Efficacy and safety of long-term indwelling plastic stents after resolution of pancreatic fluid collections with endoscopic transmural drainage: a systematic review and meta-analysis

BACKGROUND

Pancreatic fluid collections (PFCs) may recur after resolution with endoscopic transmural drainage (ETD) and standard stent removal (SSR). Herein, we compared the efficacy and safety of leaving long-term indwelling plastic stents (LTIS) vs. standard stent removal after PFC resolution with ETD.

METHODS

We performed a systematic review of MEDLINE, EMBASE, CINAHL, Scopus, and Cochrane databases from inception to September 2022. Full-text articles comparing long-term (> 6 months) outcomes of LTIS and SSR were eligible, as well as single-arm studies with ≥ 10 patients with LTIS. Two independent reviewers selected studies, extracted data, and assessed the risk of bias using the Newcastle-Ottawa Scale. Measured outcomes included the following: (A) PFC recurrence; (B) interventions for PFC recurrence; (C) technical success; and (D) adverse events (AEs). Meta-analysis was carried out using random-effects models.

RESULTS

We included 16 studies, encompassing 1285 patients. Compared to SSR after PFC resolution with ETD, LTIS was associated with significantly lower risk of PFC recurrence (3% vs. 23%; OR 0.22 [95%CI 0.09-0.52]; I2 = 45%) and need for interventions (2% vs. 14%; OR 0.35 [95%CI 0.16-0.78]; I2 = 0%). The superiority of LTIS on reducing PFC recurrence was found with walled-off necrosis, with or without disconnected pancreatic duct, and with placement of ≥ 2 LTIS. When using LTIS, the pooled proportion of AEs was 8% (95%CI 4-11%) and technical success was 93% (95%CI 86-99%).

CONCLUSIONS

Our results show that LTIS after PFC resolution with ETD is feasible, safe, and superior to SSR in reducing the risk of PFC recurrence and need for interventions.

Recent advances in understanding and managing acute pancreatitis

This review highlights advances made in recent years in the diagnosis and management of acute pancreatitis (AP). We focus on epidemiological, clinical, and management aspects of AP. Additionally, we discuss the role of using risk stratification tools to guide clinical decision making. The majority of patients suffer from mild AP, and only a subset develop moderately severe AP, defined as a pancreatic local complication, or severe AP, defined as persistent organ failure. In mild AP, management typically involves diagnostic evaluation and supportive care resulting usually in a short hospital length of stay (LOS). In severe AP, a multidisciplinary approach is warranted to minimize morbidity and mortality over the course of a protracted hospital LOS. Based on evidence from guideline recommendations, we discuss five treatment interventions, including intravenous fluid resuscitation, feeding, prophylactic antibiotics, probiotics, and timing of endoscopic retrograde cholangiopancreatography (ERCP) in acute biliary pancreatitis. This review also highlights the importance of preventive interventions to reduce hospital readmission or prevent pancreatitis, including alcohol and smoking cessation, same-admission cholecystectomy for acute biliary pancreatitis, and chemoprevention and fluid administration for post-ERCP pancreatitis. Our review aims to consolidate guideline recommendations and high-quality studies published in recent years to guide the management of AP and highlight areas in need of research.

Recent advances in understanding and managing acute pancreatitis

This review highlights advances made in recent years in the diagnosis and management of acute pancreatitis (AP). We focus on epidemiological, clinical, and management aspects of AP. Additionally, we discuss the role of using risk stratification tools to guide clinical decision making. The majority of patients suffer from mild AP, and only a subset develop moderately severe AP, defined as a pancreatic local complication, or severe AP, defined as persistent organ failure. In mild AP, management typically involves diagnostic evaluation and supportive care resulting usually in a short hospital length of stay (LOS). In severe AP, a multidisciplinary approach is warranted to minimize morbidity and mortality over the course of a protracted hospital LOS. Based on evidence from guideline recommendations, we discuss five treatment interventions, including intravenous fluid resuscitation, feeding, prophylactic antibiotics, probiotics, and timing of endoscopic retrograde cholangiopancreatography (ERCP) in acute biliary pancreatitis. This review also highlights the importance of preventive interventions to reduce hospital readmission or prevent pancreatitis, including alcohol and smoking cessation, same-admission cholecystectomy for acute biliary pancreatitis, and chemoprevention and fluid administration for post-ERCP pancreatitis. Our review aims to consolidate guideline recommendations and high-quality studies published in recent years to guide the management of AP and highlight areas in need of research.

Chronic Pancreatitis: Landmark Papers, Management Decisions, and Future

On May 16, 2015 at the invitation of the American Gastroenterological Association Institute Council E.P.D. presented a state-of-the-art lecture at Digestive Disease Week 2015. The aims were to discuss a selection of landmark papers in chronic pancreatitis (CP) that influence modern management and to conclude by suggesting some future directions. This is based on that presentation. We will specifically review the following: duct anatomy and pancreas divisum, description of chronic relapsing pancreatitis and its differentiation from recurrent acute pancreatitis and established CP (ECP), natural histories and gene discoveries of alcoholic, idiopathic and hereditary pancreatitis, development of pancreatic cancer in CP, exocrine pancreatic insufficiency and calculation of dose and delivery of enzymes, endoscopic ultrasonography, and autoimmune pancreatitis. With some exceptions, we exclude basic science and surgery.

Clinical update on fluid therapy and nutritional support in acute pancreatitis

BACKGROUND/OBJECTIVES

The aim of this focused review is to provide a valuable and updated source of information for clinical practice on fluid therapy (FT) and nutritional support in acute pancreatitis (AP).

METHODS

The review encompasses important new clinical information that has become available for understanding and offering these specific treatments since the 2013 publication of two guidelines, both the joint International Association of Pancreatology and American Pancreatic Association and the American College of Gastroenterology. The 2015 Revised Japanese Guideline is discussed selectively. To this end, the review is divided into 7 sections, including timing and cause of mortality; severity classification systems; predicting severity; response to treatment; nutritional support; fluid therapy and steps for further research.

CONCLUSIONS

In mild AP, begin oral feeding when nausea, vomiting and abdominal pain are improving. In (predicted) severe AP, feeding decisions should commence by 72 h, offering oral feeding if GI symptoms improve or enteral feeding if patients are symptomatic and/or intolerant to orals. All patients should be offered goal-directed FT during the first 6-12 h of presentation. Cautious FT is advised in those age >55 years or with preexisting organ failure or predictors of developing fluid sequestration.

Chronic pancreatitis

PURPOSE OF REVIEW

We review selected important clinical observations reported in 2012.

RECENT FINDINGS

Celiac disease is a risk factor for pancreatitis. Patients with recurrent acute pancreatitis likely have chronic pancreatitis, do not benefit from pancreatic sphincterotomy, and may not benefit from biliary sphincterotomy. Analysis of endoscopic ultrasonography (EUS) images with an artificial neural network (ANN) program may improve chronic pancreatitis diagnosis compared with clinical interpretation of images. In a multicenter, randomized controlled trial of chronic pancreatitis patients, 90 000 USP U of pancreatin with meals decreased fat malabsorption compared with placebo. Detection of visceral pain in chronic pancreatitis predicts pain relief from various treatments, but nonvisceral pain due to altered central pain processing may respond to agents such as pregabalin. Predictors of surgical pain relief include onset of symptoms less than 3 years and preoperatively no opioid use and less than five endoscopic procedures. Total pancreatectomy for presumed painful chronic pancreatitis remains controversial.

SUMMARY

Celiacs are at risk for pancreatitis. The diagnosis of chronic pancreatitis may be enhanced by ANN analysis of EUS imaging. Treatment of fat malabsorption requires 90,000 USP U of lipase with meals. Relief of pain from organ directed treatment of chronic pancreatitis may depend upon timing of interventions and whether pain is visceral or nonvisceral.

Pancreas divisum does not cause pancreatitis, but associates with CFTR mutations

Bertin et al. partially dispel arguments that pancreas divisum (PD) causes pancreatitis, but fascinatingly indicate that PD associates with CFTR gene mutations predisposing to pancreatitis. This association, however, does not definitely confer a pathophysiological role for PD in pancreatitis but may denote that PD co-mingles with CFTR mutations without influencing pancreatitis or CFTR mutations influence pancreatic duct embryogenesis. We advise "idiopathic pancreatitis" patients with PD to undergo genetic testing. In lieu of CFTR mutations undertake no endoscopic/surgical procedure; if CFTR mutations are found, then refer patients for genetic counseling and withhold endoscopic/surgical therapy unless randomized studies show benefit.

Chronic pancreatitis

PURPOSE OF REVIEW

We review important new clinical observations in chronic pancreatitis made in the past year.

RECENT FINDINGS

Tropical pancreatitis associates with SPINK1 and/or CFTR gene mutations in approximately 50% of patients, similar to the frequency in idiopathic chronic pancreatitis. Corticosteroids increase secretin-stimulated pancreatic bicarbonate concentrations in autoimmune pancreatitis (AIP) by restoring mislocalized CFTR protein to the apical ductal membrane. Most patients with asymptomatic hyperenzymemia have pancreatic lesions of unclear significance or no pancreatic lesions. Common pitfalls in the use of diagnostic tests for exocrine pancreatic insufficiency (EPI) confound interpretation of findings in irritable bowel syndrome and severe renal insufficiency. Further study is needed to improve the accuracy of endoscopic ultrasonography (EUS) to diagnose chronic pancreatitis. Celiac plexus block provides short-term pain relief in a subset of patients.

SUMMARY

Results of this year's investigations further elucidated the genetic associations of tropical pancreatitis, a reversible mislocalization of ductal CFTR in AIP, the association of asymptomatic pancreatic hyperenzymemia with pancreatic disorders, limitations of diagnostic tests for EPI, diagnosis of chronic pancreatitis by EUS and endoscopic pancreatic function testing and treatment of pain.

Pancreas divisum

We review important new clinical observations in pancreas divisum (PD) made since 2007. PD is common and has the same prevalence in the general population and idiopathic pancreatitis (IP). Up to 53% of patients with PD and IP have underlying idiopathic chronic pancreatitis (CP), and in rigorous prospective clinical follow-up and/or natural history studies, many with idiopathic recurrent acute pancreatitis (IRAP) have idiopathic CP. According to retrospective studies, PD does not modify the natural course of nonalcoholic or alcoholic CP. CFTR and/or SPINK1 gene mutations associate with IP (idiopathic CP and IRAP) independently of the presence of PD. More than one third of patients with pancreatitis or presumed pancreaticobiliary pain respond to placebo. Authors of uncontrolled studies report a significant symptomatic response to surgery and endotherapy in patients with IP and PD, but the response remains unproven and is largely limited to those with IRAP and not idiopathic CP or chronic pain.

Listeria monocytogenes exploits cystic fibrosis transmembrane conductance regulator (CFTR) to escape the phagosome

Virulence of the intracellular pathogen Listeria monocytogenes (Listeria) requires escape from the phagosome into the host cytosol, where the bacteria replicate. Phagosomal escape is a multistep process characterized by perforation, which is dependent on the pore-forming toxin listeriolysin O (LLO), followed by rupture. The contribution of host factors to Listeria phagosomal escape is incompletely defined. Here we show that the cystic fibrosis transmembrane conductance regulator (CFTR) facilitates Listeria cytosolic entry. CFTR inhibition or mutation suppressed Listeria vacuolar escape in culture, and inhibition of CFTR in wild-type mice before oral inoculation of Listeria markedly decreased systemic infection. We provide evidence that high chloride concentrations may facilitate Listeria vacuolar escape by enhancing LLO oligomerization and lytic activity. We propose that CFTR transiently increases phagosomal chloride concentration after infection, potentiating LLO pore formation and vacuole lysis. Our studies suggest that Listeria exploits mechanisms of cellular ion homeostasis to escape the phagosome and emphasize host ion-channel function as a key parameter of bacterial virulence.

Inhibition of acinar apoptosis occurs during acute pancreatitis in the human homologue DeltaF508 cystic fibrosis mouse

Previously, we found that the University of North Carolina cystic fibrosis (UNC-CF) mouse had more severe experimental acute pancreatitis (AP) than wild-type (WT) mice characterized by exuberant pancreatic inflammation and impaired acinar apoptosis. Because exon 10 CFTR gene mutations exhibit different phenotypes in tissues such as the mouse lung, we tested the hypothesis that DeltaF508-CF mice also develop severe AP associated with an antiapoptotic acinar phenotype, which requires indirect effects of the extracellular milieu. We used cerulein hyperstimulation models of AP. More severe pancreatitis occurred in cerulein-injected DeltaF508-CF vs. WT mice based on histological severity (P < 0.01) and greater neutrophil sequestration [P < 0.0001; confirmed by myeloperoxidase activity (P < 0.005)]. In dispersed acini cerulein-evoked necrosis was greater in DeltaF508-CF acini compared with WT (P < 0.05) and in WT acini pretreated with CFTR(inh)-172 compared with vehicle (P < 0.05). Cerulein-injected DeltaF508-CF vs. WT mice had less apoptosis based on poly(ADP-ribose) polymerase (PARP) cleavage (P < 0.005), absent DNA laddering, and reduced terminal deoxynucleotidyltransferase biotin-dUTP nick end labeling (TUNEL) staining (P < 0.005). Unexpectedly, caspase-3 activation was greater in DeltaF508-CF vs. WT acini at baseline (P < 0.05) and during AP (P < 0.0001). Downstream, DeltaF508-CF pancreas overexpressed the X-linked inhibitor of apoptosis compared with WT (P < 0.005). In summary, the DeltaF508-CF mutation, similar to the UNC-CF "null" mutation, causes severe AP characterized by an exuberant inflammatory response and impaired acinar apoptosis. Enhanced acinar necrosis in DeltaF508-CF occurs independently of extracellular milieu and correlates with loss of CFTR-Cl conductance. Although both exon 10 models of CF inhibit acinar apoptosis execution, the DeltaF508-CF mouse differs by increasing apoptosis signaling. Impaired transduction of increased apoptosis signaling in DeltaF508-CF acini may be biologically relevant to the pathogenesis of AP associated with CFTR mutations.

Advances in managing acute pancreatitis

This review highlights advances in acute pancreatitis (AP) made in the past year. We focus on clinical aspects of AP - severe disease especially - and risk stratification tools to guide the clinical care of patients. Most patients with AP have mild disease that requires a diagnostic evaluation, self-limited supportive care, and a short hospital stay. In patients with potentially severe AP, it is important for clinicians to use available risk-stratifying tools to identify high-risk patients and initiate timely interventions such as aggressive fluid resuscitation, close monitoring, early initiation of enteral nutrition, and appropriate use of endoscopic retrograde cholangio-pancreatography. This approach decreases morbidity and possibly mortality and is supported by evidence drawn from recent clinical guidelines, historical literature, and the highest quality studies published in the last year.

Alcohol use and cigarette smoking as risk factors for post-endoscopic retrograde cholangiopancreatography pancreatitis

BACKGROUND & AIMS

Alcohol use and cigarette smoking are associated with various pancreatic diseases, but it is not known whether they associate with post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP). We performed a retrospective case-control study to determine if these activities increase the risk of PEP.

METHODS

We identified 7638 patients who had undergone ERCP in the University of Michigan Health System and applied exclusion criteria to identify 123 with PEP. We randomly selected 308 age- and sex-stratified controls (2.5-fold case sample); after applying exclusion criteria 248 remained. In a masked fashion, we collected data for alcohol use, cigarette smoking, and 5 internal control variables: suspected sphincter of Oddi dysfunction (SOD), pancreatic sphincterotomy, moderate/difficult cannulation, 2 or more pancreatic injections, and pancreatic stent placement.

RESULTS

The univariate model showed an increased frequency of PEP in current drinkers (P < .001), former drinkers (P < .001), and former smokers (P < .001), as well as patients who were suspected of having SOD (P < .001), had undergone pancreatic sphincterotomy (P < .001), had a moderate/difficult cannulation (P = .001), and/or had 2 or more pancreatic injections (P = .007). The frequency of PEP was reduced in current smokers (P < .001). The multivariate model showed that the only independent significant predictors of PEP were current drinking (odds ratio [OR], 4.70; 95% confidence interval [CI], 2.60-8.50; P < .0001), former cigarette smoking (OR, 3.29; 95% CI, 1.28-8.44; P < .013), suspected SOD (OR, 3.69; 95% CI, 1.94-7.02; P < .001), and pancreatic sphincterotomy (OR, 5.91; 95% CI, 2.04-17.14; P = .001).

CONCLUSIONS

Current alcohol use and potentially former cigarette smoking are new risk factors for PEP. It is important to consider these variables in designing PEP prevention trials.

Systematic review: pancreatic enzyme treatment of malabsorption associated with chronic pancreatitis

BACKGROUND

Pancreatic enzyme supplementation is standard treatment for malabsorption caused by chronic pancreatitis. The FDA recently required all manufacturers to submit New Drug Applications to continue to market these agents because published data demonstrated variation in formulation, bioavailability and shelf-life while providing limited data about efficacy and safety.

AIM

To review systematically the design and results of randomized, parallel-design trials of pancreatic enzyme supplements in chronic pancreatitis patients with steatorrhea.

METHODS

A computer-assisted search of MEDLINE and EMBASE was performed to identify relevant studies. Two authors performed duplicate data extraction on study design, improvement in coefficient of fat absorption (CFA), diarrhoea and adverse events using pre-specified forms. Agreement between investigators for data extraction was greater than 95%.

RESULTS

Of 619 articles found through literature searching, 20 potentially relevant articles were identified and four manuscripts met inclusion criteria. No studies performed head-to-head comparisons of different supplements. Enzyme supplementation is more likely to improve CFA compared with placebo, but fat malabsorption remained abnormal. Important differences in patient population, study endpoint, study design, pancreatic enzyme dosage and measurement of CFA were present across trials, which precluded comparison of different agents.

CONCLUSIONS

Enzyme supplementation improves CFA compared to placebo, but may not abolish steatorrhoea.

Nitric oxide pathways and evidence-based perturbations in acute pancreatitis

Nitric oxide (NO) is a gaseous neurotransmitter, a vasodilator and paracrine regulator. In the pancreas, NO regulates normal pancreatic exocrine secretion, endocrine pancreatic insulin secretion and pancreatic microvascular blood flow. NO has multiple species and is produced de novo by 3 NO synthase enzymes. Endothelial NO synthase reduces the severity of the initial phase of experimental acute pancreatitis (AP). Cigarette smoking and chronic alcohol use disrupt normal NO pathways and are associated with pancreatitis and pancreatic cancer. The aims of this minireview are to describe normal intrapancreatic NO pathways, perturbations during experimental AP and due to epidemiological factors associated with pancreatic pathology, and the clinical implications of NO on AP.

New advances in acute pancreatitis

PURPOSE OF REVIEW

We endeavor to review important new advances in acute pancreatitis made in the past year. We focused on clinical aspects of acute pancreatitis, which contained new observations or insights into new or old concepts. For experimental acute pancreatitis we refer readers to a recent comprehensive review.

RECENT FINDINGS

Recently, case fatality rates of acute pancreatitis have stabilized; carbohydrate-deficient transferrin was shown to predict alcoholic acute pancreatitis; idiopathic chronic pancreatitis or occult cholelithiasis have been associated with 'recurrent acute pancreatitis' in most patients; and cystic fibrosis transmembrane conductance regulator genetic mutations were frequently found (10-50%) in patients with recurrent acute pancreatitis. In addition, alcohol was shown to increase the risk of pancreatic necrosis regardless of the cause of acute pancreatitis. Persistent organ failure and multiple organ dysfunction syndrome but not necessarily extent of necrosis were demonstrated to predict increased mortality in acute pancreatitis. Chemoprevention of post-endoscopic retrograde cholangiopancreatography acute pancreatitis remains unproven. Enteral feeding has been strongly recommended in severe acute pancreatitis. Finally, data are lacking for routine, prophylactic antibiotic administration to all patients with pancreatic necrosis.

SUMMARY

We reviewed studies this past year that further characterize the epidemiology, etiology and risk stratification of acute pancreatitis. Evolving areas include chemoprevention of post-endoscopic retrograde cholangiopancreatography acute pancreatitis and enteral feeding and antibiotics in severe acute pancreatitis. We await translation of novel therapies from the bench to bedside.

Pioglitazone reverses insulin resistance and impaired CCK-stimulated pancreatic secretion in eNOS(-/-) mice: therapy for exocrine pancreatic disorders?

In mice, eNOS (endothelial nitric oxide synthase) maintains in vivo pancreatic secretory responses to carbachol or cholecystokinin octapeptide (CCK-8), maintains insulin sensitivity, and modulates pancreatic microvascular blood flow (PMBF). eNOS(-/-) mice are insulin resistant, and their exocrine pancreatic secretion is impaired. We hypothesized that the reduced exocrine pancreatic secretion in eNOS(-/-) mice is due to insulin resistance or impaired PMBF. To test this hypothesis, we gave eNOS(-/-) and wild-type (WT) mice pioglitazone (20 or 50 mg.kg(-1).day(-1)), an insulin-sensitizing peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activator, and measured pancreatic protein secretion evoked by CCK-8 (160 pmol.kg(-1).h(-1), a maximal stimulus). We also measured insulin resistance, serum glucose, C-peptide, insulin, pancreatic RNA digestive enzyme expression, and PMBF (microsphere technique). In WT mice, pioglitazone did not increase CCK-8-stimulated protein output over baseline. In eNOS(-/-) mice, however, pioglitazone substantially increased the low CCK-8-stimulated protein output that is characteristic of these mutant mice (P < 0.005). Pioglitazone abolished the CCK-8-evoked hyperinsulinemia (P < 0.005) and increased insulin sensitivity of eNOS(-/-) mice (P < 0.05), the latter based on hyperinsulinemic-euglycemic clamp studies. Pioglitazone had no effect on PMBF or pancreas mRNA expression of insulin or digestive enzymes. We conclude that in hyperinsulinemic eNOS(-/-) mice, a nonobese model of insulin resistance relevant to diabetes mellitus and possibly chronic pancreatitis, reduced pancreatic secretion is caused, at least in part, by insulin resistance. Insulin-sensitizing PPAR-gamma agonists such as pioglitazone may thus simultaneously correct endocrine and exocrine pancreatic disorders.

Chronic pancreatitis

PURPOSE OF REVIEW

As in our previous reviews, we endeavor to review important new observations in chronic pancreatitis made in the past year. Topics recently reviewed were truncated to accommodate a surge in publications on clinical aspects of chronic pancreatitis, which contained new observations or insights into new or old concepts.

RECENT FINDINGS

Cystic fibrosis carriers have been found to be at increased risk of pancreatitis. Autoimmune pancreatitis may belong to a multiorgan immunoglobulin G4-related autoimmune disease, and the natural history of chronic pancreatitis differs among the etiologies. Diffusion-weighted magnetic resonance imaging improves upon previous methodologies for diagnosing reduced pancreatic exocrine secretion, and fecal elastase-1 has been found to be a poor test for diagnosing pancreatic malabsorption. Visceral hyperalgesia or heightened central pain perception may contribute to pain in chronic pancreatitis. Instruments are evolving to assess quality of life in chronic pancreatitis, and fibrolytic agents have been found to have therapeutic promise.

SUMMARY

Researchers this past year have further characterized genetic, molecular and clinical aspects of chronic pancreatitis. Advancing the understanding of fibrogenesis, mechanisms of exocrine insufficiency, calcification, and pain and continuing development/modification of diagnostic tests should lead to improved prevention, detection and treatment of the condition. More accurate quantification of outcomes is critical for translating potential therapies from bench to bedside.

Chronic pancreatitis

PURPOSE OF REVIEW

As in our previous reviews, we endeavor to review important new observations in chronic pancreatitis made in the past year. We included articles, including review articles, only if they contained new observations or readdressed old questions and provided new insights into old and new concepts.

RECENT FINDINGS

Important observations include the following: (1) Strong association between cystic fibrosis transmembrane regulator dysfunction/mutations and 'recurrent acute pancreatitis', particularly in patients with pancreas divisum (2) Pancreas divisum may be incidental finding in recurrent acute pancreatitis (3) Smoking increases risk of chronic pancreatitis (4) Coxsackie B virus may increase severity of alcoholic chronic pancreatitis (5) CD4+ T cells and an immune reaction against amylase may play a role in pathogenesis of autoimmune pancreatitis (6) 2-(18F)-Fluro-2-deoxy-D-glucose positron emission tomography might be useful to detect pancreatic cancer in chronic pancreatitis patients at risk for developing pancreatic cancer, but contrast-enhanced Doppler ultrasound or endosonography may be as sensitive and better than contrast enhanced computed tomography (7) Superiority of surgery vs endotherapy for long term pain relief and weight gain in painful chronic pancreatitis (8) Early treatment of pain and malabsorption may improve life quality (9) Antifibrogenesis and fibrolytic agents as potential therapies.

SUMMARY

Ongoing basic and clinical research this past year has further characterized genetic, molecular and clinical aspects of chronic pancreatitis. The advent of predictable and lasting treatments of chronic pancreatitis is most likely to appear on the wings of carefully conducted studies targeting genetic and molecular mechanisms of chronic pancreatitis, particularly pancreatic fibrogenesis.

Massive lower gastrointestinal bleeding after rejection of pancreatic transplants

BACKGROUND

This article highlights two cases of massive lower gastrointestinal bleeding in patients on dialysis after rejection of kidney-pancreas transplants. Patient 1 was a 34-year-old female with 27 years of type I diabetes, who had a kidney-pancreas transplant in 1996, which was complicated by rejection of the kidney and pancreas in 2000 and 2002, respectively. Later in 2002, she presented in shock after experiencing cramping abdominal pain and passage of large bloody stools. Patient 2 was a 38-year-old male with 26 years of type I diabetes, who had a pancreas-kidney transplant in 1998, which was complicated by rejection of the kidney and pancreas in early 2003. He presented in late 2003 with a single episode of coffee-ground emesis and two episodes of brisk hematochezia.

INVESTIGATION

Arterial angiography.

DIAGNOSIS

Pseudoaneurysm and small-bowel fistula from the arterial supply to the transplanted pancreas.

MANAGEMENT

Angiographic embolization of the aneurysmal vessel and fistula achieved hemostasis. Patient 1 did not have her transplanted organ surgically removed and suffered a recurrent massive lower gastrointestinal bleed that proved fatal. In Patient 2, subsequent surgery and removal of the rejected pancreas was performed and the patient continues to do well.

Chronic pancreatitis

PURPOSE OF REVIEW

Clinicians are learning more about chronic pancreatitis but are entering an era of some confusion, primarily driven by uncovering new etiologies of chronic pancreatitis. Ideally, this knowledge will lead to better diagnosis and treatment, and abandonment of ill-conceived treatments. In contrast with previous reviews, this review highlights select contributions this year that may develop into true advances in chronic pancreatitis.

RECENT FINDINGS

Small steps have been made to understand better the molecular basis of chronic pancreatitis. Diagnosis of early chronic pancreatitis remains challenging. Rapid diagnosis by combining endoscopy and a direct stimulatory test of pancreatic function may lead to more widespread use of function testing, but this test is not ready for clinical use. Application of microarray and proteomic technologies may aid future diagnosis of chronic pancreatitis. The failure to account clearly for the phenotype of patients with chronic pancreatitis may confound delineating the etiologies of chronic pancreatitis. Clinical description and studies of autoimmune pancreatitis have led to the realization that steroids are an effective treatment for this form of chronic pancreatitis. Genetic-based studies have provided insight into the pathogenic mechanisms of chronic pancreatitis. Investigation of the role of stellate cells, an essential component fibrogenesis, has led to identification of potential novel treatments for chronic pancreatitis.

SUMMARY

Ongoing basic and clinical research this past year has characterized further the histologic, genetic, molecular, and clinical aspects of chronic pancreatitis, efforts that may translate into novel therapies once well-designed, controlled studies have been performed.

Endothelial nitric oxide synthase is protective in the initiation of caerulein-induced acute pancreatitis in mice

The effect of inhibiting nitric oxide (NO) synthase (NOS) or enhancing NO on the course of acute pancreatitis (AP) is controversial, in part because three NOS isoforms exist: neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). We investigated whether inhibition or selective gene deletion of NOS isoforms modified the initiation phase of caerulein-induced AP in mice and explored whether this affected pancreatic microvascular blood flow (PMBF). We investigated the effects of nonspecific NOS inhibition with N(omega)-nitro-l-arginine (l-NNA; 10 mg/kg ip) or targeted deletion of eNOS, nNOS, or iNOS genes on the initiation phase of caerulein-induced AP in mice using in vivo and in vitro models. Western blot analysis was performed to assess eNOS phosphorylation status, an indicator of enzyme activity, and microsphere studies were used to measure PMBF. l-NNA and eNOS deletion, but not nNOS or iNOS deletion, increased pancreatic trypsin activity and serum lipase during the initiation phase of in vivo caerulein-induced AP. l-NNA and eNOS did not affect trypsin activity in caerulein-hyperstimulated isolated acini, suggesting that nonacinar events mediate the effect of NOS blockade in vivo. The initiation phase of AP in wild-type mice was associated with eNOS Thr(495) residue dephosphorylation, which accompanies eNOS activation, and a 178% increase in PMBF; these effects were absent in eNOS-deleted mice. Thus eNOS is the main isoform influencing the initiation of caerulein-induced AP. eNOS-derived NO exerts a protective effect through actions on nonacinar cell types, most likely endothelial cells, to produce greater PMBF.

Secretagogue-stimulated pancreatic secretion is differentially regulated by constitutive NOS isoforms in mice

Nitric oxide (NO) and NO synthase (NOS) play controversial roles in pancreatic secretion. NOS inhibition reduces CCK-stimulated in vivo pancreatic secretion, but it is unclear which NOS isoform is responsible, because NOS inhibitors lack specificity and three NOS isoforms exist: neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). Mice having individual NOS gene deletions were used to clarify the NOS species and cellular interactions influencing pancreatic secretion. In vivo secretion was performed in anesthetized mice by collecting extraduodenal pancreatic duct juice and measuring protein output. Nonselective NOS blockade was induced with N(omega)-nitro-L-arginine (L-NNA; 10 mg/kg). In vivo pancreatic secretion was maximal at 160 pmol.kg(-1).h(-1) CCK octapeptide (CCK-8) and was reduced by NOS blockade (45%) and eNOS deletion (44%). Secretion was unaffected by iNOS deletion but was increased by nNOS deletion (91%). To determine whether the influence of NOS on secretion involved nonacinar events, in vitro CCK-8-stimulated secretion of amylase from isolated acini was studied and found to be unaltered by NOS blockade and eNOS deletion. Influence of NOS on in vivo secretion was further examined with carbachol. Protein secretion, which was maximal at 100 nmol.kg(-1).h(-1) carbachol, was reduced by NOS blockade and eNOS deletion but unaffected by nNOS deletion. NOS blockade by L-NNA had no effect on carbachol-stimulated amylase secretion in vitro. Thus constitutive NOS isoforms can exert opposite effects on in vivo pancreatic secretion. eNOS likely plays a dominant role, because eNOS deletion mimics NOS blockade by inhibiting CCK-8 and carbachol-stimulated secretion, whereas nNOS deletion augments CCK-8 but not carbachol-stimulated secretion.

Chronic pancreatitis

PURPOSE OF REVIEW

We are beginning to better understand the causes of chronic pancreatitis. This knowledge will hopefully lead to better diagnosis and treatment and abandonment of ill-conceived treatments. This review highlights contributions that moved the field toward these goals in the past year.

RECENT FINDINGS

Small steps have been made toward a better understanding of the molecular basis, particularly genetic causes, of the forms of chronic pancreatitis. Investigation of the role of stellate cells, an essential component of the fibrosis of chronic pancreatitis, has led to the finding that lovastatin inhibits stellate cell activation and could surface as a novel treatment of chronic pancreatitis. The clinical description of autoimmune pancreatitis has led to the realization that steroids are effective treatment for this form of chronic pancreatitis. Other treatments such as extracorporeal shock wave lithotripsy and endoscopic treatments have not been proved, because no controlled studies support these treatments over other treatments. The diagnosis of chronic pancreatitis may be enhanced by the new imaging technique of electronic pancreatoscopy whereby a 2.1-mm diameter scope can be advanced into the pancreatic duct through a duodenoscope. However, the data are too preliminary at this time to advocate this imaging procedure. A potential new endoscopic pancreatic function test may lead to more widespread use of function testing, but this test is not perfected and also cannot be advised for use at present.

SUMMARY

Ongoing basic and clinical research this past year has further characterized the genetic, molecular, and clinical aspects of chronic pancreatitis: efforts that may translate into novel therapies, once well-designed, controlled studies have been performed.

Caerulein-induced acute pancreatitis inhibits protein synthesis through effects on eIF2B and eIF4F

Acute pancreatitis (AP) has been shown in some studies to inhibit total protein synthesis in the pancreas, whereas in other studies, protein synthesis was not affected. Previous in vitro work has shown that high concentrations of cholecystokinin both inhibit protein synthesis and inhibit the activity of the guanine nucleotide exchange factor eukaryotic initiation factor (eIF)2B by increasing the phosphorylation of eIF2alpha. We therefore evaluated in C57BL/6 mice the effects of caerulein-induced AP on pancreatic protein synthesis, eIF2B activity and other protein translation regulatory mechanisms. Repetitive hourly injections of caerulein were administered at 50 microg/kg ip. Pancreatic protein synthesis was reduced 10 min after the initial caerulein administration and was further inhibited after three and five hourly injections. Caerulein inhibited the two major regulatory points of translation initiation: the activity of the guanine nucleotide exchange factor eIF2B (with an increase of eIF2alpha phosphorylation) and the formation of the eIF4F complex due, in part, to degradation of eIF4G. This inhibition was not accounted for by changes in the upstream stimulatory pathway, because caerulein activated Akt as well as phosphorylating the downstream effectors of mTOR, 4E-BP1, and ribosomal protein S6. Caerulein also decreased the phosphorylation of the eukaryotic elongation factor 2, implying that this translation factor was not inhibited in AP. Thus the inhibition of pancreatic protein synthesis in this model of AP most likely results from the inhibition of translation initiation as a result of increased eIF2alpha phosphorylation, reduction of eIF2B activity, and the inhibition of eIF4F complex formation.