Gene expression profiling and endothelin in acute experimental pancreatitis

Irreversible and sustained upregulation of endothelin axis during oncogene-associated pancreatic inflammation and cancer

Endothelin-1 (ET-1) and its two receptors, endothelin receptor A (ETAR) and endothelin receptor B (ETBR) exhibit deregulated overexprerssion in pancreatic ductal adenocarcinoma (PDAC) and pancreatitis. We examined the expression pattern of endothelin (ET) axis components in the murine models of chronic and acute inflammation in the presence or absence of oncogenic K-ras. While the expression of endothelin converting enzyme-1 (ECE-1), ET-1, ETAR and ETBR in the normal pancreas is restricted predominantly to the islet cells, progressive increase of ET receptors in ductal cells and stromal compartment is observed in the KC model (Pdx-1 Cre; K-rasG12D) of PDAC. In the murine pancreas harboring K-rasG12D mutation (KC mice), following acute inflammation induced by cerulein, increased ETAR and ETBR expression is observed in the amylase and CK19 double positive cells that represent cells undergoing pancreatic acinar to ductal metaplasia (ADM). As compared to the wild type (WT) mice, cerulein treatment in KC mice resulted in significantly higher levels of ECE-1, ET-1, ETAR and ETBR, transcripts in the pancreas. Similarly, in response to cigarette smoke-induced chronic inflammation, the expression of ET axis components is significantly upregulated in the pancreas of KC mice as compared to the WT mice. In addition to the expression in the precursor pancreatic intraepithelial neoplasm (PanIN lesions) in cigarette smoke-exposure model and metaplastic ducts in cerulein-treatment model, ETAR and ETBR expression is also observed in infiltrating F4/80 positive macrophages and α-SMA positive fibroblasts and high co-localization was seen in the presence of oncogenic K-ras. In conclusion, both chronic and acute pancreatic inflammation in the presence of oncogenic K-ras contribute to sustained upregulation of ET axis components in the ductal and stromal cells suggesting a potential role of ET axis in the initiation and progression of PDAC.

Endogenous H2S sensitizes PAR4-induced bladder pain

Bladder pain is a prominent symptom of interstitial cystitis/painful bladder syndrome. Hydrogen sulfide (H₂S) generated by cystathionine β-synthase (CBS) or cystathionine γ-lyase (CSE) facilitates bladder hypersensitivity. We assessed involvement of the H₂S pathway in protease-activated receptor 4 (PAR4)-induced bladder pain. A bladder pain model was induced by intravesical instillation of PAR4-activating peptide in mice. The role of H₂S in this model was evaluated by intraperitoneal preadministration of d,l-propargylglycine (PAG), aminooxyacetic acid (AOAA), or S-adenosylmethionine or the preintravesical administration of NaHS. SV-HUC-1 cells were treated in similar manners. Assessments of CBS, CSE, and macrophage migration inhibitory factor (MIF) expression, bladder voiding function, bladder inflammation, H₂S production, and referred bladder pain were performed. The CSE and CBS pathways existed in both mouse bladders and SV-HUC-1 cells. H₂S signaling was upregulated in PAR4-induced bladder pain models, and H₂S-generating enzyme activity was upregulated in human bladders, mouse bladders, and SV-HUC-1 cells. Pretreatment with AOAA or NaHS inhibited or promoted PAR4-induced mechanical hyperalgesia, respectively; however, PAG only partially inhibited PAR4-induced bladder pain. Treatment with PAG or AOAA decreased H₂S production in both mouse bladders and SV-HUC-1 cells. Pretreatment with AOAA increased MIF protein levels in bladder tissues and cells, whereas pretreatment with NaHS lowered MIF protein levels. Bladder pain triggered by the H₂S pathway was not accompanied by inflammation or altered micturition behavior. Thus endogenous H₂S generated by CBS or CSE caused referred hyperalgesia mediated through MIF in mice with PAR4-induced bladder pain, without causing bladder injury or altering micturition behavior.

Multiorgan chronic inflammatory hepatobiliary pancreatic murine model deficient in tumor necrosis factor receptors 1 and 2

AIM: To provoke persistent/chronic multiorgan inflammatory response and to contribute to stones formation followed by fibrosis in hepatobiliary and pancreatic tissues.

METHODS: Tumor necrosis factor receptors 1 and 2 (TNFR1/R2) deficient mice reared in-house were given dibutyltin dichloride (DBTC) twice within 10 d by oral gavage delivery. Sham control animals received vehicle treatment and naïve animals remained untreated throughout the study. Animals were monitored daily for symptoms of pain and discomfort. The abdominal and hindpaw hypersensitivity were assessed with von Frey microfilaments. Exploratory behaviors were recorded at the baseline, after initiation of treatment, and before study termination. Histopathological changes were examined postmortem in tissues. Collagen accumulation and fibrosis were confirmed with Sirius Red staining.

RESULTS: Animals lost weight after oral administration of DBTC and developed persistent inflammatory abdominal and hindpaw hypersensitivity compared to sham-treated controls (P < 0.0001). These pain related secondary mechanical hypersensitivity responses increased more than 2-fold in DBTC-treated animals. The drastically diminished rearing and grooming rates persisted after DBTC administration throughout the study. Gross as well as micropathology at one month confirmed that animals treated with DBTC developed chronic hepatobiliary injuries evidenced with activation of stellate cells, multifocal necrosis, fatty degeneration of hepatocytes, periportal infiltration of inflammatory cells, and prominent biliary ductal dilation. The severity of hepatitis was scored 3.7 ± 0.2 (severe) in DBTC-treated animals vs score 0 (normal) in sham-treated animals. Fibrotic thickening was extensive around portal ducts, in hepatic parenchyma as well as in lobular pancreatic structures and confirmed with Sirius Red histopathology. In addition, pancreatic microarchitecture was presented with distortion of islets, and parenchyma, infiltration of inflammatory cells, degeneration, vacuolization, and necrosis of acinar cells and distention of pancreatic ducts. Extent of pancreatic damage and pancreatitis were scored 3.6 ± 0.4 (severe) for DBTC-treated in contrast to score 0 (normal) in sham-treated animals. The gall bladder became expanded with ductal distention, and occasional bile stones were detected along with microscopic hepatic lesions. DBTC-treated animals developed splenic hypertrophy with increased weight and length (P < 0.01) along with thymic atrophy (P < 0.001). Finally, colitic lesions and colitis were prominent in DBTC-treated animals and scored 3.4 ± 0.3 (moderately severe) vs 0 (normal) for the sham-treated animals.

CONCLUSION: This is the first report of chronic inflammatory multiorgan hepatobiliary pancreatitis, along with fibrosis and calculi formation induced reliably utilizing oral DBTC administration in TNFR1/R2 deficient mice.

P38 pathway regulates iNOS and PGE2 expression in hippocampal neurons in rats with severe acute pancreatitis

AIM: To investigate the effect of P38 mitogen-activated protein kinase (P38MAPK) pathway on the expression of inducible nitric oxide synthase (iNOS) and prostaglandin E2 (PGE2) in hippocampal neurons of rats with severe acute pancreatitis (SAP).

METHODS: Healthy male Sprague-Dawley rats were randomly divided into three groups: a control group, a model group, and an SB203580 (an inhibitor of P38MAPK pathway) group. The pathological changes in brain tissue were observed. By immunohistochemistry and Western blot, expression of iNOS and PGE2 and phosphorylation of P38MAPK were detected to observe the changes of positive cell numbers and the expression levels in the hippocampus.

RESULTS: Compared with the control group, the numbers of p-P38 (20.4 ± 2.2 vs 2.1 ± 1.3), iNOS (33.6 ± 4.4 vs 3.7 ± 0.4), and PGE2 (34.7 ± 4.0 vs 2.4 ± 1.0) immunoreactive cells increased markedly in the hippocampal CA1 region (P < 0.05). After treatment with SB203580, the numbers of p-P38 (12.8 ± 0.7), iNOS (14.4 ± 4.9), and PGE2 (18.3 ± 0.5) immunoreactive cells were reduced significantly as compared with the model group (P < 0.05). The inhibitor group had significantly improved pancreatic cell pathology compared to the SAP group, which had ultrastructural changes such as rough endoplasmic network degranulation and mitochondrial swelling expansion.

CONCLUSION: P38MAPK pathway regulates the expression of iNOS and PGE2 in the hippocampus, and inhibition of the pathway has a neuroprotective effect in rats with SAP.

Animal models of gastrointestinal and liver diseases. Animal models of visceral pain: pathophysiology, translational relevance, and challenges

Visceral pain describes pain emanating from the thoracic, pelvic, or abdominal organs. In contrast to somatic pain, visceral pain is generally vague, poorly localized, and characterized by hypersensitivity to a stimulus such as organ distension. Animal models have played a pivotal role in our understanding of the mechanisms underlying the pathophysiology of visceral pain. This review focuses on animal models of visceral pain and their translational relevance. In addition, the challenges of using animal models to develop novel therapeutic approaches to treat visceral pain will be discussed.

Macrophage Migration Inhibitory Factor Mediates PAR-Induced Bladder Pain

Introduction

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, is constitutively expressed in urothelial cells that also express protease-activated receptors (PAR). Urothelial PAR1 receptors were shown to mediate bladder inflammation. We showed that PAR1 and PAR4 activator, thrombin, also mediates urothelial MIF release. We hypothesized that stimulation of urothelial PAR1 or PAR4 receptors elicits release of urothelial MIF that acts on MIF receptors in the urothelium to mediate bladder inflammation and pain. Thus, we examined the effect of activation of specific bladder PAR receptors on MIF release, bladder pain, micturition and histological changes.

Methods

MIF release was measured in vitro after exposing immortalized human urothelial cells (UROtsa) to PAR1 or PAR4 activating peptides (AP). Female C57BL/6 mice received intravesical PAR1- or PAR4-AP for one hour to determine: 1) bladder MIF release in vivo within one hour; 2) abdominal hypersensitivity (allodynia) to von Frey filament stimulation 24 hours after treatment; 3) micturition parameters 24 hours after treatment; 4) histological changes in the bladder as a result of treatment; 5) changes in expression of bladder MIF and MIF receptors using real-time RT-PCR; 6) changes in urothelial MIF and MIF receptor, CXCR4, protein levels using quantitative immunofluorescence; 7) effect of MIF or CXCR4 antagonism.

Results

PAR1- or PAR4-AP triggered MIF release from both human urothelial cells in vitro and mouse urothelium in vivo. Twenty-four hours after intravesical PAR1- or PAR4-AP, we observed abdominal hypersensitivity in mice without changes in micturition or bladder histology. PAR4-AP was more effective and also increased expression of bladder MIF and urothelium MIF receptor, CXCR4. Bladder CXCR4 localized to the urothelium. Antagonizing MIF with ISO-1 eliminated PAR4- and reduced PAR1-induced hypersensitivity, while antagonizing CXCR4 with AMD3100 only partially prevented PAR4-induced hypersensitivity.

Conclusions

Bladder PAR activation elicits urothelial MIF release and urothelial MIF receptor signaling at least partly through CXCR4 to result in abdominal hypersensitivity without overt bladder inflammation. PAR-induced bladder pain may represent an interesting pre-clinical model of Interstitial Cystitis/Painful Bladder Syndrome (IC/PBS) where pain occurs without apparent bladder injury or pathology. MIF is potentially a novel therapeutic target for bladder pain in IC/PBS patients.

Application of caerulein and lipopolysaccharides in creating mouse models of mild or severe acute pancreatitis

AIM: To establish typical mouse models of mild or severe acute pancreatitis induced with caerulein (CAE) and/or lipopolysaccharides (LPS).

METHODS: Fifty healthy adult male C57 mice were randomly divided into five groups (with 10 mice in each group): a control group (CON group), the caerulein 7 group (CAE 7 group), a caerulein 7 plus LPS group (CAE 7 + LPS group), a caerulein 13 group (CAE 13 group), and a caerulein 13 plus LPS group (CAE 13 + LPS group). All the animals were killed three hours after the last intraperitoneal injection. The pancreas was carefully removed for microscopic examination and further observed under a transmission electron microscope (TEM). Serum amylase and lipase concentrations were assayed.

RESULTS: Enzyme levels and pathological score in all the experimental groups were significantly higher than those in the CON group (amylase lowest CAE 7 group: 27020 U/dL ± 3443 U/dL vs CON group: 2696 U/dL ± 400 U/dL, P < 0.01; lipase content lowest CAE 7 group: 1379 U/L ± 283 U/L vs CON group: 33 U/L ± 13 U/L, P < 0.01; pathological score lowest CAE 7 group: 5.8 ± 0.9 vs CON group: 0.1 ± 0.3, P < 0.01). Compared with the CAE 7 group, the enzyme levels and pathological score in the CAE 13 + LPS group increased more significantly (CAE 13 + LPS group amylase: 46969 U/dL ± 11852 U/dL vs CAE 7 group amylase: 27020 U/dL ± 3443 U/dL, P < 0.01; CAE13 + LPS group lipase: 1962 U/dL ± 496 U/dL vs CAE 7 group lipase: 1379 U/dL ± 283 U/dL, P < 0.05; CAE13 + LPS group pathological score : 11.1 ± 1.1 vs CAE 7 group pathological score : 5.8 ± 0.9, P < 0.05). The grade of pathological changes in the CAE 13 + LPS group was significantly higher than that in the CAE 13 group (CAE 13 + LPS group: 11.1 ± 1.1 vs CAE 13 group: 10.1 ± 0.99, P < 0.05). The ultrastructure of acinar cells was damaged in the CAE 7 group, and the rough endoplasmic reticulum and mitochondria were markedly swollen. However, in the CAE 13 + LPS group, the acinar cells were seriously damaged.

CONCLUSION: Caerulein alone by intraperitoneal injection 7 times can be used to prepare a typical model of acute edematous pancreatitis, and caerulein by intraperitoneal injection 13 times plus LPS at the last time can be used to produce typical acute necrotizing pancreatitis.

Gene expression changes in rat pancreas transplant model after long-term cold storage of the graft in perfluorohexyloctane

BACKGROUND

Perfluorohexyloctane (PFH) is a promising storage solution that has been successfully used for pancreas preservation before islet isolation. This hyperoxygen carrier has been designed to prevent ischemic injury to the pancreas graft during cold storage. In our storage, we aimed to evaluate the impact of this solution on long-term cold storage in a rat whole pancreas transplantation model.

METHOD

Brown-Norway rats were used for syngeneic heterotopic pancreas transplantation. The procured organs were cold-stored for 18 hours in preoxygenated PFH (PFH group; n = 8) or in the University of Wisconsin solution (UW group; n = 8), or were transplanted immediately in the control group (n = 8). Two hours after reperfusion, we obtained blood and pancreas tissue samples for biochemistry and gene analyses (real-time polymerase chain reaction).

RESULTS

A significant difference between the UW and PFH group was observed in the tumor necrosis factor (TNF)β and endothelin 1 genes, which was overexpressed more than twofold in the UW group. In the blood samples, the UW group compared with the PFH group showed significantly higher levels of pancreatic amylase and lipase (94.2 ± 25.2 vs 67.7 ± 13.4 μkat/L and 5.5 ± 2.8 vs 3 ± 0.7 μkat/L, respectively; P < .05).

CONCLUSION

We found significantly lower expression levels of the endothelin 1 and TNFβ genes and lower concentrations of pancreatic amylase and lipase in the PFH group. All these findings suggest lower rate of ischemic reperfusion injury in the PFH group. These findings may result in better post-transplant outcomes after long-term cold storage in PFH compared with the UW solution. Further research in this area is required.