Effects of cycloheximide on pancreatic endonuclease activity, apoptosis, and severity of acute pancreatitis

Inhibition of RIPK1-dependent regulated acinar cell necrosis provides protection against acute pancreatitis via the RIPK1/NF-κB/AQP8 pathway

Currently, preliminary results have confirmed the existence of receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL)-dependent necroptosis of pancreatic acinar cells during early acute pancreatitis (AP), which might be a potential target for the effective regulation of necroinflammatory injury. However, the exact effect of receptor-interacting protein kinase 1 (RIPK1)-dependent regulated acinar cell necrosis on AP is still uncertain. In our study, we first explored the changes in the degree of local and systemic inflammation in AP rats when the activation of acinar cell RIPK1 was inhibited. The RIPK1 inhibitor Nec-1 was used to treat rats, and the levels of related inflammatory markers, necrosis indicators and apoptotic indicators were measured. Changes in pancreatic nuclear factor κB (NF-κB) and aquaporin 8 (AQP8) expression were noted. Next, the expression of AQP8 in AR42J cells was inhibited, and the degree of cell necrosis and inflammatory damage was found to be significantly reduced. Most importantly, we demonstrated that the RIPK1/NF-ĸB/AQP8 axis might be a potential regulatory pathway mediating RIPK1-dependent regulated acinar cell necrosis in early AP. Finally, we used the NF-κB inhibitor PDTC and Nec-1 to treat rats in different groups and measured the degree of pathological pancreatic injury, the activation of RIPK1, and the expression of NF-κB and AQP8. In summary, we hypothesized that there might be a RIPK1/NF-ĸB/AQP8 pathway controlling RIPK1-dependent regulated necrosis of acinar cells in AP, which might be a promising therapeutic target against AP-related injury.

Serum levels of caspase-cleaved cytokeratin 18 (CK18-Asp396) predict severity of liver disease in chronic hepatitis B

Background and aim

Caspase-cleaved cytokeratin 18 (CK18-Asp396) is a potential clinically useful biomarker in liver disease as it is released from hepatocytes during apoptosis. In this study, we investigated serum CK18-Asp396 levels in chronic hepatitis B (CHB).

Patients and methods

Overall, 163 patients with CHB were included. Serum CK18-Asp396 levels were determined by enzyme-linked immunosorbent assay (ELISA), and results were related to steatosis grade, histological activity index, inflammation score, and METAVIR fibrosis grade as well as to viral load, serum levels of liver enzymes, and albumin. Receiver operating characteristic analysis was used to evaluate the diagnostic performance of serum CK18-Asp396 levels for assessing disease activity.

Results

A higher level of serum CK 18 concentrations was found in patients with significant inflammation vs no significant inflammation (378.5 [interquartile range {IQR}: 173.2–629.6] vs 137.3 [87.5–197.7], P < 0.05; approximately threefold increase) and in patients with significant fibrosis vs no significant fibrosis (177.8 [IQR: 120.8–519.1] vs 142.7 [IQR: 88.8–214.4], P < 0.05; 1.25-fold increase). There was no differential CK 18 level by degree of steatosis. CK 18 was an independent predictor of significant inflammation with an 82% specificity and a 94% negative predictive value. We found the strongest correlation of CK 18 with alanine aminotransferase and aspartate aminotransferase (both r = 0.52; P < 0.001), but less with albumin (r = −0.24; P < 0.05) and viral load (log) (r = 0.19; P < 0.05).

Conclusion

CHB appears to be accompanied by continuous high levels of hepatocyte apoptosis as judged from serum CK 18, suggesting that elimination of the infected compartment constitutes a defensive strategy against disease. Accordingly, CK 18 works as an independent predictor of significant inflammation with a high specificity.

Expression of Fas (CD95/APO-1) and Fas ligand (FasL) in experimentally-induced acute pancreatitis

INTRODUCTION

Acinar cell death is a crucial event in acute pancreatitis (AP) and may occur either by apoptosis or necrosis. The aim of this study was to investigate the expression of the apoptosis associated proteins Fas and FasL in experimentally induced severe AP.

METHODS

AP was induced in 30 rats by injecting 0.2 ml of 4.5% sodium taurocholate solution into the biliopancreatic duct. Sham operated animals (n = 30) and 10 normal controls were used for comparisons. Animals were killed at 6, 12, 24, 48, 72 hr and 1 week after operation (five animals at each time point) and both serum and pancreatic tissue were obtained. The severity of AP was graded by morphological evaluation and by measuring serum amylase levels. Acinar cell apoptosis was detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay. Tissue expressions of Fas and FasL were evaluated by immunohistochemistry.

RESULTS

Sodium taurocholate injection resulted in severe acute necrotizing pancreatitis as early as six hr after taurocholate infusion with gradually increasing severity and a peak at 72 hr, and a significant increase of serum amylase at 6 and 12 hr. Apoptotic acinar cells were observed between 48 and 72 hr. The expression of both Fas and FasL in pancreatic tissue was induced in comparison with normal controls. Fas expression in AP was higher and statistically significant at 24 hr whereas FasL expression was consistently lower with a statistical significance observed at 12 hr when compared to sham-operated animals suggesting Fas upregulation and FasL downregulation in this model of AP.

CONCLUSIONS

Induction and sequential changes in the expressions of Fas and FasL occur during taurocholate induced severe AP in rats and their temporal modulation might associate with acinar cell death by apoptosis.

Effects of arsenic trioxide on the cerulein-induced AR42J cells and its gene regulation

OBJECTIVES

To study the molecular mechanism of arsenic trioxide-induced cell death on cerulein-stimulated AR42J cells.

METHODS

AR42J cells were incubated for 24 hours, and cerulein (10 nmol/L) and different concentrations of arsenic trioxide were added for another 24 hours. The cells were collected and analyzed for apoptosis and oncosis by using rhodamine 123 and propidium iodide staining, and the changes in the genes that related to cell death were detected by a gene chip.

RESULTS

After cerulein stimulation, apoptosis was significantly increased in the AR42J cells. The addition of arsenic trioxide increased the number of apoptotic cells, and the apoptotic index reached its peak in the 1-micromol/L group. Regarding oncosis, low concentrations of arsenic trioxide (0.5, 1, 2, and 4 micromol/L) reduced the development of oncosis, and in the 2-micromol/L group, it was most significant, whereas high concentration of arsenic trioxide (8 micromol/L) promoted the development of oncosis. A total of 96 genes related to apoptosis were detected, and 36 genes were differentially expressed.

CONCLUSIONS

Appropriate concentrations of arsenic trioxide can induce apoptosis in AR42J cells that were induced by cerulein and lead to changes in the expressions of certain genes.

Induction of apoptosis by artemisinin relieving the severity of inflammation in caerulein-induced acute pancreatitis

AIM

To observe the apoptosis and oncosis of pancreatic acinar cells and secondary inflammatory reaction in pancreatic tissue from rats with acute pancreatitis (AP), and the influences of artemisinin on them.

METHODS

AP was induced by 4 intraperitoneal injections of caerulein at 1 h intervals. To induce apoptosis, solution of artemisinin (50 mg/kg) was given intraperitoneally 1, 12, 24 and 36 h after the last caerulein injection. Histological examination of impairment of pancreatic tissue and detection of serum amylase were performed to evaluate the severity of acute pancreatitis. Apoptosis and oncosis were detected with acridine orange (AO) and ethylene dibromide (EB) staining. Caspase-3 and myeloperoxidase (MPO) activity were measured by colorimetric assay. Nuclear factor-kappa B (NF-kappaB) activation was detected by flow cytometry. Macrophage inflammatory protein-1alpha (MIP-1alpha) protein was measured by Western blot. Interleukin-1beta (IL-1beta) mRNA was detected by RT-PCR.

RESULTS

Addition of artemisinin increased the number of apoptotic cells (11.7% +/- 1.4% vs 6.3% +/- 0.7%, P < 0.05), while reduced the number of oncotic cells (13.0% +/- 2.4% vs 17.5% +/- 2.2%, P < 0.05). The activity of caspase-3 speeded up (1.52 +/- 0.21 vs 1.03 +/- 0.08, P < 0.05), the pancreas pathological impairment was relieved (3.0 +/- 0.5 vs 4.0 +/- 0.5, P < 0.05) and the level of serum amylase decreased (5642 +/- 721 U/dL vs 7821 +/- 653 U/dL, P < 0.05). The activation of NF-kB (29% +/- 4.1% vs 42% +/- 5.8%), MIP-1alpha protein (3.7 +/- 0.5 vs 5.8 +/- 0.7), MPO (0.52 +/- 0.06 U/g vs 0.68 +/- 0.09 U/g), IL-1beta mRNA (1.7 +/- 0.3 vs 2.4 +/- 0.4) in the apoptosis inducing group was obviously decreased (P < 0.05).

CONCLUSION

Inducing apoptosis can relieve pathological impairment and inflammatory reaction in AP rats.

Induction of apoptosis by artemisinin relieving the severity of inflammation in caerulein-induced acute pancreatitis

AIM: To observe the apoptosis and oncosis of pancreatic acinar cells and secondary inflammatory reaction in pancreatic tissue from rats with acute pancreatitis (AP), and the influences of artemisinin on them.

METHODS: AP was induced by 4 intraperitoneal injections of caerulein at 1 h intervals. To induce apoptosis, solution of artemisinin (50 mg/kg) was given intraperitoneally 1, 12, 24 and 36 h after the last caerulein injection. Histological examination of impairment of pancreatic tissue and detection of serum amylase were performed to evaluate the severity of acute pancreatitis. Apoptosis and oncosis were detected with acridine orange (AO) and ethylene dibromide (EB) staining. Caspase-3 and myeloperoxidase (MPO) activity were measured by colorimetric assay. Nuclear factor-kappa B (NF-κB) activation was detected by flow cytometry. Macrophage inflammatory protein-1α (MIP-1α) protein was measured by Western blot. Interleukin-1β (IL-1β) mRNA was detected by RT-PCR.

RESULTS: Addition of artemisinin increased the number of apoptotic cells (11.7% ± 1.4% vs 6.3% ± 0.7%, P < 0.05), while reduced the number of oncotic cells (13.0% ± 2.4% vs 17.5% ± 2.2%, P < 0.05). The activity of caspase-3 speeded up (1.52 ± 0.21 vs 1.03 ± 0.08, P < 0.05), the pancreas pathological impairment was relieved (3.0 ± 0.5 vs 4.0 ± 0.5, P < 0.05) and the level of serum amylase decreased (5642 ± 721 U/dL vs 7821 ± 653 U/dL, P < 0.05). The activation of NF-κB (29% ± 4.1% vs 42% ± 5.8%), MIP-1α protein (3.7 ± 0.5 vs 5.8 ± 0.7), MPO (0.52 ± 0.06 U/g vs 0.68 ± 0.09 U/g), IL-1β mRNA (1.7 ± 0.3 vs 2.4 ± 0.4) in the apoptosis inducing group was obviously decreased (P < 0.05).

CONCLUSION: Inducing apoptosis can relieve pathological impairment and inflammatory reaction in AP rats.

Effects of large dose of dexamethasone on inflammatory mediators and pancreatic cell apoptosis of rats with severe acute pancreatitis

AIM: To investigate the influence of high dose of dexamethasone on inflammatory mediators and apoptosis of rats with severe acute pancreatitis (SAP).

METHODS: SAP rats were randomly assigned to the model group and treatment group while the normal rats were assigned to the sham operation group. The mortality, ascite volumes, ascites/body weight ratio and pancreas pathological changes of all rats were observed at 3, 6 and 12 h after operation. Their contents of amylase and endotoxin in plasma and contents of tumor necrosis factor (TNF-α), phospholipase A₂ (PLA₂) and IL-6 in serum were also determined. The microarray sections of their pancreatic tissues were prepared, terminal transferase dUTP nick end labeling (TUNEL) staining was performed and apoptotic indexes were calculated.

RESULTS: There was no marked difference between treatment group and model group in survival. The contents of amylase and endotoxin in plasma and contents of TNF-α, PLA₂ and IL-6 in serum, ascite volumes, ascites/body weight ratio and pancreas pathological scores were all lower in treatment group than in model group to different extents at different time points [P < 0.05, 58.3 (26.4) ng/L vs 77.535 (42.157) ng/L in TNF-α content, 8.00 (2.00) points vs 9.00 (2.00) points in pathological score of pancreas respectively; P < 0.01, 0.042 (0.018) EU/mL vs 0.056 (0.0195) EU/mL in endotoxin content, 7791 (1863) U/L vs 9195 (1298) U/L in plasma amylase content, 1.53 (0.79) vs 2.38 (1.10) in ascites/body weight ratio, 8.00 (1.00) points vs 11.00 (1.50) points in pathological score of pancreas; P < 0.001, 3.36 (1.56) ng/L vs 5.65 (1.08) ng/L in IL-6 content, 4.50 (2.00) vs 7.20 (2.00), 4.20 (1.60) vs 6.40 (2.30), 3.40 (2.70) vs 7.90 (1.70) in ascite volumes, respectively]. The apoptotic indexes of pancreas head and pancreas tail were all higher in treatment group than in model group at 6 h [P < 0.01, 0.00 (2.00)% vs 0.00 (0.00)%, 0.20 (1.80) vs 0.00 (0.00) in apoptosis indexes, respectively].

CONCLUSION: The mechanism of dexamethasone treatment in acute pancreatitis is related to its inhibition of inflammatory mediator generation and induction of pancreatic acinar cell apoptosis.

β2- and β3-Adrenoceptors activate glucose uptake in chick astrocytes by distinct mechanisms: a mechanism for memory enhancement?

Isoprenaline, acting at beta-adrenoceptors (ARs), enhances memory formation in single trial discriminated avoidance learning in day-old chicks by mechanisms involving alterations in glucose and glycogen metabolism. Earlier studies of memory consolidation in chicks indicated that beta3-ARs enhanced memory by increasing glucose uptake, whereas beta2-ARs enhance memory by increasing glycogenolysis. This study examines the ability of beta-ARs to increase glucose uptake in chick forebrain astrocytes. The beta-AR agonist isoprenaline increased glucose uptake in a concentration-dependent manner, as did insulin. Glucose uptake was increased by the beta2-AR agonist zinterol and the beta3-AR agonist CL316243, but not by the beta1-AR agonist RO363. In chick astrocytes, reverse transcription-polymerase chain reaction studies showed that beta1-, beta2-, and beta3-AR mRNA were present, whereas radioligand-binding studies showed the presence of only beta2- and beta3-ARs. beta-AR or insulin-mediated glucose uptake was inhibited by phosphatidylinositol-3 kinase and protein kinase C inhibitors, suggesting a possible interaction between the beta-AR and insulin pathways. However beta2- and beta3-ARs increase glucose uptake by two different mechanisms: beta2-ARs via a Gs-cAMP-protein kinase A-dependent pathway, while beta3-ARs via interactions with Gi. These results indicate that activation of beta2- and beta3-ARs causes glucose uptake in chick astrocytes by distinct mechanisms, which may be relevant for memory enhancement.

Progress of study on the relationship between mediators of inflammation and apoptosis in acute pancreatitis

As an important pathological feature of acute pancreatitis, apoptosis may occur in multiple organs and relate directly to the progression of disease. It is mainly controlled by the apoptosis gene and also influenced by inflammatory mediators. We summarize here the roles of the main inflammatory mediators (e.g., NO, TNF-alpha, TGF-beta1, IL-10, NF-kappaB) during the pathologic process of acute pancreatitis.

Suppressive effect of herbal medicine saikokeishito on acinar cell apoptosis in rat spontaneous chronic pancreatitis

BACKGROUND/AIMS

Chronic pancreatitis is characterized by acinar destruction and fibrosis. We previously reported that apoptosis is involved in acinar destruction in chronic pancreatitis in the WBN/Kob rat. This study aimed to elucidate the antiapoptotic effect of Saikokeishito (TJ-10).

METHODS

Four-week-old male WBN/Kob rats were fed a special pellet diet (MB-3) with or without TJ-10 (80 mg/100 g body weight) for 20 weeks. Pancreas was histopathologically examined every 4 weeks, and the expression of apoptosis-related factors such as Fas and Fas ligand (FasL) mRNA and protein was analyzed with RT-PCR, in situ hybridization and immunohistochemistry. Apoptosis was detected with a TUNEL method.

RESULTS

In untreated WBN/Kob rats, chronic pancreatitis developed at 12 weeks and progressed with marked acinar cell destruction at 16 weeks. The expression of Fas and FasL peaked at 12 and 20 weeks. An apoptotic index in acinar cells correlated to the expression of Fas and FasL mRNA. However, in the TJ-10-treated rats, the rate of pancreatic acinar cell destruction, the apoptotic index at 12-20 weeks, and the expression of Fas and FasL at 12 and 20 weeks decreased significantly compared to those in untreated rats.

CONCLUSION

These results suggest that TJ-10 has a therapeutic effect on chronic pancreatitis by the suppression of acinar cell apoptosis via the Fas/FasL system.

Cell death pathways in pancreatitis and pancreatic cancer

The understanding of the regulation of apoptosis and necrosis, the two principal cell death pathways, is becoming exceedingly important in investigations of the pathogenesis and treatment of pancreatitis and pancreatic cancer. For example, in acute pancreatitis significant amounts of pancreatic necrosis are associated with increased morbidity and mortality. Thus, determining the key steps regulating necrosis should provide insights into potential therapeutic strategies for improving outcome in these patients. On the other hand, in pancreatic cancer various survival mechanisms act to prevent cell death, resulting in promotion of tumor growth and metastasis. Resistance of pancreatic cancer to apoptosis is the key factor preventing responses to therapies. Investigations of the regulation of cell death mechanisms specific to pancreatic cancer should lead to improvements in our current therapies for this disease. The present review is designed to provide information about cell death pathways in pancreatitis and pancreatic cancer with reference to areas that need further investigation, as well as to provide measurement techniques adapted to pancreatic tissue and cells.

Increased expression of hypoxia-inducible factor-1alpha, p48, and the Notch signaling cascade during acute pancreatitis in mice

Acute pancreatitis (AP) is a complex disease that may be linked to acinar cell apoptosis and inadequate acinar cell replacement. Differentiation of acinar cells is regulated by p48, a DNA binding subunit of the transcription factor PTF1, and the Notch signaling pathway. Acinar cell apoptosis is triggered by oxygen deprivation, ie, hypoxia, by activation of hypoxia inducible factor-1alpha (HIF-1alpha). The aim of this study was to characterize by Northern blot analyses expression of HIF-1alpha, HIF-1alpha-inducible genes (GLUT-1, VEGF, p53), p48, and genes involved in the Notch signaling pathway (Notch-1, Dll1, RBP-Jk, HES-1) during cerulein-induced AP in mice. Maximal expression of HIF-1alpha, HIF-1alpha-inducible genes, p48, and Notch signaling genes occurred 8-12 hours after induction of AP. Maximal expression of p53 occurred 12-48 hours after induction of AP. These findings demonstrate that multiple pancreatic genes are activated acutely during AP that support pancreatic cell replenishment, regulation of expression of acinar cell-specific genes, and apoptosis.

Oxidative stress induces nuclear loss of DNA repair proteins Ku70 and Ku80 and apoptosis in pancreatic acinar AR42J cells

Cell death linked to oxidative DNA damage has been implicated in acute pancreatitis. The severe DNA damage, which is beyond the capacity of the DNA repair proteins, triggers apoptosis. It has been hypothesized that oxidative stress may induce a decrease in the Ku70 and Ku80 levels and apoptosis in pancreatic acinar cells. In this study, it was found that oxidative stress caused by glucose oxidase (GO) acting on beta-d-glucose, glucose/glucose oxidase (G/GO), induced slight changes in cytoplasmic Ku70 and Ku80 but drastically induced a decrease in nuclear Ku70 and Ku80 both time- and concentration-dependently in AR42J cells. G/GO induced apoptosis determined by poly(ADP-ribose) polymerase cleavage, an increase in expression of p53 and Bax, and a decrease in Bcl-2 expression. G/GO-induced apoptosis was in parallel with the loss of nuclear Ku proteins in AR42J cells. Caspase-3 inhibitor prevented G/GO-induced nuclear Ku loss and cell death. G/GO did not induce apoptosis in the cells transfected with either the Ku70 or Ku80 expression gene but increased apoptosis in those transfected with the Ku dominant negative mutant. Pulse and pulse-chase results show that G/GO induced Ku70 and Ku80 syntheses, even though Ku70 and Ku80 were degraded both in cytoplasm and nucleus. G/GO-induced decrease in Ku binding to importin alpha and importin beta reflects possible modification of nuclear import of Ku proteins. The importin beta level was not changed by G/GO. These results demonstrate that nuclear decrease in Ku70 and Ku80 may result from the decrease in Ku binding to nuclear transporter importins and the degradation of Ku proteins. The nuclear loss of Ku proteins may underlie the mechanism of apoptosis in pancreatic acinar cells after oxidative stress.

Acute pancreatitis signals activation of apoptosis-associated and survival genes in mice

In experimental models of acute pancreatitis (AP), acinar cell death occurs by both necrosis and programmed cell death or apoptosis. Apoptosis is an active form of cell death associated with a tightly regulated expression of gene products that are either pro- or antiapoptotic. The aim of this study was to characterize pancreatic mRNA levels by Northern blotting analysis of apoptosis-associated genes used during the course of cerulein-induced AP in mice. Histone H3 mRNA levels were also examined as an indicator of cell proliferation. Acinar cell apoptosis was confirmed histologically. The findings show that AP modifies pancreatic mRNA levels of both pro- and antiapoptotic genes simultaneously. Pancreatic bclXL, bax, and p53 mRNA levels increased significantly in a temporal fashion during induction of AP. Pancreatic bcl-2 mRNA levels were unchanged during AP. Pancreatic mRNA levels of insulin-like growth factor-1 (IGF-1), a mitogen and cell survival factor, and its receptor (IGF-1R) also increased in a temporal fashion during induction of AP. In summary, this study indicates that acinar cell death during cerulein-induced AP in mice can occur by the apoptotic pathway. Since factors promoting and antagonistic for cell survival are activated simultaneously, regulation of acinar cell survival appears complex and dynamic during AP.

Anti-ICAM-1 antibody modulates late onset of acinar cell apoptosis and early necrosis in taurocholate-induced experimental acute pancreatitis

The hallmark of severe acute pancreatitis (SAP) is massive acinar cell death by necrosis. However, programmed, apoptotic acinar cell death has also been observed. Little is known about the dynamics, localization, and inductive factors of acinar cell apoptosis in SAP. We therefore induced SAP in rats by retrograde infusion of 3% sodium taurocholate. Starting as early as 5 minutes after taurocholate administration, small scattered groups of acinar cells showed zymogen degranulation, loss of cell polarity, cytoplasmic microvacuolization, and nuclear shrinkage, but no DNA degradation, thus featuring necrosis. The areas of necrotic acini extended at later time points giving rise to larger areas of complete parenchymal breakdown after 6 hours. Parenchymal degradation was paralleled by neutrophil infiltration and significant tumor necrosis factor (TNF)-alpha mRNA up-regulation. Up to the 12-hour interval, apoptotic acinar cells detected by TUNEL were as rare as in healthy pancreata. At 24 hours, however, the acinar apoptotic rate in nonnecrotic parenchyma had dramatically increased. Pretreatment of rats with anti-ICAM-1 antibody prior to pancreatitis induction led to a significant reduction of neutrophil infiltration along with decreased TNF-alpha mRNA expression throughout the 24-hour observation period without affecting the presence and dynamics of necrosis. However, anti-ICAM-1 pretreatment decreased the extent of acinar cell damage by necrosis and extensively suppressed acinar cell apoptosis. We conclude that taurocholate induces two sequential patterns of acinar cell death in terms of very early necrosis followed by late apoptosis during the postacute phase of SAP. The progression of necrosis and the late apoptotic acinar cell death seem to be influenced by the local presence of neutrophils via a TNF-alpha-dependent mechanism. In addition to augmenting necrosis, neutrophils might have an apoptosis-inducing potential in SAP.

Effects and mechanisms of somatostatin analogs on apoptosis of pancreatic acinar cells in acute pancreatitis in mice

AIM

To investigate the effects of somatostatin analogs (SSa) on apoptosis of pancreatic acinar cells and apoptosis-regulated gene bax, and p53 in treating acute pancreatitis in mice.

METHODS

In cerulein-induced pancreatitis, with or without treatment of somatostatin, analogs (Octreotide) in CD-1 (BALB/c x DBetaAlpha/1) mice, apoptosis of pancreatic acinar cells was detected by using the TdT-mediated dUTP nick-end labeling (TUNEL) method, and the expression of apoptosis-regulated gene bax and p53 was determined by using the streptavidin-peroxidase immunohistochemical technique and the RT-PCR method, respectively.

RESULTS

On HE staining, acinar cells in the pancreas showed pyknotic nuclei and the formation of apoptotic bodies, which are the typical morphological features of apoptosis. Regarding TUNEL use, the apoptotic index of pancreatic acinar cells in the non-treated group at 5 and 14 h after induction of acute pancreatitis was significantly lower than those of the SSa-treated group, respectively (P < 0.01). On immunohistochemistry and RT-PCR, there was an expression of neither bax nor p53 in normal pancreatic tissues. The expression of bax in the SSa-treated group at 5 and 14 h after treatment of SSa was markedly higher than those of the non-treated group, respectively (P < 0.01), but there was no significant difference in the expression of p53 between the SSa-treated group and the non-treated group.

CONCLUSIONS

The induction of apoptosis in pancreatic acinar cells injury to reduce inflammatory reaction might be one of the mechanisms of SSa in treating acute pancreatitis in mice, and the mechanisms of apoptosis probably correlated with the expression of apoptosis-regulated gene bax, but have no relationship with the expression of p53.

Tumor necrosis factor alpha triggers antiapoptotic mechanisms in rat pancreatic cells through pancreatitis-associated protein I activation

BACKGROUND & AIMS

Tumor necrosis factor (TNF)-alpha contributes to the development of acute pancreatitis. Because TNF-alpha is involved in the control of apoptosis, we studied its interaction with the pancreatic apoptotic pathway.

METHODS

Pancreatic acinar AR4-2J cells were used. Apoptosis was monitored by morphologic and biochemical criteria.

RESULTS

TNF-alpha induced apoptosis in AR4-2J cells. Induction was strongly enhanced in cells treated with actinomycin D, suggesting that TNF-alpha activated concomitantly an antiapoptotic mechanism through newly synthesized proteins. This mechanism involved activation of nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein (MAP) kinases because their inhibition worsened TNF-alpha-induced apoptosis. The antiapoptotic pancreatitis-associated protein (PAP) I is a candidate for mediating TNF-alpha activity. Its expression is induced by TNF-alpha, and cells overexpressing PAP I show significantly less apoptosis on exposure to TNF-alpha. We examined whether TNF-alpha induction of PAP I expression was mediated by NF-kappaB or MAP kinases by using specific inhibitors of both pathways. Inhibition of NF-kappaB had no effect. However, inhibitors of MEK1 eliminated PAP I induction.

CONCLUSIONS

TNF-alpha induces concomitantly proapoptotic and antiapoptotic mechanisms in pancreatic AR4-2J cells. Antiapoptotic mechanisms are mediated by NF-kappaB and MAP kinases, and PAP I is one of the effectors of apoptosis inhibition.

Water immersion stress induces heat shock protein 60 expression and protects against pancreatitis in rats

BACKGROUND & AIMS

Heat shock proteins (Hsps), induced by cell stress, are known to protect against cellular injury. Recent studies have indicated that Hsp60 expression, induced by exposure to water immersion stress, protects against pancreatitis induced by administration of supramaximal doses of cerulein in rats. However, the mechanisms responsible for this protection are not known.

METHODS

Rats were water-immersed for 3-12 hours. Pancreatitis was induced by cerulein administration.

RESULTS

The results confirm that prior induction of Hsp60 expression by water-immersion stress significantly ameliorates the severity of cerulein-induced pancreatitis as judged by the markedly reduced degree of hyperamylasemia, pancreatic edema, and acinar cell necrosis. Water immersion also prevents the subcellular redistribution of cathepsin B from a lysosome-enriched fraction to a heavier, zymogen granule-enriched fraction that is known to occur in this model of pancreatitis. Intra-acinar cell activation of trypsinogen that occurs shortly after exposure to a supramaximally stimulating dose of cerulein both in vivo and in vitro is prevented by prior water-immersion stress and Hsp60 expression. The protection against pancreatitis that follows water-immersion stress is not caused by alterations of cholecystokinin receptors, because water immersion does not alter the typical biphasic amylase secretory response to stimulation with cerulein.

CONCLUSIONS

Water-immersion stress induces Hsp60 expression, ameliorates cerulein-induced pancreatitis, and prevents intra-acinar cell activation of trypsinogen. We suggest that Hsp60 protects against cerulein-induced pancreatitis by preventing trypsinogen activation within acinar cells.

Repetitive short-term obstructions of the common bile-pancreatic duct induce severe acute pancreatitis in the opossum

Gallstone pancreatitis is triggered by migrating stones that cause transient or continuous bile-pancreatic duct obstruction. One might hypothesize that the great clinical variability of acute pancreatitis is related to the inconsistent number and duration of a series of stone migrations. A new setting for the opossum model of acute pancreatitis was developed allowing reversible bile-pancreatic duct obstructions. We compared the effects, on the pancreas and pancreatitis severity, of repeated transient obstructions to those of continuous obstruction of varying duration. Repetitive intermittent duct obstruction in American opossums was achieved using an extraductal balloon occluder connected to a subcutaneous port system that was inflated three times for 24 hr within a five-day period. Continuous duct obstruction was achieved by duct ligation. Sham-operated animals served as controls. After one, three, or five days of continuous obstruction and at the end of the third consecutive 24-hr obstruction (day 5), animals were killed and the severity of pancreatitis was determined quantitating the extent of acinar cell necrosis, pancreatic edema, and acinar cell fragility. Three repetitive one-day periods (total 72 hr) of bile-pancreatic duct obstruction resulted in acute necrotizing pancreatitis. The severity of pancreatitis was similar to that observed after five days of continuous obstruction and was more severe than that noted after three days (72 hr) of continuous obstruction. In conclusion, these observations suggest that the pancreas is susceptible to sensitization by factors related to transient duct obstruction. A series of minor events such as repeated stone passage may thus contribute to the progression to severe pancreatitis.

The potential role of therapeutic cytokine manipulation in acute pancreatitis

The central, detrimental role of the inflammatory cytokines IL-1 and TNF and the biologically active phospholipid PAF in the pathogenesis of AP has been established over the past 8 years. A number of antagonists to these mediators have been used successfully in the laboratory setting and are currently being examined in prospective randomized trials. The effectiveness of any antagonist depends not only on its ability to block the effects of the inflammatory mediators but also on its administration early enough in the course of the pancreatitis before pancreatic necrosis or organ dysfunction.

Induction of apoptosis in pancreatic acinar cells reduces the severity of acute pancreatitis

1-Cyano-2-hydroxy-3-butene (CHB) has been reported to cause cell death in rat pancreatic acini. In this report, we describe the time-dependent effects of CHB on mouse acinar cell apoptosis and the effects of CHB-induced acinar cell apoptosis on the severity of secretagogue-induced acute pancreatitis in mice. CHB administration to mice resulted in a time-dependent increase in pancreatic apoptosis, which was maximal 12 hours after CHB administration. The severity of pancreatitis was significantly reduced by prior CHB administration and maximal protection was observed when the caerulein injections were started 12 hours after CHB administration. These observations indicate that induction of apoptosis can reduce the severity of pancreatitis and they suggest that induction of pancreatic acinar cell apoptosis may be beneficial in the clinical management of acute pancreatitis.

Endogenous glucocorticoids decrease the acinar cell sensitivity to apoptosis during cerulein pancreatitis in rats

BACKGROUND & AIMS

We recently showed that activation of the hypothalamus-pituitary-adrenal axis may mitigate the progress of acute pancreatitis. To clarify the mechanism, the role of endogenous glucocorticoids in pancreatic acinar cell death was examined.

METHODS

The occurrence of apoptosis was studied in adrenalectomized or sham-operated rats with or without cerulein-induced pancreatitis. The effects of RU38486, a glucocorticoid-receptor antagonist, on the survival of cultured acinar cells (AR42J) were also examined.

RESULTS

Adrenalectomy caused increases in terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) of acinar nuclei depending on the time after adrenalectomy but not of other cell types in the pancreas and in other digestive organs. Electron microscopy showed the characteristic features of apoptosis in the TUNEL-labeled acinar cells. In cerulein pancreatitis of adrenalectomized rats, the TUNEL-labeled acinar nuclei increased remarkably depending on the time after cerulein infusion. Replacement of glucocorticoids blocked the occurrence of apoptosis in these experiments. RU38486 induced dose dependently the apoptosis of AR42J cells.

CONCLUSIONS

These results provide evidence that endogenous glucocorticoids are an important factor for acinar cell survival. Endogenous glucocorticoids may protect acinar cells by decreasing their sensitivity to the induction of cell death during acute pancreatitis.

The role of cytokines in the pathogenesis of acute pancreatitis

BACKGROUND

The systemic manifestations of acute pancreatitis are responsible for the majority of pancreatitis-associated morbidity and mortality and are now believed to be due to the actions of specific inflammatory cytokines. This report summarizes what is known about the role of cytokines in the pathogenesis of acute pancreatitis.

METHODS

Comprehensive literature review of experimental pancreatitis as well as all reports of cytokine involvement during clinical pancreatitis.

RESULTS

Several cytokines and other noncytokine inflammatory mediators are produced rapidly during pancreatitis. These mediators arise in many tissues in a predictable fashion independent of the animal model used or the underlying etiology in human disease. Preventing the activities of these mediators has a profound beneficial effect in experimental animals.

CONCLUSIONS

A few recently described inflammatory mediators are believed to be primarily responsible for the systemic manifestations of acute pancreatitis and its associated distant organ dysfunction. The predictable nature in which they are produced may allow for novel approaches to treating this disease. Am J Surg.