) group and drug control (WOR-CON) group. Serum amylase (AMY), lipase (LIP) and thyroid hormone levels were evaluated. The morphological change of thyroid tissue was analyzed under the light and transmission electron microscopy. AKT, P38MAPK and NF-κB expression in the thyroid tissue was evaluated by immunohistochemical staining. Oxidative stress and inflammatory cytokines were detected. Results showed that wortmannin attenuated the following: (1) serum AMY, LIP and thyroid hormone (2) pancreatic and thyroid pathological injuries (3) thyroid MDA, (4) thyroid ultrastructural change, (5) serum TNF-α, IL-6 and IL-1β (6) AKT, MAPKP38 and NF-κB expression in thyroid tissues. These results suggested that wortmannin attenuates thyroid injury in SAP rats, presumably because of its role on prevent ROS generation and inhibits the activation of P38MAPK, NF-κB pathway. Our findings provide new therapeutic targets for thyroid injury associated with SAP.

Abnormal mechanosensing and cofilin activation promote the progression of ascending aortic aneurysms in mice

Smooth muscle cells (SMCs) and the extracellular matrix (ECM) are intimately associated in the aortic wall. Fbln4(SMKO) mice with an SMC-specific deletion of the Fbln4 gene, which encodes the vascular ECM component fibulin-4, develop ascending aortic aneurysms that have increased abundance of angiotensin-converting enzyme (ACE); inhibiting angiotensin II signaling within the first month of life prevents aneurysm development. We used comparative proteomics analysis of Fbln4(SMKO) aortas from postnatal day (P) 1 to P30 mice to identify key molecules involved in aneurysm initiation and expansion. At P14, the actin depolymerizing factor cofilin was dephosphorylated and thus activated, and at P7, the abundance of slingshot-1 (SSH1) phosphatase, an activator of cofilin, was increased, leading to actin cytoskeletal remodeling. Also, by P7, biomechanical changes and underdeveloped elastic lamina-SMC connections were evident, and the abundance of early growth response 1 (Egr1), a mechanosensitive transcription factor that stimulates ACE expression, was increased, which was before the increases in ACE abundance and cofilin activation. Postnatal deletion of Fbln4 in SMCs at P7 prevented cofilin activation and aneurysm formation, suggesting that these processes required disruption of elastic lamina-SMC connections. Phosphoinositide 3-kinase (PI3K) is involved in the angiotensin II-mediated activation of SSH1, and administration of PI3K inhibitors from P7 to P30 decreased SSH1 abundance and prevented aneurysms. These results suggest that aneurysm formation arises from abnormal mechanosensing of SMCs resulting from the loss of elastic lamina-SMC connections and from increased SSH1 and cofilin activity, which may be potential therapeutic targets for treating ascending aortic aneurysms.

Early to Late Endosome Trafficking Controls Secretion and Zymogen Activation in Rodent and Human Pancreatic Acinar Cells

BACKGROUND & AIMS

Pancreatic acinar cells have an expanded apical endosomal system, the physiological and pathophysiological significance of which is still emerging. Phosphatidylinositol-3,5-bisphosphate (PI(3,5)P₂) is an essential phospholipid generated by PIKfyve, which phosphorylates phosphatidylinositol-3-phosphate (PI(3)P). PI(3,5)P₂ is necessary for maturation of early endosomes (EE) to late endosomes (LE). Inhibition of EE to LE trafficking enhances anterograde endosomal trafficking and secretion at the plasma membrane by default through a recycling endosome (RE) intermediate. We assessed the effects of modulating PIKfyve activity on apical trafficking and pancreatitis responses in pancreatic acinar cells.

METHODS

Inhibition of EE to LE trafficking was achieved using pharmacological inhibitors of PIKfyve, expression of dominant negative PIKfyve K1877E, or constitutively active Rab5-GTP Q79L. Anterograde endosomal trafficking was manipulated by expression of constitutively active and dominant negative Rab11a mutants. The effects of these agents on secretion, endolysosomal exocytosis of lysosome associated membrane protein (LAMP1), and trypsinogen activation in response to high-dose CCK-8, bile acids and cigarette toxin was determined.

RESULTS

PIKfyve inhibition increased basal and stimulated secretion. Adenoviral overexpression of PIKfyve decreased secretion leading to cellular death. Expression of Rab5-GTP Q79L or Rab11a-GTP Q70L enhanced secretion. Conversely, dominant-negative Rab11a-GDP S25N reduced secretion. High-dose CCK inhibited endolysosomal exocytosis that was reversed by PIKfyve inhibition. PIKfyve inhibition blocked intracellular trypsin accumulation and cellular damage responses to high CCK-8, tobacco toxin, and bile salts in both rodent and human acini.

CONCLUSIONS

These data demonstrate that EE-LE trafficking acutely controls acinar secretion and the intracellular activation of zymogens leading to the pathogenicity of acute pancreatitis.

High-mobility group box 1 protein and its role in severe acute pancreatitis

The high mobility group box 1 (HMGB1), which belongs to the subfamily of HMG-1/-2, is a highly conserved single peptide chain consisting of 215 amino acid residues with a molecular weight of approximately 24894 Da. HMGB1 is a ubiquitous nuclear protein in mammals and plays a vital role in inflammatory diseases. Acute pancreatitis is one of the most common causes of acute abdominal pain with a poor prognosis. Acute pancreatitis is an acute inflammatory process of the pancreas (duration of less than six months), for which the severe form is called severe acute pancreatitis (SAP). More and more studies have shown that HMGB1 has a bidirectional effect in the pathogenesis of SAP. Extracellular HMGB1 can aggravate the pancreatic inflammatory process, whereas intracellular HMGB1 has a protective effect against pancreatitis. The mechanism of HMGB1 is multiple, mainly through the nuclear factor-κB pathway. Receptors for advanced glycation end-products and toll-like receptors (TLR), especially TLR-2 and TLR-4, are two major types of receptors mediating the inflammatory process triggered by HMGB1 and may be also the main mediators in the pathogenesis of SAP. HMGB1 inhibitors, such as ethyl pyruvate, pyrrolidine dithiocarbamate and Scolopendra subspinipes mutilans, can decrease the level of extracellular HMGB1 and are the promising targets in the treatment of SAP.

Transforming growth factor (TGF)-β-induced microRNA-216a promotes acute pancreatitis via Akt and TGF-β pathway in mice

BACKGROUND

Both transforming growth factor β (TGF-β) and MicroRNA-216a (miR-216a) were reported to be upregulated during acute pancreatitis (AP). Moreover, miR-216a can be induced by TGF-β.

AIM

This study aimed to investigate how TGF-β and miR-216a involved in the pathogenesis of AP both in a mouse model and in rat pancreatic acinar AR42J cells.

METHODS

Cerulein-induced AP mouse model was established and pretreated with a TGF-β inhibitor, SB431542. Serum amylase, lipase, tumor necrosis factor (TNF)-α, interleukin 6 (IL-6), TGF-β and histopathological changes of pancreas were determined. Expression of miR-216a was detected by quantitative real-time RT-PCR. Bioinformatics was utilized to predict the targets of miR-216a. Expression levels of phosphatase and tensin homolog (PTEN), mothers against decapentaplegic homolog 7 (Smad7), TGF-β receptor I, total Akt and pAkt were detected by Western blot.

RESULTS

SB431542 significantly decreased serum amylase, lipase, TNF-α, IL-6, TGF-β, histopathological changes of pancreas and expression of miR-216a in cerulein-induced mouse (P < 0.05). TGF-β induced miR-216a in AR42J cells. PTEN and Smad7 were identified to be the possible targets of miR-216a. Transfection of miR-216a mimics (or inhibitors) in AR42J cells downregulated (or upregulated) the expression of PTEN and Smad7, thus affected the expression of downstream pAkt and TGF-β receptor I. The expression changes of these protein caused by miR-216a can be regulated by SB431542 both in mouse model and AR42J cells.

CONCLUSIONS

TGF-β promotes AP by inducing miR-216a targeting PTEN and Smad7, thus through PI3K/Akt and TGF-β feedback pathway.

Acute lipotoxicity regulates severity of biliary acute pancreatitis without affecting its initiation

Obese patients have worse outcomes during acute pancreatitis (AP). Previous animal models of AP have found worse outcomes in obese rodents who may have a baseline proinflammatory state. Our aim was to study the role of acute lipolytic generation of fatty acids on local severity and systemic complications of AP. Human postpancreatitis necrotic collections were analyzed for unsaturated fatty acids (UFAs) and saturated fatty acids. A model of biliary AP was designed to replicate the human variables by intraductal injection of the triglyceride glyceryl trilinoleate alone or with the chemically distinct lipase inhibitors orlistat or cetilistat. Parameters of AP etiology and outcomes of local and systemic severity were measured. Patients with postpancreatitis necrotic collections were obese, and 13 of 15 had biliary AP. Postpancreatitis necrotic collections were enriched in UFAs. Intraductal glyceryl trilinoleate with or without the lipase inhibitors resulted in oil red O-positive areas, resembling intrapancreatic fat. Both lipase inhibitors reduced the glyceryl trilinoleate-induced increase in serum lipase, UFAs, pancreatic necrosis, serum inflammatory markers, systemic injury, and mortality but not serum alanine aminotransferase, bilirubin, or amylase. We conclude that UFAs are enriched in human necrotic collections and acute UFA generation via lipolysis worsens pancreatic necrosis, systemic inflammation, and injury associated with severe AP. Inhibition of lipolysis reduces UFA generation and improves these outcomes of AP without interfering with its induction.

Role of phosphoinositide 3-kinase in the pathogenesis of acute pancreatitis

A large body of experimental and clinical data supports the notion that inflammation in acute pancreatitis has a crucial role in the pathogenesis of local and systemic damage and is a major determinant of clinical severity. Thus, research has recently focused on molecules that can regulate the inflammatory processes, such as phosphoinositide 3-kinases (PI3Ks), a family of lipid and protein kinases involved in intracellular signal transduction. Studies using genetic ablation or pharmacologic inhibitors of different PI3K isoforms, in particular the class I PI3Kδ and PI3Kγ, have contributed to a greater understanding of the roles of these kinases in the modulation of inflammatory and immune responses. Recent data suggest that PI3Ks are also involved in the pathogenesis of acute pancreatitis. Activation of the PI3K signaling pathway, and in particular of the class IB PI3Kγ isoform, has a significant role in those events which are necessary for the initiation of acute pancreatic injury, namely calcium signaling alteration, trypsinogen activation, and nuclear factor-κB transcription. Moreover, PI3Kγ is instrumental in modulating acinar cell apoptosis, and regulating local neutrophil infiltration and systemic inflammatory responses during the course of experimental acute pancreatitis. The availability of PI3K inhibitors selective for specific isoforms may provide new valuable therapeutic strategies to improve the clinical course of this disease. This article presents a brief summary of PI3K structure and function, and highlights recent advances that implicate PI3Ks in the pathogenesis of acute pancreatitis.

Interleukin-1β induces autophagy by affecting calcium homeostasis and trypsinogen activation in pancreatic acinar cells

The strong up-regulation of inflammatory mediators has been reported to play a key role in acute pancreatitis (AP). Elevated serum levels of interleukin-1β (IL-1β) are associated with the development of AP. However, the precise effect and mechanism of IL-1β in AP remains obscure. In this study, we investigated the potential role and mechanism of IL-1β in AP. We measured autophagy activation in response to IL-1β in AR42J cells. The disrupting effects of IL-1β on cellular Ca(2+) were observed. To determine whether the disruption of Ca(2+) signaling has protective effects in vivo during AP, male C57BL/6 mice were treated with cerulein to induce AP. We found that the treatment of AR42J cells with IL-1β triggered autophagy and that the autophagic flux was impaired. In addition, IL-1β induced Ca(2+) release from the ER. Furthermore, the expression of the ER stress markers GRP78 and IRE1 also increased. 2APB, an antagonist of the InsP3 receptor, inhibited increased expression of autophagy markers. Subsequent biochemical assays revealed that co-culture with IL-1β could induce the activation of trypsinogen to trypsin and reduce the viability of acinar cells. Pathological changes of the pancreas were also observed in vivo. We found that the pathological injuries of the pancreas were significantly alleviated in mice co-treated with 2APB. Taken together, our results indicate that IL-1β can induce trypsin activation and decrease cellular viability in pancreatic acinar cells. These effects depend on impaired autophagy via intracellular calcium changes. Ca(2+) signaling may become a promising therapeutic target in the treatment of pancreatitis.

Role of pancreatic fat in the outcomes of pancreatitis

The role of obesity in relation to various disease processes is being increasingly studied, with reports over the last several years increasingly mentioning its association with worse outcomes in acute disease. Obesity has also gained recognition as a risk factor for severe acute pancreatitis (SAP).The mortality in SAP may be as high as 30% and is usually attributable to multi system organ failure (MSOF) earlier in the disease, and complications of necrotizing pancreatitis later [9-11]. To date there is no specific treatment for acute pancreatitis (AP) and the management is largely expectant and supportive. Obesity in general has also been associated with poor outcomes in sepsis and other pathological states including trauma and burns. With the role of unsaturated fatty acids (UFA) as propagators in SAP having recently come to light and with the recognition of acute lipotoxicity, there is now an opportunity to explore different strategies to reduce the mortality and morbidity in SAP and potentially other disease states associated with such a pathophysiology. In this review we will discuss the role of fat and implications of the consequent acute lipotoxicity on the outcomes of acute pancreatitis in lean and obese states and during acute on chronic pancreatitis.

Regulatory roles of the PI3K/Akt signaling pathway in rats with severe acute pancreatitis

The phosphatidylinositol 3-kinase(PI3K)/protein kinase B (Akt) pathway plays a key role in inflammation. However, the regulatory roles of PI3K/Akt in severe acute pancreatitis (SAP) have not been elucidated. The aim of this study was to investigate the impact of wortmannin, a PI3K/Akt inhibitor, on SAP rats through exposure to sodium taurocholate (STC) after 3 h and 6 h. The SAP group was found to have a significant increase in pancreas Akt expression, along with the activation of serum amylase, TNF-α, IL-1β, and IL-6, and pancreas histological aggravation. The administration of wortmannin in SAP rats reduced Akt expression, attenuated the level of serum amylase and inflammation factor, and alleviated the damage of pancreatic tissue. Furthermore, the administration of wortmannin led to an obvious reduction in NF-κB and p38MAPK expression in SAP rats. These findings showed that the PI3K/Akt inhibitor wortmannin decreases inflammatory cytokines in SAP rats and suggests its regulatory mechanisms may occur through the suppression on NF-κB and p38MAPK activity.

Src Dependent Pancreatic Acinar Injury Can Be Initiated Independent of an Increase in Cytosolic Calcium

Several deleterious intra-acinar phenomena are simultaneously triggered on initiating acute pancreatitis. These culminate in acinar injury or inflammatory mediator generation in vitro and parenchymal damage in vivo. Supraphysiologic caerulein is one such initiator which simultaneously activates numerous signaling pathways including non-receptor tyrosine kinases such as of the Src family. It also causes a sustained increase in cytosolic calcium- a player thought to be crucial in regulating deleterious phenomena. We have shown Src to be involved in caerulein induced actin remodeling, and caerulein induced changes in the Golgi and post-Golgi trafficking to be involved in trypsinogen activation, which initiates acinar cell injury. However, it remains unclear whether an increase in cytosolic calcium is necessary to initiate acinar injury or if injury can be initiated at basal cytosolic calcium levels by an alternate pathway. To study the interplay between tyrosine kinase signaling and calcium, we treated mouse pancreatic acinar cells with the tyrosine phosphatase inhibitor pervanadate. We studied the effect of the clinically used Src inhibitor Dasatinib (BMS-354825) on pervanadate or caerulein induced changes in Src activation, trypsinogen activation, cell injury, upstream cytosolic calcium, actin and Golgi morphology. Pervanadate, like supraphysiologic caerulein, induced Src activation, redistribution of the F-actin from its normal location in the sub-apical area to the basolateral areas, and caused antegrade fragmentation of the Golgi. These changes, like those induced by supraphysiologic caerulein, were associated with trypsinogen activation and acinar injury, all of which were prevented by Dasatinib. Interestingly, however, pervanadate did not cause an increase in cytosolic calcium, and the caerulein induced increase in cytosolic calcium was not affected by Dasatinib. These findings suggest that intra-acinar deleterious phenomena may be initiated independent of an increase in cytosolic calcium. Other players resulting in acinar injury along with the Src family of tyrosine kinases remain to be explored.

The clinical course of acute pancreatitis and the inflammatory mediators that drive it

Acute pancreatitis (AP) is a common emergency condition. In the majority of cases, it presents in a mild and self-limited form. However, about 20% of patients develop severe disease with local pancreatic complications (including necrosis, abscess, or pseudocysts), systemic organ dysfunction, or both. A modern classification of AP severity has recently been proposed based on the factors that are causally associated with severity of AP. These factors are both local (peripancreatic necrosis) and systemic (organ failure). In AP, inflammation is initiated by intracellular activation of pancreatic proenzymes and/or nuclear factor-κB. Activated leukocytes infiltrate into and around the pancreas and play a central role in determining AP severity. Inflammatory reaction is first local, but may amplify leading to systemic overwhelming production of inflammatory mediators and early organ failure. Concomitantly, anti-inflammatory cytokines and specific cytokine inhibitors are produced. This anti-inflammatory reaction may overcompensate and inhibit the immune response, rendering the host at risk for systemic infection. Currently, there is no specific treatment for AP. However, there are several early supportive treatments and interventions which are beneficial. Also, increasing the understanding of the pathogenesis of systemic inflammation and the development of organ dysfunction may provide us with future treatment modalities.

Protein kinases - new targets for treatment of acute pancreatitis

Acute pancreatitis (AP) is a common acute abdomen. Although most cases of AP are self-limited, severe AP is still associated with a higher mortality rate. Protein kinases are involved in almost all intracellular signal transduction pathways, and AP-related protein kinases may be good targets for treatment of AP. Numerous studies have investigated the protein kinases and their specific inhibitors involved in AP in recent years. Here we utilized the data mining method to summarize protein kinases and kinase inhibitors that correlate with AP and highlight several important protein kinases, with an aim to provide new clues to the treatment of AP.

The role of calcium in acute pancreatitis

Until recently, it was unclear whether calcium is more than a bystander in the development of acute pancreatitis. Now important evidence has been accumulated supporting a pivotal role of intracellular levels of calcium in the early pathogenesis of the disease. A sustained increase of cytosolic calcium concentrations, as observed in various models of acute pancreatitis, was identified as sabotaging crucial cellular defense mechanisms and initiating premature trypsinogen activation. These processes lead the acinar cell to necrosis, with spillage of activated proteases into the interstitial space, affecting surrounding acinar cells and initiating a vicious circle that ends in macroscopic acute pancreatitis and systemic inflammatory response syndrome. Comprehensive knowledge of the pathobiology of cytosolic calcium in the pancreatic acinar cell is leading to the understanding of coherent molecular pathways of early events in the pathogenesis of acute pancreatitis and is opening horizons for research into directly targeted therapeutic agents.

Pathogenic mechanisms of acute pancreatitis

PURPOSE OF REVIEW

In this article, recent advances in the pathogenesis of acute pancreatitis have been reviewed.

RECENT FINDINGS

Pathologic intra-acinar trypsinogen activation had been hypothesized to be the central mechanism of pancreatitis for over a century. This hypothesis could be explored for the first time with the development of a novel mouse model lacking pathologic intra-acinar trypsinogen activation. It became clear that intra-acinar trypsinogen activation contributes to early acinar injury, but local and systemic inflammation progress independently during pancreatitis. Early intra-acinar nuclear factor kappa B (NFκB) activation, which occurs parallel to but independent of trypsinogen activation, may be crucial in pancreatitis. Although the mechanism of NFκB and trypsinogen activation is not entirely clear, further insights have been made into key pathogenic cellular events such as calcium signaling, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, autophagy and impaired trafficking, and lysosomal and secretory responses. Cellular intrinsic damage-sensing mechanisms that lead to activation of the inflammatory response aimed at repair, but lead to disease when overwhelmed, are beginning to be understood.

SUMMARY

New findings necessitate a paradigm shift in our understanding of acute pancreatitis. Intra-acinar trypsinogen activation leads to early pancreatic injury, but the inflammatory response of acute pancreatitis develops independently, driven by early activation of inflammatory pathways.

Lipotoxicity causes multisystem organ failure and exacerbates acute pancreatitis in obesity

Obesity increases the risk of adverse outcomes during acute critical illnesses such as burns, severe trauma, and acute pancreatitis. Although individuals with more body fat and higher serum cytokines and lipase are more likely to experience problems, the roles that these characteristics play are not clear. We used severe acute pancreatitis as a representative disease to investigate the effects of obesity on local organ function and systemic processes. In obese humans, we found that an increase in the volume of intrapancreatic adipocytes was associated with more extensive pancreatic necrosis during acute pancreatitis and that acute pancreatitis was associated with multisystem organ failure in obese individuals. In vitro studies of pancreatic acinar cells showed that unsaturated fatty acids were proinflammatory, releasing intracellular calcium, inhibiting mitochondrial complexes I and V, and causing necrosis. Saturated fatty acids had no such effects. Inhibition of lipolysis in obese (ob/ob) mice with induced pancreatitis prevented a rise in serum unsaturated fatty acids and prevented renal injury, lung injury, systemic inflammation, hypocalcemia, reduced pancreatic necrosis, and mortality. Thus, therapeutic approaches that target unsaturated fatty acid-mediated lipotoxicity may reduce adverse outcomes in obese patients with critical illnesses such as severe acute pancreatitis.

ADP-ribosylation factor 1 protein regulates trypsinogen activation via organellar trafficking of procathepsin B protein and autophagic maturation in acute pancreatitis

Several studies have suggested that autophagy might play a deleterious role in acute pancreatitis via intra-acinar activation of digestive enzymes. The prototype for this phenomenon is cathepsin B-mediated trypsin generation. To determine the organellar basis of this process, we investigated the subcellular distribution of the cathepsin B precursor, procathepsin B. We found that procathepsin B is enriched in Golgi-containing microsomes, suggesting a role for the ADP-ribosylation (ARF)-dependent trafficking of cathepsin B. Indeed, caerulein treatment increased processing of procathepsin B, whereas a known ARF inhibitor brefeldin A (BFA) prevented this. Similar treatment did not affect processing of procathepsin L. BFA-mediated ARF1 inhibition resulted in reduced cathepsin B activity and consequently reduced trypsinogen activation. However, formation of light chain 3 (LC3-II) was not affected, suggesting that BFA did not prevent autophagy induction. Instead, sucrose density gradient centrifugation and electron microscopy showed that BFA arrested caerulein-induced autophagosomal maturation. Therefore, ARF1-dependent trafficking of procathepsin B and the maturation of autophagosomes results in cathepsin B-mediated trypsinogen activation induced by caerulein.

Pancreatic secretory trypsin inhibitor I reduces the severity of chronic pancreatitis in mice overexpressing interleukin-1β in the pancreas

IL-1β is believed to play a pathogenic role in the development of pancreatitis. Expression of human IL-1β in pancreatic acinar cells produces chronic pancreatitis, characterized by extensive intrapancreatic inflammation, atrophy, and fibrosis. To determine if activation of trypsinogen is important in the pathogenesis of chronic pancreatitis in this model, we crossed IL-1β transgenic [Tg(IL1β)] mice with mice expressing a trypsin inhibitor that is normally produced in rat pancreatic acinar cells [pancreatic secretory trypsin inhibitor (PTSI) I]. We previously demonstrated that transgenic expression of PSTI-I [Tg(Psti1)] increased pancreatic trypsin inhibitor activity by 190%. Tg(IL1β) mice were found to have marked pancreatic inflammation, characterized by histological changes, including acinar cell loss, inflammatory cell infiltration, and fibrosis, as well as elevated myeloperoxidase activity and elevated pancreatic trypsin activity, as early as 6 wk of age. In contrast to Tg(IL1β) mice, pancreatitis was significantly less severe in dual-transgenic [Tg(IL1β)-Tg(Psti1)] mice expressing IL-1β and PSTI-I in pancreatic acinar cells. These findings indicate that overexpression of PSTI-I reduces the severity of pancreatitis and that pancreatic trypsin activity contributes to the pathogenesis of an inflammatory model of chronic pancreatitis.

Intra-acinar trypsinogen activation mediates early stages of pancreatic injury but not inflammation in mice with acute pancreatitis

BACKGROUND & AIMS

The role of trypsinogen activation in the pathogenesis of acute pancreatitis (AP) has not been clearly established.

METHODS

We generated and characterized mice lacking trypsinogen isoform 7 (T7) gene (T(-/-)). The effects of pathologic activation of trypsinogen were studied in these mice during induction of AP with cerulein. Acinar cell death, tissue damage, early intra-acinar activation of the transcription factor nuclear factor κB (NF-κB), and local and systemic inflammation were compared between T(-/-) and wild-type mice with AP.

RESULTS

Deletion of T7 reduced the total trypsinogen content by 60% but did not affect physiologic function. T(-/-) mice lacked pathologic activation of trypsinogen, which occurs within acinar cells during early stages of AP progression. Absence of trypsinogen activation in T(-/-) mice led to near complete inhibition of acinar cell death in vitro and a 50% reduction in acinar necrosis during AP progression. However, T(-/-) mice had similar degrees of local and systemic inflammation during AP progression and comparable levels of intra-acinar NF-κB activation, which was previously shown to occur concurrently with trypsinogen activation during early stages of pancreatitis.

CONCLUSIONS

T7 is activated during pathogenesis of AP in mice. Intra-acinar trypsinogen activation leads to acinar death during early stages of pancreatitis, which accounts for 50% of the pancreatic damage in AP. However, progression of local and systemic inflammation in AP does not require trypsinogen activation. NF-κB is activated early in acinar cells, independently of trypsinogen activation, and might be responsible for progression of AP.

Insulin protects pancreatic acinar cells from cytosolic calcium overload and inhibition of plasma membrane calcium pump

Acute pancreatitis is a serious and sometimes fatal inflammatory disease of the pancreas without any reliable treatment or imminent cure. In recent years, impaired metabolism and cytosolic Ca(2+) ([Ca(2+)](i)) overload in pancreatic acinar cells have been implicated as the cardinal pathological events common to most forms of pancreatitis, regardless of the precise causative factor. Therefore, restoration of metabolism and protection against cytosolic Ca(2+) overload likely represent key therapeutic untapped strategies for the treatment of this disease. The plasma membrane Ca(2+)-ATPase (PMCA) provides a final common path for cells to "defend" [Ca(2+)](i) during cellular injury. In this paper, we use fluorescence imaging to show for the first time that insulin treatment, which is protective in animal models and clinical studies of human pancreatitis, directly protects pancreatic acinar cells from oxidant-induced cytosolic Ca(2+) overload and inhibition of the PMCA. This protection was independent of oxidative stress or mitochondrial membrane potential but appeared to involve the activation of Akt and an acute metabolic switch from mitochondrial to predominantly glycolytic metabolism. This switch to glycolysis appeared to be sufficient to maintain cellular ATP and thus PMCA activity, thereby preventing Ca(2+) overload, even in the face of impaired mitochondrial function.

PI3K/Akt signaling pathway is involved in the pathogenesis of ulcerative colitis

OBJECTIVE

The purpose of this study was to investigate the role of the PI3K/Akt signaling pathway in the pathogenesis of ulcerative colitis (UC).

MATERIALS AND METHODS

Mucosal biopsy specimens from 54 active UC cases and adjacent normal tissues from 18 colon cancer cases were investigated. Twenty-eight Balb/c mice were randomly divided into four groups. Dextran sulphate sodium (DSS) solution (5%) was used to develop the mouse colitis model. After treatment with wortmannin (a PI3K inhibitor), disease activity index (DAI) and histological score was determined for each group of mice. Expression of phosphorylated Akt (p-Akt) in UC patients and mouse intestinal mucosa was determined by immunohistochemical staining. We also determined the effect of wortmannin on tumor necrosis factor-α (TNF-α) expression in intestinal biopsy tissues of UC patients and mice with DSS-induced colitis.

RESULTS

Wortmannin significantly reduced the level of p-Akt and TNF-α in the colitis tissues of UC patients and DSS-treated mice. Wortmannin significantly alleviated the inflammation of colitis as assessed by DAI and histological score in DSS-treated mice.

CONCLUSION

The PI3K/Akt signal transduction pathway is involved in the regulation and release of pro-inflammatory cytokines such as TNF-α and plays an important role in the development and progression of UC.

Neuroprotective multifunctional iron chelators: from redox-sensitive process to novel therapeutic opportunities

Accumulating evidence suggests that many cytotoxic signals occurring in the neurodegenerative brain can initiate neuronal death processes, including oxidative stress, inflammation, and accumulation of iron at the sites of the neuronal deterioration. Neuroprotection by iron chelators has been widely recognized with respect to their ability to prevent hydroxyl radical formation in the Fenton reaction by sequestering redox-active iron. An additional neuroprotective mechanism of iron chelators is associated with their ability to upregulate or stabilize the transcriptional activator, hypoxia-inducible factor-1alpha (HIF-1alpha). HIF-1alpha stability within the cells is under the control of a class of iron-dependent and oxygen-sensor enzymes, HIF prolyl-4-hydroxylases (PHDs) that target HIF-1alpha for degradation. Thus, an emerging novel target for neuroprotection is associated with the HIF system to promote stabilization of HIF-1alpha and increase transcription of HIF-1-related survival genes, which have been reported to be regulated in patient's brains afflicted with diverse neurodegenerative diseases. In accordance, a new potential therapeutic strategy for neurodegenerative diseases is explored, by which iron chelators would inhibit PHDs, target the HIF-1-signaling pathway and ultimately activate HIF-1-dependent neuroprotective genes. This review discusses two interrelated approaches concerning therapy targets in neurodegeneration, sharing in common the implementation of iron chelation activity: antioxidation and HIF-1-pathway activation.

Molecular and cellular mechanisms of pancreatic injury

PURPOSE OF REVIEW

This review focuses on studies from the past year that highlight molecular and cellular mechanisms of pancreatic injury arising from acute and chronic pancreatitis.

RECENT FINDINGS

Factors that induce or ameliorate injury as well as cellular pathways involved have been examined. Causative or sensitizing factors include refluxed bile acids, hypercalcemia, ethanol, hypertriglyceridemia, and acidosis. In addition, the diabetes drug exendin-4 has been associated with pancreatitis, whereas other drugs may reduce pancreatic injury. The intracellular events that influence disease severity are better understood. Cathepsin-L promotes injury through an antiapoptotic effect, rather than by trypsinogen activation. In addition, specific trypsinogen mutations lead to trypsinogen misfolding, endoplasmic reticulum stress, and injury. Endogenous trypsin inhibitors and upregulation of proteins including Bcl-2, fibroblast growth factor 21, and activated protein C can reduce injury. Immune cells, however, have been shown to increase injury via an antiapoptotic effect.

SUMMARY

The current findings are critical to understanding how causative factors initiate downstream cellular events resulting in pancreatic injury. Such knowledge will aid in the development of targeted treatments for pancreatitis. This review will first discuss factors influencing pancreatic injury, and then conclude with studies detailing the cellular mechanisms involved.

Essential role of monocytes and macrophages in the progression of acute pancreatitis

Acute pancreatitis (AP) is an inflammatory condition of the pancreas caused by an imbalance in factors involved in maintaining cellular homeostasis. Earliest events in AP occur within acinar cells accompanied by other principal contributors to the inflammatory response i.e. the endothelial cells, immunocytes (granulocytes, monocytes/macrophages, lymphocytes) and neutrophils. Monocytes/macrophages are important inflammatory mediators, involved in the pathophysiology of AP, known to reside in the peritoneal cavity (in the vicinity of the pancreas) and in peripancreatic tissue. Recent studies suggested that impaired clearance of injured acini by macrophages is associated with an altered cytokine reaction which may constitute a basis for progression of AP. This review focuses on the role of monocytes/macrophages in progression of AP and discusses findings on the inflammatory process involved.