Dominant negative p38 mitogen-activated protein kinase expression inhibits NF-kappaB activation in AR42J cells

Identification of ceRNA regulatory network in acute pancreatitis and acute recurrent pancreatitis

OBJECTIVE

The aim of this study was to find differentially expressed long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and mRNAs and related signaling pathways, contributing to understanding the molecular mechanism of acute recurrent pancreatitis (ARP).

METHODS

First, peripheral whole blood samples from five acute pancreatitis (AP) patients, five ARP patients and five healthy individuals ( N ) were collected for RNA sequencing. Second, differentially/specifically expressed lncRNAs, miRNAs and mRNAs were identified in AP vs. N , ARP vs. N and ARP. Third, the ceRNA (lncRNA-miRNA-mRNA) networks of common/specifical lncRNAs, miRNAs and mRNAs were constructed in AP vs. N , ARP vs. N and ARP. Finally, functional analysis of common mRNAs in AP vs. N and ARP vs. N was performed.

RESULTS

A total of 315 common lncRNAs, 12 common miRNAs and 909 common mRNAs were identified between AP and ARP. Ninety-four specifically expressed lncRNAs, one specifically expressed miRNAs and 286 specifically expressed mRNAs were found in ARP. Some interaction pairs were identified in AP and ARP, such as LUCAT1/NEAT1-hsa-miR-16-2-3p-HK2, CHRM3-AS2-hsa-miR-122-5p/hsa-miR-145-3p-DBH/CACNA1C, CHRM3-AS2-hsa-miR-200a-3p-PDGFD, RBM26-AS1-hsa-miR-200b-3p-FHIT and LINC00891/KTN1-AS1-hsa-miR-143-3p-tyrosine kinase (TXK). ASAP1-IT2/DGCR9-hsa-miR-342-5p-ABCC5/MAP2K6 was the only one specific interaction pair identified in ARP. Four significantly enriched signaling pathways were identified in AP vs. N and ARP vs. N , including amino sugar and nucleotide sugar metabolism (involved NPL and HK2), MAPK signaling pathway (involved CACNA1C and PDGFD), metabolic pathways (involved DBH and FHIT) and leukocyte transendothelial migration (involved TXK).

CONCLUSION

The identified altered lncRNAs, miRNAs, mRNAs and related signaling pathways may be involved in the AP development and recurrence.

Liver injury associated with acute pancreatitis: The current status of clinical evaluation and involved mechanisms

Acute pancreatitis (AP) is a very common acute disease, and the mortality rate of severe AP (SAP) is between 15% and 35%. The main causes of death are multiple organ dysfunction syndrome and infections. The mortality rate of patients with SAP related to liver failure is as high as 83%, and approximately 5% of the SAP patients have fulminant liver failure. Liver function is closely related to the progression and prognosis of AP. In this review, we aim to elaborate on the clinical manifestations and mechanism of liver injury in patients with AP.

Inhibition of the p38 MAPK pathway attenuates renal injury in pregnant rats with acute necrotizing pancreatitis

The p38 mitogen-activated protein kinase (MAPK) pathway is an important intracellular signalling pathway that leads to increased expression of pro-inflammatory mediators. Our previous studies have shown that the p38 MAPK pathway was changed in the acute renal injury (ARI) in acute pancreatitis in late pregnancy (APIP), whereas the role of p38 MAPK in APIP-induced ARI has been poorly understood. The present study was undertaken to investigate the participation of the p38 MAPK signalling pathway and the protective effect of SB203580, an inhibitor of p38 MAPK in ARI in APIP. Twenty-four late-gestation SD rats were randomly assigned to four groups: the normal group (N), sham-operated group (SO), acute necrotizing pancreatitis (ANP) group, and p38 MAPK inhibitor (SB203580) treatment group (T). The results showed that serum amylase, lipase, urea, and creatinine levels of p38 inhibitor of T groups were markedly lower than the ANP groups. Additionally, the expression of phosphorylated p38 and myeloperoxidase (MPO), tumour necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, nuclear factor kappa-B (NF-κB), caspase-3, and terminal deoxynucleotidyl TUNEL-positive cells was markedly lower in the T group than in the ANP group. Our results suggest that SB203580 can inhibit renal injury by inhibiting the P38 MAPK signalling pathway and blocking the inflammatory responses in APIP.

Alleviation of acute pancreatitis-associated lung injury by inhibiting the p38 mitogen-activated protein kinase pathway in pulmonary microvascular endothelial cells

BACKGROUND

Previous reports have suggested that the p38 mitogen-activated protein kinase signaling pathway is involved in the development of severe acute pancreatitis (SAP)-related acute lung injury (ALI). Inhibition of p38 by SB203580 blocked the inflammatory responses in SAP-ALI. However, the precise mechanism associated with p38 is unclear, particularly in pulmonary microvascular endothelial cell (PMVEC) injury.

AIM

To determine its role in the tumor necrosis factor-alpha (TNF-α)-induced inflammation and apoptosis of PMVECs in vitro. We then conducted in vivo experiments to confirm the effect of SB203580-mediated p38 inhibition on SAP-ALI.

METHODS

In vitro, PMVEC were transfected with mitogen-activated protein kinase kinase 6 (Glu), which constitutively activates p38, and then stimulated with TNF-α. Flow cytometry and western blotting were performed to detect the cell apoptosis and inflammatory cytokine levels, respectively. In vivo, SAP-ALI was induced by 5% sodium taurocholate and three different doses of SB203580 (2.5, 5.0 or 10.0 mg/kg) were intraperitoneally injected prior to SAP induction. SAP-ALI was assessed by performing pulmonary histopathology assays, measuring myeloperoxidase activity, conducting arterial blood gas analyses and measuring TNF-α, interleukin (IL)-1β and IL-6 levels. Lung microvascular permeability was measured by determining bronchoalveolar lavage fluid protein concentration, Evans blue extravasation and ultrastructural changes in PMVECs. The apoptotic death of pulmonary cells was confirmed by performing a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling analysis and examining the Bcl2, Bax, Bim and cle-caspase3 levels. The proteins levels of P-p38, NFκB, IκB, P-signal transducer and activator of transcription-3, nuclear factor erythroid 2-related factor 2, HO-1 and Myd88 were detected in the lungs to further evaluate the potential mechanism underlying the protective effect of SB203580.

RESULTS

In vitro, mitogen-activated protein kinase (Glu) transfection resulted in higher apoptotic rates and cytokine (IL-1β and IL-6) levels in TNF-α-treated PMVECs. In vivo, SB2035080 attenuated lung histopathological injury, decreased inflammatory activity (TNF-α, IL-1β, IL-6 and myeloperoxidase) and preserved pulmonary function. Furthermore, SB203580 significantly reversed changes in the bronchoalveolar lavage fluid protein concentration, Evans blue accumulation, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cell numbers, apoptosis-related proteins (cle-caspase3, Bim and Bax) and endothelial microstructure. Moreover, SB203580 significantly reduced the pulmonary P-p38, NFκB, P-signal transducer and activator of transcription-3 and Myd88 levels but increased the IκB and HO-1 levels.

CONCLUSION

p38 inhibition may protect against SAP-ALI by alleviating inflammation and the apoptotic death of PMVECs.

Macrophage Migration Inhibitor Promoted the Intrahepatic Bile Duct Injury in Rats with Severe Acute Pancreatitis

BACKGROUND

Macrophage migration inhibitory factor (MIF) is involved in many acute and chronic inflammatory diseases. However, its role in intrahepatic bile duct (IBD) cell damage associated with severe acute pancreatitis (SAP) remains unclear.

AIMS

This study was aimed to identify the role of MIF and its underlying mechanisms in SAP complicated by IBD cell damage.

METHODS

Forty-eight specific-pathogen-free male Wistar rats were randomly divided into four groups (N = 12): a sham operation group (SO group) and three SAP model groups (SAP-3h, SAP-6h, and SAP-12h). Immunohistochemistry was used to detect the expression of MIF and P38 in IBD cells. MIF mRNA expression in IBD cells was observed using real-time fluorescent quantitative polymerase chain reaction (real-time PCR). In addition, Western blotting was performed to detect the protein expression of P38, phosphorylated P38 (P-P38), nuclear factor-κB (NF-κB p65), and tumor necrosis factor alpha (TNF-α). Enzyme-linked immunosorbent assays were used to analyze the levels of TNF-α, IL-1β, and IL-6 in the IBD of rats.

RESULTS

Compared with the SO group, the expression of MIF in the IBD was significantly upregulated both at mRNA and at protein levels in the SAP group. Besides, the protein expression levels of P38, P-P38, NF-κB, p65, TNF-α, IL-1β, and IL-6 in the IBD in rats were also significantly increased in the SAP group and the levels increased gradually as acute pancreatitis progressed (all P < 0.05).

CONCLUSIONS

MIF may promote the IBD injury and inflammatory reaction in SAP via activating the P38-MAPK and NF-κB signaling pathways.

Expression of Notch-1 and nuclear factor-κB signal pathway in myocardial cells of coronary heart disease rats

Expression changes of Notch-1 and nuclear factor-κB (NF-κB) in cardiomyocytes from coronary heart disease (CHD) rats were investigated. The CHD model established by high-fat diet in 48 clean SD rats was set as the observation group, and another 48 healthy rats routinely fed were the control group. Rats were sacrificed on the 1st, 3rd, 7th, and 14th days after successful modeling. The rat myocardial cells were harvested to examine the changes of Notch-1 and NF-κB using immunoblot (western blot analysis) and TUNEL assay. Cardiomyocyte apoptotic rate, by Pearson's correlation test was used to analyze the correlation between Notch-1 and NF-κB. With the prolongation of the course of CHD in rats, the expression levels of Notch-1 and NF-κB proteins gradually increased, and the expression in the observation group was significantly higher than that in the control group (P<0.01). On the seventh day, the expression levels of Notch-1 and NF-κB protein in the rats in the observation group showed significant difference from those on day 1 and day 3 (P<0.05), and they were significantly different on the 7th and 14th days (P<0.05). There was no correlation between the expression level of the two proteins with the age and sex of the rats. Pearson's correlation analysis showed that Notch-1 was positively correlated with NF-κB protein (r=0.745, P=0.005). The results of myocardial apoptosis test showed that with the prolongation of the CHD course in the rats of the observation group, the cardiomyocyte apoptosis rate did not differ from the control group. The expression of Notch-1 and NF-κB protein is increased in cardiomyocytes of CHD rats. Notch-1 and NF-κB participate in the occurrence and development of CHD.

Macrophage migration inhibitory factor antagonist (S,R)3‑(4‑hydroxyphenyl)‑4,5‑dihydro‑5‑isoxazole acetic acid methyl ester attenuates inflammation and lung injury in rats with acute pancreatitis in pregnancy

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine involved in many acute and chronic inflammatory diseases. However, its role in acute lung injury associated with acute pancreatitis in pregnancy (APIP) has not yet been elucidated. The present study was undertaken to clarify the effect and potential mechanism of MIF antagonist (S,R)3‑(4‑hydroxyphenyl)‑4,5‑dihydro‑5‑isoxazole acetic acid methyl ester (ISO‑1) in the development of acute lung injury in rats with APIP. Eighteen late‑gestation SD rats were randomly assigned to three groups: Sham operation (SO) group, APIP group, and ISO‑1 group. All the rats were sacrificed 6 h after modeling. The severity of pancreatitis was evaluated by serum amylase (AMY), lipase (LIPA), tumor necrosis factor (TNF)‑α, interleukin (IL)‑1β and IL‑6 and assessing the histopathological score. Lung injury was determined by performing histology and inflammatory cell infiltration investigations. Western blot analysis was used to detect the protein expression of MIF, phosphorylated and total P38 and nuclear factor‑κB (NF‑κB) protein in lungs. The results showed that MIF was upregulated in the lung of APIP rats. Compared with APIP group, the intervention of ISO‑1 alleviated the pathological injury of the pancreas and lungs, decreased serum AMY and LIPA, attenuated serum concentrations of TNF‑α, IL‑1β, and IL‑6, reduced the number of MPO‑positive cells in the lung and inhibited the activation of P38MAPK and NF‑κB. These results suggest that MIF is activated in lung injury induced by APIP. Furhtermore, the present findings indicate that the MIF antagonist ISO‑1 has a protective effect on lung injury and inflammation, which may be associated with deactivating the P38MAPK and NF‑κB signaling pathway.

Involvement of the PI3K/Akt/NF-κB Signaling Pathway in the Attenuation of Severe Acute Pancreatitis-Associated Acute Lung Injury by Sedum sarmentosum Bunge Extract

Sedum sarmentosum Bunge possesses excellent anti-inflammatory properties and was used in the treatment of inflammatory diseases. The aim of the present study was to investigate the efficiency of Sedum sarmentosum Bunge extract (SSBE) on severe acute pancreatitis-associated (SAP-associated) acute lung injury (ALI) in rats and to explore the underlying mechanisms. Here, we used a sodium taurocholate-induced SAP rat model to determine the role of SSBE in ALI. During the course of pancreatitis, the expressions of phosphorylated phosphoinositide 3-kinases (PI3K)/protein kinase B (Akt) and nuclear factor-kappa B (NF-κB) p65 in the lungs were upregulated. Meanwhile, a parallel increase in the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the lungs was observed after the induction of SAP. Treatment with SSBE significantly reduced the expression of p-Akt and p-p65 in the lungs and attenuated the severity of SAP-associated ALI compared to the SAP group at 12 h and 24 h. In summary, this study showed that SSBE has beneficial effects on SAP-associated ALI, probably through the PI3-K/Akt signaling pathways by suppressing the NF-κB activities.

Angiotensin-converting enzyme 2-angiotensin (1-7)-Mas axis prevents pancreatic acinar cell inflammatory response via inhibition of the p38 mitogen-activated protein kinase/nuclear factor-κB pathway

The aim of the present study was to investigate the role of the angiotensin-converting enzyme (ACE)2-angiotensin‑(Ang)-(1-7)-Mas axis in the pathogenesis of pancreatitis and the association between this axis and the p38 mitogen-activated protein kinase (p38 MAPK)/nuclear factor (NF-κB) signaling pathway in pancreatic acinar cells. Mouse pancreatic acinar cancer (MPC-83) cells were stimulated with 10 nM caerulein (CAE) to create an in vitro model of acute pancreatitis, and collected for analysis at 2, 6, 12, 24 and 48 h post stimulation. In addition, cells were pretreated with different concentrations of Ang‑(1‑7), Ang‑(1‑7) antagonist A779, p38 MAPK inhibitor SB203580 or ACE2 inhibitor DX600 for 30 min, and then stimulated with CAE for 24 h. The ACE2, Mas receptor, p38 MAPK, phosphorylated (p)-p38 MAPK and NF-κB expression levels were evaluated using western blotting and immunofluorescence. p38 MAPK, NF-κB, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-8 and IL-10 mRNA expression levels were assessed using reverse transcription-quantitative polymerase chain reaction. The results of the immunofluorescence assay demonstrated that ACE2 and p38 MAPK were present mainly in the cytoplasm, while the Mas receptor was located mainly in the cell membrane. ACE2, p38 MAPK and p-p38 MAPK protein levels were significantly increased (P<0.05) following stimulation with CAE compared with those in the control group and peaked at 24 h. Mas receptor protein levels were significantly upregulated (P<0.05) between 6 and 24 h, peaking at 12 h. Ang‑(1‑7) and SB203580 downregulated p-p38 MAPK and NF-κB expression and the mRNA levels of inflammatory factors IL-6, TNF-α and IL-8, but upregulated the mRNA level of inflammatory factor IL-10 compared with those treated with CAE alone. These results were supported by the opposite outcomes observed for cells treated with A779 or DX600. Therefore, it was concluded that the ACE2-Ang‑(1‑7)-Mas axis significantly inhibits pancreatitis by inhibition of the p38 MAPK/NF-κB signaling pathway.

Deciphering fact from artifact when using reporter assays to investigate the roles of host factors on L1 retrotransposition

BACKGROUND

The Long INterspersed Element-1 (L1, LINE-1) is the only autonomous mobile DNA element in humans and has generated as much as half of the genome. Due to increasing clinical interest in the roles of L1 in cancer, embryogenesis and neuronal development, it has become a priority to understand L1-host interactions and identify host factors required for its activity. Apropos to this, we recently reported that L1 retrotransposition in HeLa cells requires phosphorylation of the L1 protein ORF1p at motifs targeted by host cell proline-directed protein kinases (PDPKs), which include the family of mitogen-activated protein kinases (MAPKs). Using two engineered L1 reporter assays, we continued our investigation into the roles of MAPKs in L1 activity.

RESULTS

We found that the MAPK p38δ phosphorylated ORF1p on three of its four PDPK motifs required for L1 activity. In addition, we found that a constitutively active p38δ mutant appeared to promote L1 retrotransposition in HeLa cells. However, despite the consistency of these findings with our earlier work, we identified some technical concerns regarding the experimental methodology. Specifically, we found that exogenous expression of p38δ appeared to affect at least one heterologous promoter in an engineered L1 reporter, as well as generate opposing effects on two different reporters. We also show that two commercially available non-targeting control (NTC) siRNAs elicit drastically different effects on the apparent retrotransposition reported by both L1 assays, which raises concerns about the use of NTCs as normalizing controls.

CONCLUSIONS

Engineered L1 reporter assays have been invaluable for determining the functions and critical residues of L1 open reading frames, as well as elucidating many aspects of L1 replication. However, our results suggest that caution is required when interpreting data obtained from L1 reporters used in conjunction with exogenous gene expression or siRNA.

Pancreatic Acinar Cells Employ miRNAs as Mediators of Intercellular Communication to Participate in the Regulation of Pancreatitis-Associated Macrophage Activation

Macrophage activation plays an important role in the inflammatory response in acute pancreatitis. In the present study, the activation of AR42J pancreatic acinar cells was induced by taurolithocholate treatment. The results showed that the culture medium from the activated AR42J cells significantly enhanced NFκB activation in the macrophages compared to that without taurolithocholate treatment. Additionally, the precipitates obtained from ultracentrifugation of the culture media that were rich in exosomes were markedly more potent in activating macrophages compared with the supernatant fraction lacking exosomes. The results indicated that the mediators carried by the exosomes played important roles in macrophage activation. Exosomal miRNAs were extracted and examined using microarrays. A total of 115 differentially expressed miRNAs were identified, and 30 showed upregulated expression, while 85 displayed downregulated expression. Target genes of the differentially expressed miRNAs were predicted using TargetScan, MiRanda, and PicTar software programs. The putative target genes were subjected to KEGG functional analysis. The functions of the target genes were primarily enriched in MAPK pathways. Specifically, the target genes regulated macrophage activation through the TRAF6-TAB2-TAK1-NIK/IKK-NFκB pathway. As the mediators of signal transduction, miRNAs and their predicted target mRNAs regulate every step in the MAPK pathway.

miR-29a up-regulation in AR42J cells contributes to apoptosis via targeting TNFRSF1A gene

AIM: To investigate the expression of miR-29a in rat acute pancreatitis and its functional role in AR42J cell apoptosis.

METHODS: Twelve SD rats were divided into a control group and an acute edematous pancreatitis (AEP) group randomly. AEP was induced by intraperitoneal injection of L-arginine (150 mg/kg) in the AEP group and equal volume of 0.9% NaCl was injected in the control group. The apoptosis of acinar cells in pancreatic tissue was determined by TUNEL assay. miRNA chip assay was performed to examine the expression of miRNAs in two groups. Besides, to further explore the role of miR-29a in apoptosis in vitro, recombinant rat TNF-α (50 ng/mL) was administered to treat the rat pancreatic acinar cell line AR42J for inducing AR42J cell apoptosis. Quantitative real-time PCR (qRT-PCR) was adopted to measure miR-29a expression. Then, miRNA mimic, miRNA antisense oligonucleotide (AMO) and control vector were used to transfect AR42J cells. The expression of miR-29a was confirmed by qRT-PCR and the apoptosis rate of AR42J cells was detected by flow cytometry analysis. Western blot was used to detect the expression of activated caspase3. Moreover, we used bioinformatics software and luciferase assay to test whether TNFRSF1A was the target gene of miR-29a. After transfection, qRT-PCR and Western blot was used to detect the expression of TNFRSF1A in AR42J cells after transfection.

RESULTS: The expression of miR-29a was much higher in the AEP group compared with the control group as displayed by the miRNA chip assay. After inducing apoptosis of AR42J cells in vitro, the expression of miR-29a was significantly increased by 1.49 ± 0.04 times in comparison with the control group. As revealed by qRT-PCR assay, the expression of miR-29a was 2.68 ± 0.56 times higher in the miR-29a mimic group relative to the control vector group, accompanied with an obviously increased acinar cell apoptosis rate (42.83 ± 1.25 vs 24.97 ± 0.15, P < 0.05). Moreover, the expression of miR-29a in the miRNA AMO group was 0.46 ± 0.05 times lower than the control vector group, and the cell apoptosis rate was much lower accordingly (17.27 ± 1.36 vs 24.97 ± 0.15, P < 0.05). The results of bioinformatics software and luciferase assay showed that TNFRSF1A might be a target gene of miR-29a. TNFRSF1A expression was up-regulated in the miR-29a mimic group, while the miR-29a AMO group showed the reverse trend.

CONCLUSION: miR-29a might promote the apoptosis of AR42J cells via up-regulating the expression of its target gene TNFRSF1A.

MAPKs and Hsc70 are critical to the protective effect of molecular hydrogen during the early phase of acute pancreatitis

Molecular hydrogen (H2 ) has been proven to be an effective agent that can cure multiple organ diseases by reducing oxidative stress. Although the protective effect of hydrogen on acute pancreatitis (AP) has been confirmed, its molecular mechanism is still unclear. In this article, we aimed to investigate the changes in pancreatic cell protein expression associated with the protective effect of H2 against AP and attempted to uncover the molecular mechanism underlying this process. A proteomic analysis identified 73 differentially expressed proteins and generated the protein-protein interaction networks of these proteins. The results triggered our interest in mitogen-activated protein kinase (MAPK) and heat shock cognate 71 kDa protein (Hsc70). The subsequent in vitro experiments showed that H2 treatment inhibited the phosphorylation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK), and p38 MAPK, and activated NF-κB and the expression of tumor necrosis factor α and interleukin-1β, while simultaneously preventing the translocation of phospho-ERK, phospho-JNK, and phospho-p38 from the cytoplasm to the nucleus. Furthermore, Hsc70 expression was upregulated by H2 administration. The animal experimental results were consistent with those of the in vitro experiments. In conclusion, H2 treatment can ameliorate the inflammatory response and reduce the expression of inflammatory mediators during the early phase of AP by inhibiting the MAPK pathways and increasing Hsc70 expression.

An expandable donor-free supply of functional hepatocytes for toxicology

The B-13 cell is a readily expandable rat pancreatic acinar-like cell that differentiates on simple plastic culture substrata into replicatively-senescent hepatocyte-like (B-13/H) cells in response to glucocorticoid exposure. B-13/H cells express a variety of liver-enriched and liver-specific genes, many at levels similar to hepatocytes in vivo. Furthermore, the B-13/H phenotype is maintained for at least several weeks in vitro, in contrast to normal hepatocytes which rapidly de-differentiate under the same simple – or even under more complex – culture conditions. The origin of the B-13 cell line and the current state of knowledge regarding differentiation to B-13/H cells are presented, followed by a review of recent advances in the use of B-13/H cells in a variety of toxicity endpoints. B-13 cells therefore offer Toxicologists a cost-effective and easy to use system to study a range of toxicologically-related questions. Dissecting the mechanism(s) regulating the formation of B-13/H cell may also increase the likelihood of engineering a human equivalent, providing Toxicologists with an expandable donor-free supply of functional rat and human hepatocytes, invaluable additions to the tool kit of in vitro toxicity tests.

Evidence for a role of mitogen-activated protein kinases in the treatment of experimental acute pancreatitis

Acute pancreatitis (AP) is an inflammatory disease characterized by acute inflammation and necrosis of the pancreatic parenchyma. AP is often associated with organ failure, sepsis, and high mortality. The pathogenesis of AP is still not well understood. In recent years several papers have highlighted the cellular and molecular events of acute pancreatitis. Pancreatitis is initiated by activation of digestive enzymes within the acinar cells that are involved in autodigestion of the gland, followed by a massive infiltration of neutrophils and macrophages and release of inflammatory mediators, responsible for the local and systemic inflammatory response. The hallmark of AP is parenchymal cell necrosis that represents the cause of the high morbidity and mortality, so that new potential therapeutic approaches are indispensable for the treatment of patients at high risk of complications. However, not all factors that determine the onset and course of the disease have been explained. Aim of this article is to review the role of mitogen-activated protein kinases in pathogenesis of acute pancreatitis.

Regulation of pancreatic inflammation by connective tissue growth factor (CTGF/CCN2)

Pancreatitis is caused by long-term heavy alcohol consumption, which results in injury and death of pancreatic acinar cells (PAC). The PAC play a pivotal role in mediating early inflammatory responses but the underlying mechanisms remain poorly understood. Treatment of C57BL/6 mice with ethanol and cerulein resulted in increased staining for acinar interleukin- 1b (IL-1b), chemokine (C-C motif) ligand 3 (CCL3), or connective tissue growth factor (CTGF/CCN2) by Day 16 and this was associated with increased infiltration of F4/80-positive macrophages and increased expression of pancreatic CTGF/CCN2 mRNA. Compared with wild-type Swiss Webster mice, ethanol treatment of pan-green fluorescent protein (GFP)-CTGF/CCN2 transgenic mice caused enhanced acinar staining for GFP or CTGF/CCN2 and a significant increase in pancreatic infiltration of F4/80-positive macrophages or NIMP-R14-positive neutrophils. Treatment of primary mouse PAC or the rat AR42J PAC line with ethanol or CTGF/CCN2 resulted in enhanced expression of IL-1b or CCL3. Conditioned medium from CTGF/CCN2-treated AR42J cells induced chemotaxis in NR8383 macrophages and this response was abrogated in a dose dependent manner by addition of BX471, an inhibitor of chemokine (C-C motif) receptor 1. These results reveal that acinar CTGF/CCN2 plays a novel role in alcohol-induced inflammatory processes in the pancreas by increasing infiltration of macrophages and neutrophils and increasing acinar production of inflammatory mediators such as IL-1b or CCL3. The early production of CTGF/CCN2 by PAC to drive inflammation is distinct from its previously reported production by pancreatic stellate cells to drive fibrosis at later stages of pancreatic injury.

Effect of emodin on endoplasmic reticulum stress in rats with severe acute pancreatitis

This study aimed to investigate the protective effect of emodin on endoplasmic reticulum (ER) stress in rats with severe acute pancreatitis (SAP) and the underlying molecular mechanism. Sprague-Dawley male rats were randomly divided into sham operation group, SAP model group, and emodin treatment group. SAP was constructed through injecting sodium taurocholate into pancreatic and biliary duct in rats. Half an hour before establishing the animal model, emodin or sodium carboxymethylcellulose was intragastrically administrated to the rats in respective group. Rats were killed at 3, 6, and 12 h postdisease induction. The amylase, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) levels in serum, pancreatic histopathology, acinar ER ultrastructure, protein expression of Bip, IRE1α,TRAF2, ASK1, p-JNK, and p-p38 MAPK in pancreas were examined. Sodium taurocholate induced pancreatic injury and ER lumen dilated in exocrine pancreas in rats at 3-, 6-, and 12-h time points. ER stress transducers Bip, IRE1α, and their downstream molecules TRAF2, ASK1 in pancreatitis were upregulated. Furthermore, phosphorylation of JNK and p38MAPK in pancreas was increased, which induced high expression level of inflammatory cytokines such as TNF-α and IL-6. Treatment with emodin obviously ameliorated pancreatic injury and decreased the release of amylase and inflammatory cytokines. Further studies showed that emodin significantly decreased the expression of Bip, IRE1α, TRAF2, and ASK1, inhibited phosphorylation of JNK and p38 MAPK in pancreas in rats at all time points. Emodin could reduce pancreatic injury and restrain inflammatory reaction in SAP rats partly via inhibiting ER stress transducers IRE1α and its downstream molecules.

Expressions of miR-22 and miR-135a in acute pancreatitis

This study examined the expressions of miR-22 and miR-135a in rats with acute edematous pancreatitis (AEP) and their target genes in order to shed light on the involvement of miR-22 and miR-135a in the pathogenesis of acute pancreatitis (AP). The in vivo model of AEP was established by introperitoneal injection of L-arginine (150 mg/kg) in rats. The miRNA microarray analysis was used to detect the differential expression of miRNAs in pancreatic tissue in AEP and normal rats. The in vitro AEP model was established by inducing the rat pancreatic acinar cell line (AR42J) with 50 ng/mL recombinant rat TNF-α. Real-time quantitative RT-PCR was employed to detect the expression of miR-22 and miR-135a in AR42J cells. Lentiviruses carrying the miRNA mimic and anti-miRNA oligonucleotide (AMO) of miR-22 and miR-135a were transfected into the AR42J cells. The AR42J cells transfected with vehicle served as control. Western blotting was used to measure the expression of activated caspase3 and flow cytometry analysis to detect the apoptosis of AR42J cells. Targets of miR-22 and miR-135a were predicted by using TargetScan, miRanda, and TarBase. Luciferase reporter assay and quantitative real-time RT-PCR were performed to confirm whether ErbB3 and Ptk2 were the target gene of miR-22 and miR-135a, respectively. The results showed that the expression levels of miR-22 and miR-135a were obviously increased in AEP group compared with the control group in in-vivo and in-vitro models. The expression levels of miR-22 and miR-135a were elevated conspicuously and the expression levels of their target genes were reduced significantly in AR42J cells transfected with lentiviruses carrying the miRNA mimic. The apoptosis rate was much higher in the TNF-α-induced cells than in non-treated cells. The AR42J cells transfected with miRNA AMOs expressed lower level of miR-22 and miR-135a and had lower apoptosis rate, but the expression levels of ErbB3 and Ptk2 were increased obviously. It was concluded that the expression levels of miR-22 and miR-135a were elevated in AEP. Up-regulating the expression of miR-22 and miR-135a may promote the apoptosis of pancreatic acinar cells by repressing ErbB3 and Ptk2 expression in AEP.

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.

Taurine attenuates liver injury by downregulating phosphorylated p38 MAPK of Kupffer cells in rats with severe acute pancreatitis

This study was undertaken to clarify the effects of taurine on liver injury in rats with severe acute pancreatitis (SAP). Rats were randomly assigned to three groups: a sham operation (SO), a SAP (established by infusion of 5% taurocholate), and a SAP given taurine (Taur). At 12 and 24 h post-operation, taurine pretreatment significantly attenuated hepatic tissue injury induced by SAP, and concurrently, serum alanine aminotransferase, aspartate transaminase, and amylase levels were significantly reduced by taurine pretreatment. Compared with the SO group, the total and phosphorylated p38 mitogen-activated protein kinase (p38 MAPK) expression and nuclear factor-κB (NF-κB) activity of Kupffer cells (KCs) were significantly higher in the SAP group, but taurine pretreatment inhibited the total and phosphorylated p38 MAPK expression and NF-κB activity of KCs in the SAP group. The increase of tumor necrosis factor-α and interleukin-lβ in cultured supernate of the SAP rat-derived KCs was also significantly inhibited by taurine pretreatment. These results suggest that taurine pretreatment ameliorated liver injury in rats with SAP mainly by inhibiting phosphorylated p38 MAPK and NF-κB activity in KCs, which may play an important role in liver injury.

Emodin protects from deoxycholic acid-induced AR42J cell damage

AIM: To investigate whether emodin exerts a protect effect against deoxycholic acid (DCA)-induced cell damage in rat pancreatic acinar cell line AR42J.

METHODS: AR42J cells were divided into five groups: normal control cells, cells treated with 0.4 or 0.8 mmol/L DCA, and those treated with 0.4 or 0.8 mmol/L DCA plus emodin (20 mg/L). The rates of apoptosis and necrosis were detected by flow cytometry and AV/PI double staining. The activity of amylase in the medium and cytoplasm was determined.

RESULTS: DCA at a dose of 0.4 mmol/L mainly induced the apoptosis of AR42J cells, while 0.8 mmol/L of DCA induced the necrosis of AR42J cells. Emodin significantly reduced DCA-induced late apoptosis (27.9% vs 34.1%) and necrosis (38.1% vs 45.4%), but did not significantly change the activity of amylase in the medium and cytoplasm of AR42J cells.

CONCLUSION: Emodin has some protective effects against DCA-induced AR42J cell damage, but does not influence amylase synthesis and secretion by acinar cells.

Systemic inflammation with multiorgan dysfunction is the cause of death in murine ligation-induced acute pancreatitis

BACKGROUND

We have previously shown that distal pancreatic duct ligation-induced acute pancreatitis in mice is associated with substantial mortality.

METHODS

We examined the cause of death in duct ligation-induced acute pancreatitis in mice by serial examination of multiple parameters in three experimental groups: distal pancreatic duct ligation (PD), bile duct ligation alone (BD), and sham operation (S).

RESULTS

BD and S had no mortality, while PD had 94% mortality with most deaths between days 2 and 4. Characteristics of mice with acute pancreatitis included (ANOVA; p < 0.05): extracellular regulated kinase activation in the pancreas and lung; pancreatic neutrophil infiltration and acinar cell necrosis maximal on day 2; increased plasma cytokine and aspartate aminotransferase levels and bronchoalveolar lavage fluid neutrophil count and cytokine levels, peaked on day 3; hypotension and bradycardia were worst on day 4; pulmonary neutrophil infiltration and plasma creatinine level peaked on day 4. Liver injury evidenced by raised aspartate serum transaminase after hepatic obstruction was exacerbated by PD.

CONCLUSIONS

Systemic inflammation with multiorgan dysfunction causes death in pancreatic duct ligation-induced acute pancreatitis in mice. This experimental model is a suitable experimental analogy of "early severe gallstone pancreatitis" to investigate disease pathogenesis and to evaluate novel therapeutic strategies.

Molecular mechanisms of pancreatic injury

PURPOSE OF REVIEW

Despite being a subject of much scientific scrutiny, the pathogenesis of acute pancreatitis is still not well understood. This article reviews recent advances in our understanding of acute pancreatitis.

RECENT FINDINGS

Zymogen activation, observed within acini early during acute pancreatitis for a long time, was shown to be sufficient to induce acute pancreatitis. Another key early event, NFκB activation, has previously been shown to induce acute pancreatitis. The relationship between these two key early steps is beginning to be clarified. Mechanisms of zymogen activation - pathologic calcium signaling, pH changes, colocalization and autophagy, and of NFκB activation have been investigated intensively along with potential therapeutic targets both upstream and downstream of these key events. Additional key findings have been elucidation of the role of bioenergetics and the dual role of oxidative stress in acute pancreatitis, recognition of endoplasmic reticulum stress as an early step and the status of duct cells as important entities in pancreatic injury.

SUMMARY

Current findings have provided further insight into the roles and mechanisms of zymogen activation and inflammatory pathways in pancreatic injury. Future studies, which will be of great importance in identifying therapeutic targets, are being undertaken to establish the relative contributions of these pathways during acute pancreatitis.

A novel model of severe gallstone pancreatitis: murine pancreatic duct ligation results in systemic inflammation and substantial mortality

BACKGROUND

Suitable experimental models of gallstone pancreatitis with systemic inflammation and mortality are limited. We developed a novel murine model of duct-ligation-induced acute pancreatitis associated with multiorgan dysfunction and severe mortality.

METHODS

Laparotomy was done on C57/BL6 mice followed by pancreatic duct (PD) ligation, bile duct (BD) ligation without PD ligation, or sham operation.

RESULTS

Only mice with PD ligation developed acute pancreatitis and had 100% mortality. Pulmonary compliance was significantly reduced after PD ligation but not BD ligation. Bronchoalveolar lavage fluid neutrophil count and interleukin-1β concentration, and the plasma creatinine level, were significantly elevated with PD ligation but not BD ligation. Pancreatic nuclear factor κB (p65) and activator protein 1 (c-Jun) were activated within 1 h of PD ligation.

CONCLUSION

PD-ligation-induced acute pancreatitis in mice is associated with systemic inflammation, acute lung injury, multiorgan dysfunction and death. The development of this novel model is an exciting and notable advance in the field.