Bile and pancreatic juice replacement ameliorates early ligation-induced acute pancreatitis in rats

Murine pancreatic duct ligation induces stress kinase activation, acute pancreatitis, and acute lung injury

BACKGROUND

Acute lung injury is a major determinant of outcomes in acute pancreatitis. We evaluated acute lung injury and stress kinase activation in ligation-induced acute pancreatitis in mice.

METHODS

Mice with duct ligation or sham operation were killed after 24 or 48 hours.

RESULTS

In addition to acute pancreatitis, duct ligation was associated with pulmonary morphologic changes indicative of acute lung injury (alveolar septal thickening, congestion, and neutrophil infiltration). Furthermore, immunoblotting showed stress kinase activation in the pancreas and lung after ligation. Although mortality was observed in the ligated group, that is consistent with severe lung injury, it requires further evaluation.

CONCLUSIONS

Bile and pancreatic duct ligation in the mouse is associated with pancreatic and pulmonary stress kinase activation and acute inflammatory changes consistent with early acute pancreatitis and acute lung injury. Our findings are important as acute lung injury increases mortality in clinical acute pancreatitis and stress kinases are established proinflammatory signal transducers.

Enteral exclusion increases MAP kinase activation and cytokine production in a model of gallstone pancreatitis

BACKGROUND

We have previously demonstrated that enteral exclusion augments pancreatic p38 mitogen-activated protein (MAP) kinase activation and tumor necrosis factor-alpha (TNF-alpha) production after bile-pancreatic duct ligation in rats.

METHODS

In the present study, we evaluated c-Jun NH(2)-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) activation, and cytokine production, in pancreata of duct-ligated rats with and without duodenal bile-pancreatic juice replacement from a donor rat. We hypothesized that enteral exclusion of bile-pancreatic juice activates stress kinases and induces cytokine production in ligation-induced acute pancreatitis.

RESULTS

Increased JNK and ERK activation after ligation are inhibited by bile-pancreatic juice replacement. Increases in pancreatic production of IL-1beta and IL-12 after ligation are significantly subdued by replacement. In additional in vitro studies, we show that cholecystokinin- or TNF-alpha-stimulated nuclear transcription factor kappa-B activation in AR42J cells is inhibited by dominant negative ERK2.

CONCLUSIONS

Our novel findings using our Donor Rat Model indicate that bile-pancreatic juice exclusion induces MAP kinase activation and exacerbates cell stress and inflammation in this experimental model of gallstone pancreatitis. and IAP.

Bile and pancreatic juice exclusion activates acinar stress kinases and exacerbates gallstone pancreatitis

HYPOTHESIS

Bile and pancreatic juice exclusion from gut activates acinar stress kinases and exacerbates gallstone pancreatitis as evidenced by the ameliorating effects of replacement therapy in an experimental model of duct ligation-induced acute pancreatitis. In the early stages of gallstone pancreatitis, bile-pancreatic juice cannot enter the gut. Enteral exclusion worsens pancreatitis by causing feedback hyperstimulation of the exocrine pancreas that activates acinar cell stress kinases. Investigations using a unique surgical model, the Donor Rat Model, showed that duodenal replacement of bile-pancreatic juice in rats with duct ligation attenuates pancreatic stress kinase activation, reduces pancreatic cytokine production, and ameliorates pancreatic morphologic changes. These findings suggest that exclusion-induced acinar hyperstimulation, in the presence of duct obstruction, exacerbates acute pancreatitis via stress kinase activation. Although acinar hyperstimulation has often been implicated in the pathogenesis of acute pancreatitis, the lack of supporting evidence remains a conspicuous void. The proposed hypothesis draws on fresh evidence to present a new paradigm that reexamines the role of exocrine pancreatic hyperstimulation in gallstone pancreatitis pathogenesis.

Morphologic characterization of early ligation-induced acute pancreatitis in rats

BACKGROUND

Bile-pancreatic duct ligation in rats causes acute pancreatic inflammation. We performed serial morphologic evaluation of the exocrine pancreas after duct ligation to facilitate further investigations using the model.

METHODS

The pancreas was excised from 74 rats after 0, 1, 3, 5, 24 or 48 hours of duct ligation or sham surgery. A pathologist evaluated 1 hematoxylin- and eosin-stained slide from each rat. Confirmatory immunostaining was performed with markers for apoptosis (activated caspase-3), proliferation (cyclin D3), neutrophils (myeloperoxidase), and macrophages (CD68).

RESULTS

Interstitial edema and white blood cell infiltration were apparent at 24 hours and increased at 48 hours. Progressive periods of duct ligation were characterized by ductular ectasia (1 to 3 hours), acinar vacuolization (5 to 48 hours), leukocytic margination and neutrophil exocytosis (5 to 48 hours), ductule epithelium hypertrophy and proliferation (24 to 48 hours), and discernible loss of zymogen granules (48 hours).

CONCLUSIONS

Ligation-induced acute pancreatitis in rats is a useful model to investigate early events in disease pathogenesis.

In vitro evidence for role of ERK, p38, and JNK in exocrine pancreatic cytokine production

Elucidation of mechanisms of acinar cell cytokine production is essential for a better understanding of acute pancreatitis pathogenesis. We hypothesize that the stress kinases ERK, p38, and JNK play an important role in acinar cell cytokine production. Rat pancreatic fragments were incubated with 100 nM concentration of the cholecystokinin analog caerulein or 100 nM caerulein and specific ERK inhibitor (100 microM PD98059), specific p38 inhibitor (10 microM SB203580), or specific JNK inhibitor (20 microM SP600125). After 3 hours of caerulein treatment, pancreatic fragments were homogenized and assayed for total and phosphorylated ERK, p38, and JNK, and for tumor necrosis factor-alpha or interleukin-1beta concentrations (ELISA). Pancreatic fragments stimulated with caerulein showed activation of ERK, p38, and JNK and increased cytokine concentrations (ANOVA, P<0.05). Specific stress kinase inhibitors significantly attenuated caerulein-induced activation of the corresponding stress kinase and cytokine production; however, the effect of the JNK inhibitor was comparatively less convincing. Increased activation of ERK, p38, and JNK in pancreatic fragments was not associated with significant increases in total ERK, total p38, or total JNK concentrations. The stress kinases ERK and p38 play an important role in caerulein-stimulated exocrine pancreatic overproduction of cytokines. The role of JNK needs further evaluation in this experimental model.

Bile-pancreatic juice exclusion promotes Akt/NF-kappaB activation and chemokine production in ligation-induced acute pancreatitis

Using a unique surgical model (the donor rat model), we showed previously that duodenal replacement of bile-pancreatic juice, obtained fresh from a donor rat, ameliorates ligation-induced acute pancreatitis. We hypothesize that bile-pancreatic juice exclusion from gut exacerbates Akt/nuclear factor-kappaB (NF-kappaB) pathway activation and induces chemokine production in ligation-induced acute pancreatitis. We compared rats with bile-pancreatic duct ligation to those with duodenal bile-pancreatic juice replacement fresh from a donor rat beginning immediately before duct ligation. Sham control rats had ducts dissected but not ligated. Rats were killed 1 or 3 hours after operation (n = 7/group). Akt activation (immunoblotting, immune-complex kinase assay, and ELISA), inhibitory protein I-kappaB (IkappaB) activation (immunoblotting), and production of chemokines MCP-1 and RANTES (ELISA) were measured in pancreatic homogenates. NF-kappaB was quantitated in nuclear fractions using electrophoretic mobility shift assay. Duct ligation produced significant increases in pancreatic Akt, IkappaB, and NF-kappaB activation and production of MCP-1 and RANTES. Activation of the Akt/NF-kappaB pathway and increased MCP-1 and RANTES production in response to duct ligation were significantly reduced by bile-pancreatic juice replacement (ANOVA, P < 0.05). Bile-pancreatic juice exclusion stimulates Akt/NF-kappaB pathway activation and increases chemokine production in ligation-induced acute pancreatitis.

Exacerbation of acute pancreatitis by combined cholinergic stimulation and duct obstruction

BACKGROUND

The role of cholinergic pathways in the pathogenesis of bile-pancreatic duct ligation (BPDL)-induced acute pancreatitis in rats remains controversial. We hypothesized that cholinergic stimulation exacerbates acute pancreatic inflammation in the presence of duct obstruction.

METHODS

We studied 34 rats divided into 5 groups as follows: (1) sham operation; (2) BPDL; (3) BPDL with duodenal bile-pancreatic juice (BPJ) replacement fresh from a donor rat; (4) BPDL with BPJ replacement as in 3 above, and carbachol (CCh) 5 ug/h subcutaneously; or (5) CCh 5 ug/h subcutaneously only. Rats were killed after 6 hours.

RESULTS

The P value was less than .05 by analysis of variance. Pancreatic morphologic changes and zymogen fraction hyperamylasemia seen with duct ligation (2 vs. 1) were ameliorated significantly by duodenal BPJ replacement (3 vs. 2), but not when exogenous CCh was administered (4 vs. 3), whereas CCh alone showed no significant changes compared with sham (5 vs. 1).

CONCLUSIONS

Cholinergic stimulation and duct obstruction synergistically amplify acinar hyperstimulation and exacerbate acute pancreatitis.

Bile-pancreatic juice exclusion increases p38MAPK activation and TNF-alpha production in ligation-induced acute pancreatitis in rats

Acute pancreatitis is associated with stress kinase activation and cytokine production. We hypothesize that bile-pancreatic juice exclusion activates p38(MAPK) and induces TNF-alpha production in ligation-induced acute pancreatitis. We compared rats with 1-3 h of duct ligation, duct ligation with duodenal bile-pancreatic juice replacement from a donor rat, and sham operation. Pancreatic homogenates were analyzed as follows: (a) Immunoblots using phospho-specific p38(MAPK) antibody showed increased p38(MAPK) activation after ligation that was inhibited by bile-pancreatic juice replacement. (b) Immune-complex kinase assay using ATF-2 as substrate showed increased p38(MAPK) activation after ligation that was subdued by bile-pancreatic juice replacement. (c) ELISA showed increased pancreatic TNF-alpha production after ligation that was significantly ameliorated by bile-pancreatic juice replacement.

CONCLUSION

Bile-pancreatic juice exclusion from gut increases p38(MAPK) activation and TNF-alpha production in this experimental model. Our findings support our central hypothesis that bile-pancreatic juice exclusion exacerbates cell stress and acute inflammation in ligation-induced acute pancreatitis.

Bile-pancreatic juice exclusion increases cholinergic M3 and CCK-A receptor expression and interleukin-6 production in ligation-induced acute pancreatitis

BACKGROUND

Using an original model, the Donor Rat Model, we showed that bile-pancreatic juice (BPJ) exclusion from gut exacerbates ligation-induced acute pancreatitis in rats. We also showed that muscarinic cholinergic M3 and CCK-A receptor expression is induced following duct ligation. Increased receptor number potentially could exacerbate cytokine production. We hypothesize that BPJ exclusion is responsible for M3 and CCK-A receptor induction and increased interleukin-6 (IL-6) production.

METHODS

M3 and CCK-A receptor expression and IL-6 production were compared in rat pancreata 1 to 3 hours after duct ligation with or without BPJ replacement.

RESULTS

Our studies showed that BPJ replacement attenuates duct ligation-induced increases in M3 and CCK-A receptor expression and IL-6 production.

CONCLUSIONS

In this model, BPJ exclusion from gut induces M3 and CCK-A receptor expression and increases IL-6 production. In this experimental corollary of gallstone pancreatitis, BPJ exclusion from gut may play a key role in the mechanism of disease pathogenesis.

Mechanism of acute pancreatitis exacerbation by enteral bile-pancreatic juice exclusion

Using an original model, the donor rat model, we previously showed that bile-pancreatic juice exclusion from gut exacerbates ligation-induced acute pancreatitis. Here, we examine the mechanism by which bile-pancreatic juice exclusion from gut exacerbates acute pancreatitis. In the first part of the study we test the hypothesis that Na taurocholate and trypsin are components of bile-pancreatic juice that exacerbate acute pancreatitis when excluded. Our experiments show that combined replacement of Na taurocholate and trypsin ameliorates acute pancreatitis. In the second part of the study we test the hypothesis that bile-pancreatic juice exclusion from gut exacerbates acute pancreatitis via combined CCK-A and cholinergic receptor pathways. Our experiments show that combined CCK-A and cholinergic receptor blockade significantly ameliorates acute pancreatitis while blockade of either receptor alone does not. We conclude that bile-pancreatic juice exclusion-induced exacerbation of ligation-induced acute pancreatitis involves a neurohormonal duodenal response to exclusion of trypsin and Na taurocholate resulting in acinar cell hyperstimulation via combined CCK-A and cholinergic receptor-mediated pathways.

CCK-A receptor induction and P38 and NF-kappaB activation in acute pancreatitis

Bile-pancreatic duct ligation in rats excludes bile-pancreatic juice from the gut and induces acute pancreatitis. Bile-pancreatic juice exclusion from the gut results in increased plasma cholecystokinin (CCK) levels. CCK-A receptor-mediated exocrine pancreatic hyperstimulation is implicated in disease pathogenesis. In the present study, we show for the first time a progressive rise in CCK-A receptor protein expression in ligation-induced acute pancreatitis in rats. As CCK-A receptor induction could amplify CCK-mediated acinar hyperstimulation and exacerbate acinar cell stress with activation of the p38(MAPK) stress kinase pathway, we studied CCK-A receptor protein expression and p38(MAPK) activation in duct ligation-induced acute pancreatitis in rats. Compared to sham-operated controls, acute pancreatitis induced by bile-pancreatic duct ligation associates with a temporal increase in pancreatic CCK-A receptor protein expression, p38(MAPK) expression and activation, and NF-kappaB activation. These findings may have significance in the mechanism of disease pathogenesis in this experimental model.

Cholinergic receptor induction and JNK activation in acute pancreatitis

BACKGROUND

Cholecystokinin-A (CCK-A) and cholinergic receptor pathways, capable of activating stress kinases p38 mitogen-activated protein kinase (p38(MAPK)) and cJUN N-terminal kinase (JNK), are implicated in the pathogenesis of ligation-induced acute pancreatitis in rats. As ligation-induced acute pancreatitis in rats is associated with CCK-A receptor induction and p38(MAPK) activation, and as receptor induction could amplify acinar hyperstimulation and exacerbate cell stress, we tested the hypothesis that the cholinergic M3 receptor is induced and JNK is activated in this model.

METHODS

Cholinergic M3 receptor expression and JNK activation was compared in rats 1, 3, or 24 hours after sham operation or duct ligation.

RESULTS

Immunoblot analysis of pancreatic homogenates showed a time-dependent increase in cholinergic M3 receptor protein, total JNK, and phospho-JNK after duct ligation.

CONCLUSIONS

There is a rapid and progressive cholinergic M3 receptor induction and JNK activation in ligation-induced acute pancreatitis in rats. These findings may have significance in the mechanism of disease pathogenesis.

Cholecystokinin acts as an essential factor in the exacerbation of pancreatic bile duct ligation-induced rat pancreatitis model under non-fasting condition

We examined the influence of 2 gut hormones involved in the enhancement of pancreatic exocrine secretion, secretin and cholecystokinin (CCK), in the exacerbation of pancreatitis. We also examined the role of the vagal system, which was considered to be a transmission route for these hormones. Our model of pancreatitis in the rat was prepared by pancreatic bile duct ligation (PBDL), which simultaneously ligated the pancreatic duct and the common bile duct. Serum amylase activity and histopathological changes in the pancreas were used as indices of pancreatitis. We also measured the volume of pancreatic juice, as well as the amylase activity and protein level of the pancreatic juice, as indices of increased pancreatic exocrine secretion. Two gut hormones were given 6 times at 1-h intervals. Administration of secretin (1-3 microg/kg, s.c.) did not influence serum amylase activity in rats with PBDL-induced pancreatitis. However, food stimulation and administration of CCK-8 (1 microg/kg, s.c.) increased serum amylase activity and promoted vacuolation of the pancreatic acinar cells in rats with PBDL-induced pancreatitis. Administration of atropine (3 mg/kg, s.c.) or a CCK1-receptor antagonist, Z-203 (0.1 mg/kg, i.v.), inhibited food-stimulated or CCK-8-induced (1 microg/kg, s.c.) enhancement of pancreatic exocrine secretion and exacerbation after the development of PBDL-induced pancreatitis. These results suggest that not secretin, which regulates the volume of pancreatic juice, but CCK, which regulates the secretion of pancreatic enzymes via the vagal system, plays an essential role in food-stimulated exacerbation after the development of pancreatitis.

Inducible Nitric Oxide Synthase Protection Against Coxsackievirus Pancreatitis

Coxsackievirus infection causes myocarditis and pancreatitis in humans. In certain strains of mice, Coxsackievirus causes a severe pancreatitis. We explored the role of NO in the host immune response to viral pancreatitis. Coxsackievirus replicates to higher titers in mice lacking NO synthase 2 (NOS2) than in wild-type mice, with particularly high viral titers and viral RNA levels in the pancreas. Mice lacking NOS have a severe, necrotizing pancreatitis, with elevated pancreatic enzymes in the blood and necrotic acinar cells. Lack of NOS2 leads to a rapid increase in the mortality of infected mice. Thus, NOS2 is a critical component in the immune response to Coxsackievirus infection.

Functional consequences of adenovirus-mediated murine pancreatic gene transfer

Pancreatic adenoviral gene transfer can be achieved with high efficiency; however, questions concerning tissue injury from this commonly used vector have not been addressed. In these experiments, the effects of adenoviral gene transfer on pancreatic exocrine function were evaluated. Direct pancreatic injection with an adenoviral vector containing the Escherichia coli beta-galactosidase (beta-Gal; lacZ) transgene (H5.010CBlacZ) resulted in a high level of transgene expression (64 +/- 6% of pancreatic cells expressed beta-Gal) at 3 days following infection. However, amylase levels in four of five different subcellular pancreatic fractions were significantly decreased at this time point. Direct pancreatic injection with either saline or psoralen/UV-inactivated adenovirus did not have this effect, whereas both transduction with an adenoviral vector containing a different transgene and transduction with a homologous transgene resulted in decreased pancreatic amylase. The decrease in subcellular amylase levels persisted at 7 days post-transduction, and then returned to baseline at 21 days post-transduction. There was associated histologic damage (increased edema, inflammation, cell destruction, and vacuolization) at 3 and 7 days post-transduction, which resolved by 21 days. In summary, adenoviral transduction of the pancreas results in increased viral transgene expression and a uniform decrease in host amylase production throughout the pancreas. The normalization of amylase levels and histology suggest that organ recovery occurs. Gene transfer technology as a novel strategy for pancreatic diseases such as diabetes, pancreatitis, and cystic fibrosis is feasible but will benefit from continued approaches to limit toxicity.

Bile-pancreatic juice replacement not cholinergic- and cholecystokinin-receptor blockade reverses acinar cell hyperstimulation after bile-pancreatic duct ligation

BACKGROUND

Acinar cell inhibitors (eg, atropine) fail to ameliorate clinical and experimental acute pancreatitis. We hypothesized that amelioration of pancreatic acinar cell hyperstimulation after bile and pancreatic duct ligation is better with gut replacement of bile and pancreatic juice than with cholinergic- and cholecystokinin (CCK)-receptor blockade.

METHODS

Using acinar cell amylase activity as an index of hyperstimulation, we studied 63 rats in two sets of experiments. Bile-pancreatic juice exclusion from gut--without (set one) and with (set two) bile and pancreatic duct obstruction--was treated with atropine and CCK-receptor antagonist L-364,718, or with enteral replacement of bile-pancreatic juice.

RESULTS

In the set one experiment, acinar cell hyperstimulation after bile-pancreatic juice exclusion was reversed by combined L-364,718 and atropine pretreatment. In set two, acinar cell hyperstimulation after bile and pancreatic duct ligation was reversed by enteral bile and pancreatic juice replacement, but not by combined L-364,718 and atropine pretreatment.

CONCLUSIONS

According to this experimental corollary of early gallstone impaction, prevention of acinar cell hyperstimulation after duct occlusion should be aimed at the source of the response to bile-pancreatic juice exclusion, namely, the gut, rather than at the target of the response, the pancreatic acinar cell.