Isolation and culture of mouse primary pancreatic acinar cells

Irisin Ameliorate Acute Pancreatitis and Acinar Cell Viability through Modulation of the Unfolded Protein Response (UPR) and PPARγ-PGC1α-FNDC5 Pathways

Acute pancreatitis (AP) entails pancreatic inflammation, tissue damage and dysregulated enzyme secretion, including pancreatic lipase (PL). The role of irisin, an anti-inflammatory and anti-apoptotic cytokine, in AP and exocrine pancreatic stress is unclear. We have previously shown that irisin regulates PL through the PPARγ-PGC1α-FNDC5 pathway. In this study, we investigated irisin and irisin's pathway on AP in in vitro (AR42J-B13) and ex vivo (rat primary acinar) models using molecular, biochemical and immunohistochemistry methodology. Pancreatitis induction (cerulein (cer)) resulted in a significant up-regulation of the PPARγ-PGC1α-FNDC5 axis, PL expression and secretion and endoplasmic reticulum (ER) stress unfolded protein response (UPR) signal-transduction markers (CHOP, XBP-1 and ATF6). Irisin addition in the cer-pancreatitis state resulted in a significant down-regulation of the PPARγ-PGC1α-FNDC5 axis, PPARγ nucleus-translocation and inflammatory state (TNFα and IL-6) in parallel to diminished PL expression and secretion (in vitro and ex vivo models). Irisin addition up-regulated the expression of pro-survival UPR markers (ATF6 and XBP-1) and reduced UPR pro-apoptotic markers (CHOP) under cer-pancreatitis and induced ER stress (tunicamycin), consequently increasing cells viability. Irisin's pro-survival effect under cer-pancreatitis state was abolished under PPARγ inhibition. Our findings suggest irisin as a potential therapeutic option for AP via its ability to up-regulate pro-survival UPR signals and activate the PPARγ-PGC1α-FNDC5 pathway.

Nardilysin-regulated scission mechanism activates polo-like kinase 3 to suppress the development of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) develops through step-wise genetic and molecular alterations including Kras mutation and inactivation of various apoptotic pathways. Here, we find that development of apoptotic resistance and metastasis of KrasG12D-driven PDAC in mice is accelerated by deleting Plk3, explaining the often-reduced Plk3 expression in human PDAC. Importantly, a 41-kDa Plk3 (p41Plk3) that contains the entire kinase domain at the N-terminus (1-353 aa) is activated by scission of the precursor p72Plk3 at Arg354 by metalloendopeptidase nardilysin (NRDC), and the resulting p32Plk3 C-terminal Polo-box domain (PBD) is removed by proteasome degradation, preventing the inhibition of p41Plk3 by PBD. We find that p41Plk3 is the activated form of Plk3 that regulates a feed-forward mechanism to promote apoptosis and suppress PDAC and metastasis. p41Plk3 phosphorylates c-Fos on Thr164, which in turn induces expression of Plk3 and pro-apoptotic genes. These findings uncover an NRDC-regulated post-translational mechanism that activates Plk3, establishing a prototypic regulation by scission mechanism.

The role of iron and ferroptosis in the pathogenesis of acute pancreatitis

Acute pancreatitis (AP) is an inflammatory disease of the pancreas. Iron is an essential element for life and is involved in many metabolic processes. Ferroptosis is a type of regulated cell death that is triggered by iron and oxidative stress. A well-established mouse AP model was adopted to study the role of iron and ferroptosis in the pathogenesis of pancreatitis. Mice were injected with cerulein to induce AP, and pancreatic tissue samples were analyzed to determine the pathology, cell death, iron deposition, expression of iron transporters, and lipid peroxidation. The role of iron was studied by giving mice extra iron or iron chelator. In vitro studies with acinar cells with ferroptosis activator and inhibitor were also performed to assess the inflammatory response. Iron was found accumulated in the pancreatic tissue of mice who suffered cerulein-induced pancreatitis. Cell death and lipid peroxidation increased in these tissues and could be further modulated by iron dextran or iron chelator. Mice given Hemin through gavage had reduced levels of GSH in pancreatic tissue and increased inflammatory response. Studies with acinar cells showed increased levels of lipid peroxidation and ferroptosis-specific mitochondrial damage when treated with ferroptosis inducer and inflammatory cytokines.

Hematopoietic progenitor kinase 1 inhibits the development and progression of pancreatic intraepithelial neoplasia

Ras plays an essential role in the development of acinar-to-ductal metaplasia (ADM) and pancreatic ductal adenocarcinoma (PDAC). However, mutant Kras is an inefficient driver for PDAC development. The mechanisms of the switching from low Ras activity to high Ras activity that are required for development and progression of pancreatic intraepithelial neoplasias (PanINs) are unclear. In this study, we found that hematopoietic progenitor kinase 1 (HPK1) was upregulated during pancreatic injury and ADM. HPK1 interacted with the SH3 domain and phosphorylated Ras GTPase-activating protein (RasGAP) and upregulated RasGAP activity. Using transgenic mouse models of HPK1 or M46, a kinase-dead mutant of HPK1, we showed that HPK1 inhibited Ras activity and its downstream signaling and regulated acinar cell plasticity. M46 promoted the development of ADM and PanINs. Expression of M46 in KrasG12D Bac mice promoted the infiltration of myeloid-derived suppressor cells and macrophages, inhibited the infiltration of T cells, and accelerated the progression of PanINs to invasive and metastatic PDAC, while HPK1 attenuated mutant Kras-driven PanIN progression. Our results showed that HPK1 plays an important role in ADM and the progression of PanINs by regulating Ras signaling. Loss of HPK1 kinase activity promotes an immunosuppressive tumor microenvironment and accelerates the progression of PanINs to PDAC.

Thiopurines impair the apical plasma membrane expression of CFTR in pancreatic ductal cells via RAC1 inhibition

BACKGROUND AND AIMS

Thiopurine-induced acute pancreatitis (TIP) is one of the most common adverse events among inflammatory bowel disease patients treated with azathioprine (AZA), representing a significant clinical burden. Previous studies focused on immune-mediated processes, however, the exact pathomechanism of TIP is essentially unclear.

METHODS

To model TIP in vivo, we triggered cerulein-induced experimental pancreatitis in mice receiving a daily oral dose of 1.5 mg/kg AZA. Also, freshly isolated mouse pancreatic cells were exposed to AZA ex vivo, and acinar cell viability, ductal and acinar Ca²⁺ signaling, ductal Cl^- and HCO₃^- secretion, as well as cystic fibrosis transmembrane conductance regulator (CFTR) expression were assessed using microscopy techniques. Ras-related C3 botulinum toxin substrate (RAC1) activity was measured with a G-LISA assay. Super-resolution microscopy was used to determine protein colocalization.

RESULTS

We demonstrated that AZA treatment increases tissue damage in the early phase of cerulein-induced pancreatitis in vivo. Also, both per os and ex vivo AZA exposure impaired pancreatic fluid and ductal HCO₃^- and Cl^- secretion, but did not affect acinar cells. Furthermore, ex vivo AZA exposure also inhibited RAC1 activity in ductal cells leading to decreased co-localization of CFTR and the anchor protein ezrin, resulting in impaired plasma membrane localization of CFTR.

CONCLUSIONS

AZA impaired the ductal HCO₃^- and Cl^- secretion through the inhibition of RAC1 activity leading to diminished ezrin-CFTR interaction and disturbed apical plasma membrane expression of CFTR. We report a novel direct toxic effect of AZA on pancreatic ductal cells and suggest that the restoration of ductal function might help to prevent TIP in the future.

Pharmacological inhibition and reversal of pancreatic acinar ductal metaplasia

Pancreatic acinar cells display a remarkable degree of plasticity and can dedifferentiate into ductal-like progenitor cells by a process known as acinar ductal metaplasia (ADM). ADM is believed to be one of the earliest precursor lesions toward the development of pancreatic ductal adenocarcinoma and maintaining the pancreatic acinar cell phenotype suppresses tumor formation. The effects of a novel pStat3 inhibitor (LLL12B) and the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) were investigated using 3-D cultures from p48Cre/+ and p48Cre/+LSL-KrasG12D/+ (KC) mice. LLL12B and TSA inhibited ADM in both KC and p48Cre/+ mouse pancreatic organoids. Furthermore, treatment with LLL12B or TSA on dedifferentiated acini from p48Cre/+ and KC mice that had undergone ADM produced morphologic and gene expression changes that suggest a reversal of ADM. Validation experiments using qRT-PCR (p48Cre/+ and KC) and RNA sequencing (KC) of the LLL12B and TSA treated cultures showed that the ADM reversal was more robust for the TSA treatments. Pathway analysis showed that TSA inhibited Spink1 and PI3K/AKT signaling during ADM reversal. The ability of TSA to reverse ADM was also observed in primary human acinar cultures. We report that pStat3 and HDAC inhibition can attenuate ADM in vitro and reverse ADM in the context of wild-type Kras. Our findings suggest that pharmacological inhibition or reversal of pancreatic ADM represents a potential therapeutic strategy for blocking aberrant ductal reprogramming of acinar cells.

Tricetin Reduces Inflammation and Acinar Cell Injury in Cerulein-Induced Acute Pancreatitis: The Role of Oxidative Stress-Induced DNA Damage Signaling

Acute pancreatitis (AP) poses a worldwide challenge due to the growing incidence and its potentially life-threatening course and complications. Specific targeted therapies are not available, prompting the identification of new pathways and novel therapeutic approaches. Flavonoids comprise several groups of biologically active compounds with wide-ranging effects. The flavone compound, tricetin (TCT), has not yet been investigated in detail but sporadic reports indicate diverse biological activities. In the current study, we evaluated the potential protective effects of TCT in AP. TCT (30 μM) protected isolated primary murine acinar cells from the cytotoxic effects of cerulein, a cholecystokinin analog peptide. The protective effects of TCT were observed in a general viability assay (calcein ester hydrolysis), in an apoptosis assay (caspase activity), and in necrosis assays (propidium iodide uptake and lactate dehydrogenase release). The effects of TCT were not related to its potential antioxidant effects, as TCT did not protect against H₂O₂-induced acinar cell death despite possessing radical scavenging activity. Cerulein-induced expression of IL1β, IL6, and matrix metalloproteinase 2 and activation of nuclear factor-κB (NFκB) were reduced by 30 μM TCT. In vivo experiments confirmed the protective effect of TCT in a mouse model of cerulein-induced AP. TCT suppressed edema formation and apoptosis in the pancreas and reduced lipase and amylase levels in the serum. Moreover, TCT inhibited interleukin-1β (IL1β), interleukin-6 (IL6), and tumor necrosis factor-α (TNFα) expression in the pancreas and reduced the activation of the oxidative DNA damage sensor enzyme poly(ADP-ribose) polymerase-1 (PARP-1). Our data indicate that TCT can be a potential treatment option for AP.

Loss of miR-29a/b1 promotes inflammation and fibrosis in acute pancreatitis

MicroRNA-29 (miR-29) is a critical regulator of fibroinflammatory processes in human diseases. In this study, we found a decrease in miR-29a in experimental and human chronic pancreatitis, leading us to investigate the regulatory role of the miR-29a/b1 cluster in acute pancreatitis (AP) utilizing a conditional miR-29a/b1-KO mouse model. miR-29a/b1-sufficient (WT) and -deficient (KO) mice were administered supramaximal caerulein to induce AP and characterized at different time points, utilizing an array of IHC and biochemical analyses for AP parameters. In caerulein-induced WT mice, miR-29a remained dramatically downregulated at injury. Despite high-inflammatory milieu, fibrosis, and parenchymal disarray in the WT mice during early AP, the pancreata fully restored during recovery. miR-29a/b1-KO mice showed significantly greater inflammation, lymphocyte infiltration, macrophage polarization, and ECM deposition, continuing until late recovery with persistent parenchymal disorganization. The increased pancreatic fibrosis was accompanied by enhanced TGFβ1 coupled with persistent αSMA+ PSC activation. Additionally, these mice exhibited higher circulating IL-6 and inflammation in lung parenchyma. Together, this collection of studies indicates that depletion of miR-29a/b1 cluster impacts the fibroinflammatory mechanisms of AP, resulting in (a) aggravated pathogenesis and (b) delayed recovery from the disease, suggesting a protective role of the molecule against AP.

Loss of the ciliary protein Chibby1 in mice leads to exocrine pancreatic degeneration and pancreatitis

Primary cilia protrude from the apical surface of many cell types and act as a sensory organelle that regulates diverse biological processes ranging from chemo- and mechanosensation to signaling. Ciliary dysfunction is associated with a wide array of genetic disorders, known as ciliopathies. Polycystic lesions are commonly found in the kidney, liver, and pancreas of ciliopathy patients and mouse models. However, the pathogenesis of the pancreatic phenotype remains poorly understood. Chibby1 (Cby1), a small conserved coiled-coil protein, localizes to the ciliary base and plays a crucial role in ciliogenesis. Here, we report that Cby1-knockout (KO) mice develop severe exocrine pancreatic atrophy with dilated ducts during early postnatal development. A significant reduction in the number and length of cilia was observed in Cby1-KO pancreta. In the adult Cby1-KO pancreas, inflammatory cell infiltration and fibrosis were noticeable. Intriguingly, Cby1-KO acinar cells showed an accumulation of zymogen granules (ZGs) with altered polarity. Moreover, isolated acini from Cby1-KO pancreas exhibited defective ZG secretion in vitro. Collectively, our results suggest that, upon loss of Cby1, concomitant with ciliary defects, acinar cells accumulate ZGs due to defective exocytosis, leading to cell death and progressive exocrine pancreatic degeneration after birth.

Betulinic Acid Ameliorates the Severity of Acute Pancreatitis via Inhibition of the NF-κB Signaling Pathway in Mice

Acute pancreatitis (AP) is an inflammatory disorder, involving acinar cell death and the release of inflammatory cytokines. Currently, there are limited effective therapeutic agents for AP. Betulinic acid (BA) is a pentacyclic triterpenoid extracted from Betula platyphylla that has been shown to have anti-inflammatory effects. In this study, we aimed to investigate the effects of BA on AP and elucidate the potential underlying mechanisms. AP was induced in mice through six intraperitoneal injections of cerulein. After the last cerulein injection, the mice were sacrificed. Our results revealed that pre- and post-treatment with BA significantly reduced the severity of pancreatitis, as evidenced by a decrease in histological damage in the pancreas and lung, serum amylase and lipase activity and pancreatic myeloperoxidase activity. Furthermore, BA pretreatment reduced proinflammatory cytokine production, augmentation of chemokines, and infiltration of macrophages and neutrophils in the pancreas of AP mice. In addition, mice that were pretreated with BA showed a reduction in Iκ-Bα degradation and nuclear factor-kappa B (NF-κB) binding activity in the pancreas. Moreover, BA reduced the production of proinflammatory cytokines and NF-κB activation in pancreatic acinar cells (PACs). These findings suggest that BA may have prophylactic and therapeutic effects on AP via inhibition of the NF-κB signaling pathway.

Sulfiredoxin-1 attenuates injury and inflammation in acute pancreatitis through the ROS/ER stress/Cathepsin B axis

Acinar cell injury and the inflammatory response are critical bioprocesses of acute pancreatitis (AP). We investigated the role and underlying mechanism of sulfiredoxin-1 (Srxn1) in AP. Mild AP was induced by intraperitoneal injection of cerulein and severe AP was induced by partial duct ligation with cerulein stimulation or intraperitoneal injection of L-arginine in mice. Acinar cells, neutrophils, and macrophages were isolated. The pancreas was analyzed by histology, immunochemistry staining, and TUNEL assays, and the expression of certain proteins and RNAs, cytokine levels, trypsin activity, and reactive oxygen species (ROS) levels were determined. Srxn1 was inhibited by J14 or silenced by siRNA, and overexpression was introduced by a lentiviral vector. Transcriptomic analysis was used to explore the mechanism of Srxn1-mediated effects. We also evaluated the effect of adeno-associated virus (AAV)-mediated overexpression of Srxn1 by intraductal administration and the protection of AP. We found that Srxn1 expression was upregulated in mild AP but decreased in severe AP. Inhibition of Srxn1 increased ROS, histological score, the release of trypsin, and inflammatory responses in mice. Inhibition of Srxn1 expression promoted the production of ROS and induced apoptosis, while overexpression of Srxn1 led to the opposite results in acinar cells. Furthermore, inhibition of Srxn1 expression promoted the inflammatory response by accumulating and activating M1 phenotype macrophages and neutrophils in AP. Mechanistically, ROS-induced ER stress and activation of Cathepsin B, which converts trypsinogen to trypsin, were responsible for the Srxn1 inhibition-mediated effects on AP. Importantly, we demonstrated that AAV-mediated overexpression of Srxn1 attenuated AP in mice. Taken together, these results showed that Srxn1 is a protective target for AP by attenuating acinar injury and inflammation through the ROS/ER stress/Cathepsin B axis.

Mifepristone (RU486) inhibits dietary lipid digestion by antagonizing the role of glucocorticoid receptor on lipase transcription

Lipid digestion and absorption are tightly regulated to cope with metabolic demands among tissues. How these processes are coordinated is not well characterized. Here, we found that mifepristone (RU486) prevents lipid digestion both in flies and mice. In flies, RU486 administration suppresses lipid digestion by transcriptional downregulating Magro in guts. Similarly, intestinal lipid uptake in mice was also suppressed by RU486 through the glucocorticoid receptor (GR). Further studies showed that the pancreatic lipase Pnlip is a direct transcriptional target of GR in pancreas tissues. Glucocorticoid levels in mice fed a high fat diet (HFD) are significantly lower than those fed on a conventional diet, and RU486 administration inhibits HFD-induced obesity both in mice and flies. Our findings identified a novel mechanism of RU486 functions as a GR antagonist systematically regulating lipid metabolism, providing new insight on the role of Glucocorticoid/GR in Cushing disease, diabetes, and other related metabolic syndromes.

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RU486 suppresses lipid digestion both in mice and flies.

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In flies, lipase Magro is transcriptionally suppressed by RU486 through dERR.

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In mice, intestinal lipid digestion is inhibited by RU486 through (GR)/PTL pathway in pancreas.

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RU486 alleviates high fat diet-induced obesity both in flies and mice.

Pancreatic glycoprotein 2 is a first line of defense for mucosal protection in intestinal inflammation

Increases in adhesive and invasive commensal bacteria, such as Escherichia coli, and subsequent disruption of the epithelial barrier is implicated in the pathogenesis of inflammatory bowel disease (IBD). However, the protective systems against such barrier disruption are not fully understood. Here, we show that secretion of luminal glycoprotein 2 (GP2) from pancreatic acinar cells is induced in a TNF-dependent manner in mice with chemically induced colitis. Fecal GP2 concentration is also increased in Crohn's diease patients. Furthermore, pancreas-specific GP2-deficient colitis mice have more severe intestinal inflammation and a larger mucosal E. coli population than do intact mice, indicating that digestive-tract GP2 binds commensal E. coli, preventing epithelial attachment and penetration. Thus, the pancreas-intestinal barrier axis and pancreatic GP2 are important as a first line of defense against adhesive and invasive commensal bacteria during intestinal inflammation.

Mesenchyme-derived IGF2 is a major paracrine regulator of pancreatic growth and function

The genetic mechanisms that determine the size of the adult pancreas are poorly understood. Imprinted genes, which are expressed in a parent-of-origin-specific manner, are known to have important roles in development, growth and metabolism. However, our knowledge regarding their roles in the control of pancreatic growth and function remains limited. Here we show that many imprinted genes are highly expressed in pancreatic mesenchyme-derived cells and explore the role of the paternally-expressed insulin-like growth factor 2 (Igf2) gene in mesenchymal and epithelial pancreatic lineages using a newly developed conditional Igf2 mouse model. Mesenchyme-specific Igf2 deletion results in acinar and beta-cell hypoplasia, postnatal whole-body growth restriction and maternal glucose intolerance during pregnancy, suggesting that the mesenchyme is a developmental reservoir of IGF2 used for paracrine signalling. The unique actions of mesenchymal IGF2 are demonstrated by the absence of any discernible growth or functional phenotypes upon Igf2 deletion in the developing pancreatic epithelium. Additionally, increased IGF2 levels specifically in the mesenchyme, through conditional Igf2 loss-of-imprinting or Igf2r deletion, leads to pancreatic acinar overgrowth. Furthermore, ex-vivo exposure of primary acinar cells to exogenous IGF2 activates AKT, a key signalling node, and increases their number and amylase production. Based on these findings, we propose that mesenchymal Igf2, and perhaps other imprinted genes, are key developmental regulators of adult pancreas size and function.

Organotypic Culture of Acinar Cells for the Study of Pancreatic Cancer Initiation

The carcinogenesis of pancreatic ductal adenocarcinoma (PDA) progresses according to multi-step evolution, whereby the disease acquires increasingly aggressive pathological features. On the other hand, disease inception is poorly investigated. Decoding the cascade of events that leads to oncogenic transformation is crucial to design strategies for early diagnosis as well as to tackle tumor onset. Lineage-tracing experiments demonstrated that pancreatic cancerous lesions originate from acinar cells, a highly specialized cell type in the pancreatic epithelium. Primary acinar cells can survive in vitro as organoid-like 3D spheroids, which can transdifferentiate into cells with a clear ductal morphology in response to different cell- and non-cell-autonomous stimuli. This event, termed acinar-to-ductal metaplasia, recapitulates the histological and molecular features of disease initiation. Here, we will discuss the isolation and culture of primary pancreatic acinar cells, providing a historical and technical perspective. The impact of pancreatic cancer research will also be debated. In particular, we will dissect the roles of transcriptional, epigenetic, and metabolic reprogramming for tumor initiation and we will show how that can be modeled using ex vivo acinar cell cultures. Finally, mechanisms of PDA initiation described using organotypical cultures will be reviewed.

Protocol for Studying Reprogramming of Mouse Pancreatic Acinar Cells to β-like Cells

The potential of reprogrammed β cells derived from pancreatic exocrine cells to treat diabetes has been demonstrated in animal models. However, the precise mechanisms and regulators involved in this process are not clear. Here, we describe a method that allows mechanistic studies of this process in primary exocrine cultures using adenoviral expression vectors. This rapid 5-day protocol, provides the researcher with a highly controlled experimental system in which the effects of different compounds or genetic manipulations can be studied. For complete details on the use and execution of this protocol, please refer to Elhanani et al. (2020).

Two-layer regulation of TRAF6 mediated by both TLR4/NF-kB signaling and miR-589-5p increases proinflammatory cytokines in the pathology of severe acute pancreatitis

Inflammation is a leading cause of severe acute pancreatitis (SAP). MicroRNAs (miRNAs) are emerging as important regulators involved in the pathogenesis of many diseases including pancreatitis. To identify miRNAs that contribute to the pathology of SAP, we carried out a miRNA-specific microarray analysis using the biopsies donated by SAP patients. We totally obtained 50 differentially expressed miRNAs, including 20 upregulated and 30 downregulated miRNAs, respectively. We focused our current study on revealing the downstream target and the upstream regulatory mechanism of miR-589-5p, the most downregulated miRNA in our candidate lists. Our prediction results indicated that miR-589-5p might target TRAF6 (tumor necrosis factor receptor-associated factor 6), a critical member of the TLR4/NF-kB (Toll-like receptor 4/nuclear transcription factor-kB) pathway. Using different strategies such as in vitro overexpression or downregulation of miR-589-5p and treatment with lipopolysaccharide (LPS), we found that the expression of TRAF6 was regulated by two-layer mechanisms. On the one hand, TRAF6 was transcriptionally controlled by a DNA methylation mediated downregulation of miR-589-5p. On the other hand, the activation of TLR4/NF-kB signaling also could increase the protein level of TRAF6. The increased TRAF6 aggravated the downstream signaling and caused the translocation of NF-kB subunits from the cytoplasm to the nucleus, where NF-kB transcription factors induced the expression of proinflammatory cytokine genes. The maturation and production of proinflammatory cytokines induced inflammatory response and caused the occurrence of SAP.

Novel mitochondrial transition pore inhibitor N-methyl-4-isoleucine cyclosporin is a new therapeutic option in acute pancreatitis

KEY POINTS

•Bile acids, ethanol and fatty acids affect pancreatic ductal fluid and bicarbonate secretion via mitochondrial damage, ATP depletion and calcium overload. •Pancreatitis-inducing factors open the membrane transition pore (mPTP) channel via cyclophilin D activation in acinar cells, causing calcium overload and cell death; genetic or pharmacological inhibition of mPTP improves the outcome of acute pancreatitis in animal models. •Here we show that genetic and pharmacological inhibition of mPTP protects mitochondrial homeostasis and cell function evoked by pancreatitis-inducing factors in pancreatic ductal cells. •The results also show that the novel cyclosporin A derivative NIM811 protects mitochondrial function in acinar and ductal cells, and it preserves bicarbonate transport mechanisms in pancreatic ductal cells. •We found that NIM811 is highly effective in different experimental pancreatitis models and has no side-effects. NIM811 is a highly suitable compound to be tested in clinical trials.

ABSTRACT

Mitochondrial dysfunction plays a crucial role in the development of acute pancreatitis (AP); however, no compound is currently available with clinically acceptable effectiveness and safety. In this study, we investigated the effects of a novel mitochondrial transition pore inhibitor, N-methyl-4-isoleucine cyclosporin (NIM811), in AP. Pancreatic ductal and acinar cells were isolated by enzymatic digestion from Bl/6 mice. In vitro measurements were performed by confocal microscopy and microfluorometry. Preventative effects of pharmacological [cylosporin A (2 µm), NIM811 (2 µm)] or genetic (Ppif^-/- /Cyp D KO) inhibition of the mitochondrial transition pore (mPTP) during the administration of either bile acids (BA) or ethanol + fatty acids (EtOH+FA) were examined. Toxicity of mPTP inhibition was investigated by detecting apoptosis and necrosis. In vivo effects of the most promising compound, NIM811 (5 or 10 mg kg^-1 per os), were checked in three different AP models induced by either caerulein (10 × 50 µg kg^-1 ), EtOH+FA (1.75 g kg^-1 ethanol and 750 mg kg^-1 palmitic acid) or 4% taurocholic acid (2 ml kg^-1 ). Both genetic and pharmacological inhibition of Cyp D significantly prevented the toxic effects of BA and EtOH+FA by restoring mitochondrial membrane potential (Δψ) and preventing the loss of mitochondrial mass. In vivo experiments revealed that per os administration of NIM811 has a protective effect in AP by reducing oedema, necrosis, leukocyte infiltration and serum amylase level in AP models. Administration of NIM811 had no toxic effects. The novel mitochondrial transition pore inhibitor NIM811 thus seems to be an exceptionally good candidate compound for clinical trials in AP.

Interleukin 22 disrupts pancreatic function in newborn mice expressing IL-23

Neonatal inflammatory diseases are associated with severe morbidity, but the inflammatory factors underlying them and their potential effector mechanisms are poorly defined. Here we show that necrotizing enterocolitis in neonate mice is accompanied by elevation of IL-23 and IL-22 and decreased production of pancreatic enzymes. These phenotypes are mirrored in neonate mice overexpressing IL-23 in CX3CR1+ myeloid cells or in keratinocytes. The mice fail to grow and die prematurely, displaying systemic inflammation, nutrient malabsorption and decreased expression of intestinal and pancreatic genes mediating digestion and absorption of carbohydrates, proteins, and lipids. Germ-free environment improves, and genetic ablation of IL-22 restores normal growth in mice overexpressing IL-23. Mechanistically, IL-22 acts directly at the level of pancreatic acinar cells to decrease expression of the pancreas associated transcription factor 1a (PTF1a). These results show that augmented production of IL-23 and IL-22 in early life has a negative impact on pancreatic enzyme secretion and food absorption.

Large triglyceride-rich lipoproteins in hypertriglyceridemia are associated with the severity of acute pancreatitis in experimental mice

Hypertriglyceridemia severity is linked to acute pancreatitis prognosis, but it remains unknown why a portion of severe hypertriglyceridemia patients do not develop severe acute pancreatitis. To investigate whether hypertriglyceridemia subtypes affect acute pancreatitis progression, we analyzed two genetically modified hypertriglyceridemia mouse models—namely, glycosylphosphatidylinositol high-density lipoprotein binding protein 1 knockout (Gpihbp1−/−) and apolipoprotein C3 transgenic (ApoC3-tg) mice. Acute pancreatitis was induced by 10 intraperitoneal caerulein injections. Biochemical assays and pathological analysis were performed for the severity evaluation of acute pancreatitis. Plasma triglyceride-rich lipoproteins (TRLs), including chylomicrons and very low-density lipoprotein (VLDL), were collected via ultracentrifugation to evaluate their cytotoxic effects on primary pancreatic acinar cells (PACs). We found that the particle sizes of Gpihbp1−/− TRLs were larger than ApoC3-tg TRLs. Severe pancreatic injury with large areas of pancreatic necrosis in the entire lobule was induced in Gpihbp1−/− mice when plasma triglyceride levels were greater than 2000 mg/dL. However, ApoC3-tg mice with the same triglyceride levels did not develop large areas of pancreatic necrosis, even upon the administration of poloxamer 407 to further increase triglyceride levels. Meanwhile, in the acute pancreatitis model, free fatty acids (FFAs) in the pancreas of Gpihbp1−/− mice were greater than in ApoC3-tg mice. TRLs from Gpihbp1−/− mice released more FFAs and were more toxic to PACs than those from ApoC3-tg mice. Chylomicrons from patients showed the same effects on PACs as TRLs from Gpihbp1−/− mice. Gpihbp1−/− mice with triglyceride levels below 2000 mg/dL had milder pancreatic injury and less incidence of pancreatic necrosis than those with triglyceride levels above 2000 mg/dL, similar to Gpihbp1−/−mice with triglyceride levels above 2000 mg/dL but with fenofibrate administration. These findings demonstrated that hypertriglyceridemia subtypes with large TRL particles could affect acute pancreatitis progression and that chylomicrons showed more cytotoxicity than VLDL by releasing more FFAs.

Tamoxifen affects chronic pancreatitis-related fibrogenesis in an experimental mouse model: an effect beyond Cre recombination

Tamoxifen is very successfully used for the induction of Cre^ERT‐mediated genomic recombination in conditional mouse models. Recent studies, however, indicated that tamoxifen might also affect the fibrotic response in several disease models following administration, both in vitro and in vivo. In order to investigate a possible effect of tamoxifen on pancreatic fibrogenesis and to evaluate an optimal treatment scheme in an experimental pancreatitis mouse model, we administered tamoxifen by oral gavage to both male and female C57BL/6J mice and then waited for different periods of time before inducing chronic pancreatitis by cerulein. We observed a sex‐specific and time‐dependent effect of tamoxifen on the fibrotic response as measured by collagen deposition and the number of myofibroblasts and macrophages. The findings of in vitro studies, in which cerulein was administrated with or without 4‐hydroxytamoxifen to stimulate primary murine female and male pancreatic stellate cells, supported our in vivo observations. Real‐time PCR also indicated that this effect may be related to differences in ERα expression between female and male stellate cells. Our data demonstrate that tamoxifen administration has unignorable side effects, which affect the experimental outcome in a cerulein‐based model of chronic pancreatitis in mice. We suggest a 2‐week waiting period before cerulein administration to reduce side effects to a minimum for the described fibrosis model in female mice.

Concise Review: A Critical Evaluation of Criteria Used to Define Salivary Gland Stem Cells

In the effort to develop cell-based therapies to treat salivary gland dysfunction, many different populations of cells in the adult salivary glands have been proposed as stem cells. These cell populations vary, depending on the assay used, and are often nonoverlapping, leading to the conclusion that salivary glands harbor multiple stem cells. The goal of this review is to critically appraise the assays and properties used to identify stem cells in the adult salivary gland, and to consider the caveats of each. Re-evaluation of the defining criteria may help to reconcile the many potential stem cell populations described in the salivary gland, in order to increase comparability between studies and build consensus in the field. Stem Cells 2019;37:1144-1150.

High Glucose Triggers Nucleotide Imbalance through O-GlcNAcylation of Key Enzymes and Induces KRAS Mutation in Pancreatic Cells

KRAS mutations are the earliest events found in approximately 90% of pancreatic ductal adenocarcinomas (PDACs). However, little is known as to why KRAS mutations preferentially occur in PDACs and what processes/factors generate these mutations. While abnormal carbohydrate metabolism is associated with a high risk of pancreatic cancer, it remains elusive whether a direct relationship between KRAS mutations and sugar metabolism exists. Here, we show that under high-glucose conditions, cellular O-GlcNAcylation is significantly elevated in pancreatic cells that exhibit lower phosphofructokinase (PFK) activity than other cell types. This post-translational modification specifically compromises the ribonucleotide reductase (RNR) activity, leading to deficiency in dNTP pools, genomic DNA alterations with KRAS mutations, and cellular transformation. These results establish a mechanistic link between a perturbed sugar metabolism and genomic instability that induces de novo oncogenic KRAS mutations preferentially in pancreatic cells.

Mimicking and Manipulating Pancreatic Acinar-to-Ductal Metaplasia in 3-dimensional Cell Culture

The differentiation of acinar cells to ductal cells during pancreatitis and in the early development of pancreatic cancer is a key process that requires further study. To understand the mechanisms regulating acinar-to-ductal metaplasia (ADM), ex vivo 3D culture and differentiation of primary acinar cells to ductal cells offers many advantages over other systems. With the technique herein, modulation of protein expression is simple and quick, requiring only one day to isolate, stimulate or virally infect, and begin culturing primary acinar cells to investigate the ADM process. In contrast to using basement membrane matrix, the seeding of acinar cell clusters in collagen I extracellular matrix, allows acinar cells to retain their acinar identity before manipulation. This is vital when testing the contribution of various components to the induction of ADM. Not only are the effects of cytokines or other ectopically administered factors testable through this technique, but the contribution of common mutations, increased protein expression, or knockdown of protein expression is testable via viral infection of primary acinar cells, using adenoviral or lentiviral vectors. Moreover, cells can be re-isolated from collagen or basement membrane matrix at the endpoint and analyzed for protein expression.

MARCKS phosphorylation and amylase release in GLP-1-stimulated acini isolated from rat pancreas

Little is known about the effects of glucagon-like peptide 1 (GLP-1) on the pancreatic exocrine gland. In the gland, secretagogues induce amylase release. That signal transduction is evoked mainly by an increase in intracellular Ca2+ levels and activation of protein kinase C (PKC). We previously demonstrated that myristoylated alanine-rich C kinase substrate (MARCKS), a PKC substrate, is involved in pancreatic amylase release. Here, we studied the effects of GLP-1 on MARCKS phosphorylation and amylase release in rat pancreatic acini. GLP-1 induced amylase release and MARCKS phosphorylation in isolated pancreatic acini. Inhibitors of cAMP-dependent protein kinase (PKA) suppressed those effects. Furthermore, a MARCKS-related peptide inhibited the GLP-1-induced amylase release. These findings suggest that GLP-1 induces amylase release through MARCKS phosphorylation via activation of PKA in isolated pancreatic acini.

Loss of complex O-glycosylation impairs exocrine pancreatic function and induces MODY8-like diabetes in mice

Cosmc is ubiquitously expressed and acts as a specific molecular chaperone assisting the folding and stability of core 1 synthase. Thus, it plays a crucial role in the biosynthesis of O-linked glycosylation of proteins. Here, we show that ablation of Cosmc in the exocrine pancreas of mice causes expression of truncated O-glycans (Tn antigen), resulting in exocrine pancreatic insufficiency with decreased activities of digestive enzymes and diabetes. To understand the molecular causes of the pleiotropic phenotype, we used Vicia villosa agglutinin to enrich Tn antigen-modified proteins from Cosmc-KO pancreatic lysates and performed a proteomic analysis. Interestingly, a variety of proteins were identified, of which bile salt-activated lipase (also denoted carboxyl-ester lipase, Cel) was the most abundant. In humans, frameshift mutations in CEL cause maturity-onset diabetes of the young type 8 (MODY8), a monogenic syndrome of diabetes and pancreatic exocrine dysfunction. Here, we provide data suggesting that differentially O-glycosylated Cel could negatively affect beta cell function. Taken together, our findings demonstrate the importance of correct O-glycan formation for normal exocrine and endocrine pancreatic function, implying that aberrant O-glycans might be relevant for pathogenic mechanisms of the pancreas.

TSG-6 secreted by human adipose tissue-derived mesenchymal stem cells ameliorates severe acute pancreatitis via ER stress downregulation in mice

Background

Through recent studies, the onset of acute pancreatitis in pancreatic acinar cells (PACs) and the regulatory role of PACs in severe acute pancreatitis (SAP) have been revealed. During the early stages of pancreatitis, the endoplasmic reticulum (ER) in PACs undergoes significant changes, including swelling and vacuolization. In response to an increase in the extracellular stress in ER, PACs lose their functions, leading to cell apoptosis and inflammation response. The beneficial effects of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) on SAP have been well documented in previous studies. However, the underlying mechanism of their action remains controversial.

Methods

In this study, the therapeutic effects of intraperitoneally administered hAT-MSCs in a caerulein (50 μg/kg)- and lipopolysaccharide (LPS) (10 mg/kg)-co-induced SAP mouse model were evaluated. Inflammatory response and ER stress were measured in pancreatic tissue samples, and the beneficial effects were evaluated through quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot, and immunofluorescence analysis.

Results

Inflammatory response and ER stress were ameliorated following hAT-MSC injection, and the beneficial effects were observed in the absence of significant engraftment of hAT-MSCs. hAT-MSCs transfected with siRNA-targeting tumour necrosis factor-α-induced gene/protein 6 (TSG-6) were unable to inhibit ER stress and inflammation. In addition, TSG-6 from hAT-MSCs significantly suppressed ER stress-induced apoptosis and nuclear factor kappa B (NF-κB) activity in SAP model mice.

Conclusions

TSG-6 secreted by hAT-MSCs protects PACs in SAP model mice via the inhibition of ER stress, as well as inflammatory responses. This study has revealed a new area for ER stress-targeted therapy in SAP patients.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1009-8) contains supplementary material, which is available to authorized users.

PINK1 and PARK2 Suppress Pancreatic Tumorigenesis through Control of Mitochondrial Iron-Mediated Immunometabolism

Pancreatic cancer is an aggressive malignancy with changes in the tumor microenvironment. Here, we demonstrate that PINK1 and PARK2 suppressed pancreatic tumorigenesis through control of mitochondrial iron-dependent immunometabolism. Using mouse models of spontaneous pancreatic cancer, we show that depletion of Pink1 and Park2 accelerates mutant Kras-driven pancreatic tumorigenesis. PINK1-PARK2 pathway-mediated degradation of SLC25A37 and SLC25A28 increases mitochondrial iron accumulation, which leads to the HIF1A-dependent Warburg effect and AIM2-dependent inflammasome activation in tumor cells. AIM2-mediated HMGB1 release further induces expression of CD274/PD-L1. Consequently, pharmacological administration of mitochondrial iron chelator, anti-HMGB1 antibody, or genetic depletion of Hif1a or Aim2 in pink1^-/- and park2^-/- mice confers protection against pancreatic tumorigenesis. Low PARK2 expression and high SLC25A37 and AIM2 expression are associated with poor prognosis in patients with pancreatic cancer. These findings suggest that disrupted mitochondrial iron homeostasis may contribute to cancer development and hence constitute a target for therapeutic intervention.

Thioredoxin system-mediated regulation of mutant Kras associated pancreatic neoplasia and cancer

Peroxiredoxin-1 (Prdx1), a member of the thioredoxin (Txn) system, is overexpressed and correlates with poor prognosis in pancreatic cancer patients and can suppress Kras signaling through redox-mediated inhibition of ERK and AKT in lung and breast cancer. Its redox function is maintained by Txn and sulfiredoxin (Srxn), and its tumor promoting functions are activated by post-translational modification. We studied the role of the Txn system in pancreatic neoplasia and cancer by determining how it regulates the phosphorylation of Kras effectors and by determining its association with patient survival. We found that elevated Prdx1 nuclear localization significantly correlated with better patient survival. Our data also demonstrate that the expression of the Txn system is dysregulated, with elevated Prdx1 expression and significantly decreased Txn and Srxn expression in pancreatic lesions of targeted mutant Kras mouse models. This correlated with distinct differences in the interconversion of Prdx1 oligomers that affect its ability to regulate ERK and AKT phosphorylation. Our data also suggest that Prdx1 post-translational modification and oligomerization suppress Prdx1 mediated redox regulation of ERK phosphorylation. We observed distinct differences in Txn expression and in the ability of pTyr-Prdx1 to bind to pERK in a PanIN model of pancreatic neoplasia as compared to an IPMN model, indicating a distinct difference in the function of post-translationally modified Prdx1 in cells with less Txn expression. Modified Txn system function and post-translational regulation may therefore play a significant role in pancreatic tumorigenesis by altering Kras effector phosphorylation and inhibiting the tumor suppressive redox functions of Prdx1.

Targeting reactive nitrogen species suppresses hereditary pancreatic cancer

Germline mutation of BRCA2 induces hereditary pancreatic cancer. However, how BRCA2 mutation specifically induces pancreatic tumorigenesis remains elusive. Here, we have examined a mouse model of Brca2-deficiency-induced pancreatic tumors and found that excessive reactive nitrogen species (RNS), such as nitrite, are generated in precancerous pancreases, which induce massive DNA damage, including DNA double-strand breaks. RNS-induced DNA lesions cause genomic instability in the absence of Brca2. Moreover, with the treatment of antioxidant tempol to suppress RNS, not only are DNA lesions significantly reduced, but also the onset of pancreatic cancer is delayed. Thus, this study demonstrates that excess RNS are a nongenetic driving force for Brca2-deficiency-induced pancreatic tumors. Suppression of RNS could be an important strategy for pancreatic cancer prevention.

GRP78 haploinsufficiency suppresses acinar-to-ductal metaplasia, signaling, and mutant Kras-driven pancreatic tumorigenesis in mice

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal disease in critical need of new therapeutic strategies. Here, we report that the stress-inducible 78-kDa glucose-regulated protein (GRP78/HSPA5), a key regulator of endoplasmic reticulum homeostasis and PI3K/AKT signaling, is overexpressed in the acini and PDAC of Pdx1-Cre;Kras^G12D/+;p53^f/+ (PKC) mice as early as 2 mo, suggesting that GRP78 could exert a protective effect on acinar cells under stress, as during PDAC development. The PKC pancreata bearing wild-type Grp78 showed detectable PDAC by 3 mo and rapid subsequent tumor growth. In contrast, the PKC pancreata bearing a Grp78^f/+ allele (PKC78^f/+ mice) expressing about 50% of GRP78 maintained normal sizes during the early months, with reduced proliferation and suppression of AKT, S6, ERK, and STAT3 activation. Acinar-to-ductal metaplasia (ADM) has been identified as a key tumor initiation mechanism of PDAC. Compared with PKC, the PKC78^f/+ pancreata showed substantial reduction of ADM as well as pancreatic intraepithelial neoplasia-1 (PanIN-1), PanIN-2, and PanIN-3 and delayed onset of PDAC. ADM in response to transforming growth factor α was also suppressed in ex vivo cultures of acinar cell clusters isolated from mouse pancreas bearing targeted heterozygous knockout of Grp78 (c78^f/+ ) and subjected to 3D culture in collagen. We further discovered that GRP78 haploinsufficiency in both the PKC78^f/+ and c78^f/+ pancreata leads to reduction of epidermal growth factor receptor, which is critical for ADM initiation. Collectively, our studies establish a role for GRP78 in ADM and PDAC development.

Isolating and Analyzing Cells of the Pancreas Mesenchyme by Flow Cytometry

The pancreas is comprised of epithelial cells that are required for food digestion and blood glucose regulation. Cells of the pancreas microenvironment, including endothelial, neuronal, and mesenchymal cells were shown to regulate cell differentiation and proliferation in the embryonic pancreas. In the adult, the function and mass of insulin-producing cells were shown to depend on cells in their microenvironment, including pericyte, immune, endothelial, and neuronal cells. Lastly, changes in the pancreas microenvironment were shown to regulate pancreas tumorigenesis. However, the cues underlying these processes are not fully defined. Therefore, characterizing the different cell types that comprise the pancreas microenvironment and profiling their gene expression are crucial to delineate the tissue development and function under normal and diseased states. Here, we describe a method that allows for the isolation of mesenchymal cells from the pancreas of embryonic, neonatal, and adult mice. This method utilizes the enzymatic digestion of mouse pancreatic tissue and the subsequent fluorescence-activated cell sorting (FACS) or flow-cytometric analysis of labeled cells. Cells can be labeled by either immunostaining for surface markers or by the expression of fluorescent proteins. Cell isolation can facilitate the characterization of genes and proteins expressed in cells of the pancreas mesenchyme. This protocol was successful in isolating and culturing highly enriched mesenchymal cell populations from the embryonic, neonatal, and adult mouse pancreas.

Intravenous hMSCs Ameliorate Acute Pancreatitis in Mice via Secretion of Tumor Necrosis Factor-α Stimulated Gene/Protein 6

The administration of mesenchymal stem cells/multipotent mesenchymal stromal cells (MSCs) to enhance tissue repair is currently undergoing clinical trials. Some studies, including our previous work, have also revealed the beneficial effect of MSCs in severe acute pancreatitis (SAP); however, their mechanisms or mode of action remain controversial. In this study, we demonstrated that intravenously (i.v.)-administered human MSCs (hMSCs) remarkably promoted recovery from experimental SAP without significant engraftment of hMSCs in the damaged pancreas. Interestingly, we found that i.v.-administered hMSCs with knockdown of TSG-6 expression lost most of their anti-inflammatory effects and thus could not significantly ameliorate SAP. As expected, the effects of hMSCs were also duplicated by i.v. infusion of recombinant TSG-6. Furthermore, our results showed that the increase of oxidative stress, activation of the NLRP3 inflammasome and NF-κB signaling in SAP was substantially inhibited following administration of hMSCs or TSG-6, which was dependent on the presence of CD-44 receptors in acinar cells. In conclusion, our study, for the first time, revealed that novel mechanisms are responsible for the immunomodulatory effect of i.v. hMSCs.

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.

Nucleotide-binding oligomerization domain 1 acts in concert with the cholecystokinin receptor agonist, cerulein, to induce IL-33-dependent chronic pancreatitis

Nucleotide-binding oligomerization domain 1 (NOD1) fulfills important host-defense functions via its responses to a variety of gut pathogens. Recently, however, we showed that in acute pancreatitis caused by administration of cholecystokinin receptor (CCKR) agonist (cerulein) NOD1 also has a role in inflammation via its responses to gut commensal organisms. In the present study, we explored the long-term outcome of such NOD1 responsiveness in a new model of chronic pancreatitis induced by repeated administration of low doses of cerulein in combination with NOD1 ligand. We found that the development of chronic pancreatitis in this model requires intact NOD1 and type I IFN signaling and that such signaling mediates a macrophage-mediated inflammatory response that supports interleukin (IL)-33 production by acinar cells. The IL-33, in turn, has a necessary role in the induction of IL-13 and TGF-β1, factors causing the fibrotic reaction characteristic of chronic pancreatitis. Interestingly, the Th2 effects of IL-33 were attenuated by the concomitant type I IFN response since the inflammation was marked by clear increases in IFN-γ and TNF-α production but only marginal increases in IL-4 production. These studies establish chronic pancreatitis as an IL-33-dependent inflammation resulting from synergistic interactions between the NOD1 and CCKR signaling pathways.

AID-expressing epithelium is protected from oncogenic transformation by an NKG2D surveillance pathway

Activation-induced deaminase (AID) initiates secondary antibody diversification in germinal center B cells, giving rise to higher affinity antibodies through somatic hypermutation (SHM) or to isotype-switched antibodies through class switch recombination (CSR). SHM and CSR are triggered by AID-mediated deamination of cytosines in immunoglobulin genes. Importantly, AID activity in B cells is not restricted to Ig loci and can promote mutations and pro-lymphomagenic translocations, establishing a direct oncogenic mechanism for germinal center-derived neoplasias. AID is also expressed in response to inflammatory cues in epithelial cells, raising the possibility that AID mutagenic activity might drive carcinoma development. We directly tested this hypothesis by generating conditional knock-in mouse models for AID overexpression in colon and pancreas epithelium. AID overexpression alone was not sufficient to promote epithelial cell neoplasia in these tissues, in spite of displaying mutagenic and genotoxic activity. Instead, we found that heterologous AID expression in pancreas promotes the expression of NKG2D ligands, the recruitment of CD8⁺ T cells, and the induction of epithelial cell death. Our results indicate that AID oncogenic potential in epithelial cells can be neutralized by immunosurveillance protective mechanisms.

Slug inhibits pancreatic cancer initiation by blocking Kras-induced acinar-ductal metaplasia

Cells in the pancreas that have undergone acinar-ductal metaplasia (ADM) can transform into premalignant cells that can eventually become cancerous. Although the epithelial-mesenchymal transition regulator Snail (Snai1) can cooperate with Kras in acinar cells to enhance ADM development, the contribution of Snail-related protein Slug (Snai2) to ADM development is not known. Thus, transgenic mice expressing Slug and Kras in acinar cells were generated. Surprisingly, Slug attenuated Kras-induced ADM development, ERK1/2 phosphorylation and proliferation. Co-expression of Slug with Kras also attenuated chronic pancreatitis-induced changes in ADM development and fibrosis. In addition, Slug attenuated TGF-α-induced acinar cell metaplasia to ductal structures and TGF-α-induced expression of ductal markers in ex vivo acinar explant cultures. Significantly, blocking the Rho-associated protein kinase ROCK1/2 in the ex vivo cultures induced expression of ductal markers and reversed the effects of Slug by inducing ductal structures. In addition, blocking ROCK1/2 activity in Slug-expressing Kras mice reversed the inhibitory effects of Slug on ADM, ERK1/2 phosphorylation, proliferation and fibrosis. Overall, these results increase our understanding of the role of Slug in ADM, an early event that can eventually lead to pancreatic cancer development.

Ablation of huntingtin in adult neurons is nondeleterious but its depletion in young mice causes acute pancreatitis

The Huntington's disease (HD) protein, huntingtin (HTT), is essential for early development. Because suppressing the expression of mutant HTT is an important approach to treat the disease, we must first understand the normal function of Htt in adults versus younger animals. Using inducible Htt knockout mice, we found that Htt depletion does not lead to adult neurodegeneration or animal death at >4 mo of age, which was also verified by selectively depleting Htt in neurons. On the other hand, young Htt KO mice die at 2 mo of age of acute pancreatitis due to the degeneration of pancreatic acinar cells. Importantly, Htt interacts with the trypsin inhibitor, serine protease inhibitor Kazal-type 3 (Spink3), to inhibit activation of digestive enzymes in acinar cells in young mice, and transgenic HTT can rescue the early death of Htt KO mice. These findings point out age- and cell type-dependent vital functions of Htt and the safety of knocking down neuronal Htt expression in adult brains as a treatment.

In vitro secretion of zymogens by bovine pancreatic acini and ultra-structural analysis of exocytosis

The aim of this study is to establish a bovine pancreatic acinar cell culture model with longer viability and functionality. The cells could be maintained in a functional state for upto 20 days with normal morphology. Cells were positive for amylase as observed by immunofluorescence staining. Acinar cells are spherical and range about 2–3 µm in diameter. The porosome formed by exocytosis and heterogenous enzyme granules of size ranging 100–300 nm were seen on the surface of cells by electron microscopy. The activity of the enzymes was high on day 15 and the activity profile of the enzymes is in the order: protease>lipase>amylase and the enzymes were identified by SDS-PAGE. Long-term culture of bovine pancreatic acini could be useful in studying the pathogenesis of pancreatitis. Since the bovine genome shares about 80% identity with the human genome, the cells derived from bovine pancreas can be engineered and used as a potential xenotransplant to treat conditions like pancreatitis as the tissue source is abundantly available.

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Acinar cells are functional unit of pancreas.

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In vitro release of enzyme granules by exocytosis are well demonstrated.

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Amylase shares 86% protein identity with that of human.

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Acinar culture showed longer viability upto 20 days with normal cellular function.

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Useful culture model in understanding the acinar cell biology and physiology.

Apoptotic damage of pancreatic ductal epithelia by alcohol and its rescue by an antioxidant

Alcohol abuse is a major cause of pancreatitis. However alcohol toxicity has not been fully elucidated in the pancreas and little is known about the effect of alcohol on pancreatic ducts. We report the molecular mechanisms of ethanol-induced damage of pancreatic duct epithelial cells (PDEC). Ethanol treatment for 1, 4, and 24 h resulted in cell death in a dose-dependent manner. The ethanol-induced cell damage was mainly apoptosis due to generation of reactive oxygen species (ROS), depolarization of mitochondrial membrane potential (MMP), and activation of caspase-3 enzyme. The antioxidant N-acetylcysteine (NAC) attenuated these cellular responses and reduced cell death significantly, suggesting a critical role for ROS. Acetaldehyde, a metabolic product of alcohol dehydrogenase, induced significant cell death, depolarization of MMP, and caspase-3 activation as ethanol and this damage was also averted by NAC. Reverse transcription-polymerase chain reaction revealed the expression of several subtypes of alcohol dehydrogenase and acetaldehyde dehydrogenase. Nuclear magnetic resonance spectroscopy data confirmed the accumulation of acetaldehyde in ethanol-treated cells, suggesting that acetaldehyde formation can contribute to alcohol toxicity in PDEC. Finally, ethanol increased the leakage of PDEC monolayer which was again attenuated by NAC. In conclusion, ethanol induces apoptosis of PDEC and thereby may contribute to the development of alcohol-induced pancreatitis.