Role of nitric oxide derived from alveolar macrophages in the early phase of acute pancreatitis

Pulmonary complications of acute pancreatitis

Introduction: Acute pancreatitis is an inflammatory condition of the pancreas, which runs a severe course in 20% of patients, wherein it is associated with high mortality. It is associated with several pleuro-pulmonary complications with variable severity that may occur either in isolation but are frequently present in combination. Clinicians need to be aware of these complications for early and appropriate management.Areas covered: We performed a systematic search of the PUBMED database (1970-2019) to identify relevant articles focusing on pleuro-pulmonary complications that may occur in patients with acute pancreatitis. We also retrieved articles describing the pathophysiological mechanisms and treatment approach of the various complications.Expert opinion: Acute pancreatitis is usually a self-limiting disease, but the development of organ failure during the course worsens the clinical outcome. Pulmonary complications usually occur early in the course of acute pancreatitis. Clinicians need to recognize the various pulmonary complications of acute pancreatitis, early during the disease, and manage them appropriately and aggressively to improve outcomes.

Ischemic Preconditioning Preserves Liver Energy Charge and Function on Hepatic Ischemia/Reperfusion Injury in Rats

BACKGROUND

Cell energy during ischemia/reperfusion depends on mechanisms including adenosine diphosphate degradation, oxygen species and cytokine liberation, neutrophil infiltration, and endothelial dysfunction. Preconditioning-a brief ischemic episode that confers a state of protection against subsequent ischemia-reperfusion injury-involves NO and adenosine production, reduction in oxygen species liberation, and preservation of microcirculation. During hypoxia, constitutive NO production assures adequate oxygen delivery and reduced energy loss. The aim was to determine the role of ischemic preconditioning in the stimulation of constitutive endothelial nitric oxide (NO) production and its effect on energy charge, radical oxygen species generation, cytokine liberation, and neutrophil infiltration during reperfusion.

MATERIALS AND METHODS

Rats were assigned to one of four groups depending on the preconditioning protocol: hepatic ischemia/reperfusion, or hepatic ischemia/reperfusion and ischemic preconditioning, for 5, 10, or 20 min. A portosystemic shunt was established between the portal and left jugular veins during ischemia.

RESULTS

Preconditioning produced rises in plasma nitrites, but no rise in inducible nitric oxide synthase gene expression. A 5 or 10 min preconditioning period allowed for higher energy charge, bile production, and glutathione levels, with less lipoperoxide, alanine aminotransferase, tumor necrosis factor-α, and interleukin-1 production and neutrophil infiltration, compared with 20 min or control. Survival was 80% in the G10 group, 70 in G5, 10 in GC, and 0% in the G20 group.

CONCLUSIONS

Ten-min liver preconditioning improves survival and prevents energy loss during hepatic ischemia/reperfusion by stimulating constitutive NO production, maintaining glutathione concentrations and reducing oxygen species and proinflammatory cytokine generation as well as neutrophil infiltration.

Effects of Cytokines and Other Inflammatory Mediators on Human Acute Pancreatitis

Most episodes of acute pancreatitis are mild, but severe disease complicated by multiple system organ failure develops in up to 20% of cases. In all patients with pancreatitis, the accumulation of leukocytes in pancreatic and extrapancreatic tissue, and the release of various mediators from them and other sites are important determinants of disease severity. Proinflammatory mediators, whose initial job is to limit the local damage, are released early in the disease. However, these mediators can exacerbate the severity of the pancreatitis when they continue to be elaborated in greater amounts or for longer periods than normal. When their actions are blocked or their release is inhibited, the severity of experimental pancreatitis and its associated mortality rate are less. This suggests the possibility that agents that inhibit the release and/or action of these mediators could be beneficial clinically.

Reverse-migrated neutrophils regulated by JAM-C are involved in acute pancreatitis-associated lung injury

Junctional adhesion molecule-C (JAM-C) plays a key role in the promotion of the reverse transendothelial migration (rTEM) of neutrophils, which contributes to the dissemination of systemic inflammation and to secondary organ damage. During acute pancreatitis (AP), systemic inflammatory responses lead to distant organ damage and typically result in acute lung injury (ALI). Here, we investigated the role of rTEM neutrophils in AP-associated ALI and the molecular mechanisms by which JAM-C regulates neutrophil rTEM in this disorder. In this study, rTEM neutrophils were identified in the peripheral blood both in murine model of AP and human patients with AP, which elevated with increased severity of lung injury. Pancreatic JAM-C was downregulated during murine experimental pancreatitis, whose expression levels were inversely correlated with both increased neutrophil rTEM and severity of lung injury. Knockout of JAM-C resulted in more severe lung injury and systemic inflammation. Significantly greater numbers of rTEM neutrophils were present both in the circulation and pulmonary vascular washout in JAM-C knockout mice with AP. This study demonstrates that during AP, neutrophils that are recruited to the pancreas may migrate back into the circulation and then contribute to ALI. JAM-C downregulation may contribute to AP-associated ALI via promoting neutrophil rTEM.

The role of nitric oxide in the physiology and pathophysiology of the exocrine pancreas

SIGNIFICANCE

Nitric oxide (NO), a ubiquitous gaseous signaling molecule, contributes to both pancreatic physiology and pathophysiology.

RECENT ADVANCES

The present review provides a general overview of NO synthesis, signaling, and function. Further, it specifically discusses NO metabolism and its effects in the exocrine pancreas and focuses on the role of NO in the pathogenesis of acute pancreatitis and pancreatic ischemia/reperfusion injury.

CRITICAL ISSUES

Unfortunately, the role of NO in pancreatic physiology and pathophysiology remains controversial in numerous areas. Many questions regarding the messenger molecule still remain unanswered.

FUTURE DIRECTIONS

Probably the least is known about the downstream targets of NO, which need to be identified, especially at the molecular level.

Role of macrophages in the progression of acute pancreatitis

In addition to pancreatic cells, other inflammatory cell populations contribute to the generation of inflammatory mediators during acute pancreatitis. In particular, macrophages could be activated by mediators released during pancreatitis by a damaged pancreas. It has been reported that peritoneal macrophages, alveolar macrophages and Kupffer cells become activated in different stages of severe acute pancreatitis. However, macrophages display remarkable plasticity and can change their physiology in response to environmental cues. Depending on their microenvironmental stimulation, macrophages could follow different activation pathways resulting in marked phenotypic heterogeneity. This ability has made these cells interesting therapeutical targets and several approaches have been assayed to modulate the progression of inflammatory response secondary to acute pancreatitis. However, despite the recent advances in the modulation of macrophage function in vivo, the therapeutical applications of these strategies require a better understanding of the regulation of gene expression in these cells.

Essential role of monocytes and macrophages in the progression of acute pancreatitis

Acute pancreatitis (AP) is an inflammatory condition of the pancreas caused by an imbalance in factors involved in maintaining cellular homeostasis. Earliest events in AP occur within acinar cells accompanied by other principal contributors to the inflammatory response i.e. the endothelial cells, immunocytes (granulocytes, monocytes/macrophages, lymphocytes) and neutrophils. Monocytes/macrophages are important inflammatory mediators, involved in the pathophysiology of AP, known to reside in the peritoneal cavity (in the vicinity of the pancreas) and in peripancreatic tissue. Recent studies suggested that impaired clearance of injured acini by macrophages is associated with an altered cytokine reaction which may constitute a basis for progression of AP. This review focuses on the role of monocytes/macrophages in progression of AP and discusses findings on the inflammatory process involved.

A crucial role of nitric oxide in acute lung injury secondary to the acute necrotizing pancreatitis

To investigate the role of nitric oxide (NO) in acute lung inflammation and injury secondary to acute necrotizing pancreatitis (ANP), 5% sodium taurocholate was retrogradely injected into the biliopancreatic duct of rats to ANP model. These ANP rats were given L-Arginine (L-Arg, 100 mg/kg), L-NAME (10 mg/kg), or their combination by intraperitoneal injection 30 min prior to ANP induction. At 1, 3, 6, and 12 hours after ANP induction, lung NO production, and inducible NO synthase (iNOS) expression were measured. Lung histopathological changes, bronchoalveolar lavage (BAL) protein concentration, proinflammatory mediators tumor necrotic factor alpha (TNF-α), and lung tissue myeloperoxidase (MPO) activity were examined. Results showed that NO production and iNOS mRNA expression in alveolar macrophages (AMs) were significantly increased along with significant increases in lung histological abnormalities and BAL proteins in the ANP group, all of which were further enhanced by pretreatment with L-Arg and attenuated by pretreatment with L-NAME, respectively. These markers were slightly attenuated by pretreatment with combination of L-Arg + L-NAME, suggesting that NO is required for initiating the acute lung damage in ANP rats, and also that L-Arg-enhanced lung injury is mediated by its NO generation rather than its direct effect. MPO activity and TNF-α expression in lung were upregulated in the ANP rats and further enhanced by pretreatment with L-Arg and attenuated by pretreatment with L-NAME, respectively. These results suggest that overproduction of NO mediated by iNOS in the lung is required for the acute lung inflammation and damage secondary to ANP.

Alveolar macrophage inducible nitric oxide synthase-dependent pulmonary microvascular endothelial cell septic barrier dysfunction

Inducible nitric oxide (NO) synthase (iNOS) from neutrophils and alveolar macrophages (AM) contributes to the pathophysiology of murine septic acute lung injury (ALI). It is not known if AM iNOS has a direct effect on septic pulmonary microvascular endothelial cell (PMVEC) permeability. We hypothesized that AM iNOS mediates PMVEC permeability in vitro under septic conditions through NO and peroxynitrite. 100,000 confluent PMVEC on cell-culture inserts were co-incubated with iNOS+/+ vs. iNOS-/- AM, in various ratios of AM to PMVEC. PMVEC injury was assessed by trans-PMVEC Evans Blue-labelled albumin flux in the presence or absence of cytomix (equimolar TNF-alpha, IL-1beta and IFN-gamma). Cytomix stimulation dose-dependently increased trans-PMVEC EB-albumin flux, which was exaggerated (1.4+/-0.1% vs. 0.4+/-0.1% in unstimulated PMVEC, p<0.05) in the presence of iNOS+/+, but not iNOS-/-, AM in the upper compartment. Similarly, iNOS+/+, but not iNOS-/-, AM in the lower compartment also enhanced septic trans-PMVEC albumin leak. The mechanism of iNOS-dependent septic PMVEC permeability was pursued through pharmacologic studies with inhibitors of NOS, and scavengers of NO, superoxide, and peroxynitrite, and treatment of PMVEC with the NO donor, DETA-NONOate. Septic iNOS+/+ AM-dependent trans-PMVEC albumin leak was significantly attenuated by pharmacologic iNOS inhibition (L-NAME and 1400W), and scavenging of either NO (oxyhemoglobin), superoxide (PEG-SOD), or peroxynitrite (FeTPPS). Exogenous NO (DETA-NONOate) had no effect on PMVEC permeability. These data are consistent with a direct role of AM iNOS in septic PMVEC barrier dysfunction, which is likely mediated, in part, through peroxynitrite.

Molecular basis for susceptibility of plasma platelet-activating factor acetylhydrolase to oxidative inactivation

Platelet-activating factor acetylhydrolase (PAF-AH) is a phospholipase A2 that inactivates potent lipid messengers, such as PAF and modified phospholipids generated in settings of oxidant stress. The catalytic activity of PAF-AH is sensitive to oxidants, a feature that may have pathological consequences. We report that peroxynitrite, an oxidant species generated after cellular activation, mediates oxidative inactivation of PAF-AH. We found that peroxynitrite inactivated and derivatized the recombinant protein and obtained evidence supporting a role for a methionine and two tyrosine residues in this process. We employed interspecies comparisons and site-directed mutagenesis and identified a role for M-117, and a smaller contribution of Y-307 and Y-335 as targets of oxidant attack using free and lipoprotein-associated recombinant proteins. M-117 is adjacent to W-115 and L-116, which are essential for association of PAF-AH with LDL. Oxidation of LDL-associated PAF-AH partially dissociated the enzyme from the particles. Similarly, oxidation of the purified enzyme in the absence of lipoproteins prevented subsequent association with LDL. These results provide new insights into the molecular mechanisms that mediate inactivation of PAF-AH in settings of oxidant stress and the consequences of oxidation on the ability of this enzyme to associate with LDL.

Induction of Nitric Oxide Synthase is a Key Determinant of Progression to Pulmonary Injury in Experimental Pancreatitis

BACKGROUND

The immunomodulatory potential of nitric oxide provides prospective strategies to attenuate inappropriate inflammatory reactions. This study tested the hypothesis that inhibition of nitric oxide synthase (NOS) reduces end-organ injury in pancreatitis.

METHODS

Pancreatitis was induced in male Sprague-Dawley rats by intraperitoneal (i.p.) injection of 20% L-arginine (500 mg/100 g of body weight). Animals were randomized into four groups of 45: Pancreatitis without intervention; pre-treatment with i.p. aminoguanidine (AMG) (50 mg/kg), an isoform-specific inhibitor of inducible NOS; post-treatment with AMG (50 mg/kg); and controls. Pancreatic and pulmonary pathology, neutrophil infiltration (myeloperoxidase activity), endothelial permeability (bronchoalveolar lavage, wet:dry weight ratio), NOS expression, and concentrations of pro-inflammatory cytokines (tumor necrosis factor-alpha; interleukin-6) were assessed.

RESULTS

Inhibition of iNOS significantly reduced end-organ injury. Pancreatic and pulmonary injury scores were markedly attenuated in the AMG treatment groups compared with no intervention (p < 0.05). Increased endothelial permeability (2,411.1 +/- 47.9) and neutrophil sequestration (1.99 +/- 0.01) were manifest in the untreated animals compared with AMG pretreatment (1,286.8 +/- 35.1 and 1,548.0 +/- 0.1; p < 0.05). In addition, a significant reduction in inflammatory cytokine concentrations was observed (p < 0.05).

CONCLUSIONS

Inhibition of inducible NOS encourages a more benign immunologic profile, minimizing the deleterious effects of unrestrained neutrophil sequestration subsequent to pancreatitis.

Pathophysiology of pulmonary complications of acute pancreatitis

Acute pancreatitis in its severe form is complicated by multiple organ system dysfunction, most importantly by pulmonary complications which include hypoxia, acute respiratory distress syndrome, atelectasis, and pleural effusion. The pathogenesis of some of the above complications is attributed to the production of noxious cytokines. Clinically significant is the early onset of pleural effusion, which heralds a poor outcome of acute pancreatitis. The role of circulating trypsin, phospholipase A2, platelet activating factor, release of free fatty acids, chemoattractants such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, IL-6, IL-8, fMet-leu-phe (a bacterial wall product), nitric oxide, substance P, and macrophage inhibitor factor is currently studied. The hope is that future management of acute pancreatitis with a better understanding of the pathogenesis of lung injury will be directed against the production of noxious cytokines.

Effects of macrophage inducible nitric oxide synthase in murine septic lung injury

Inducible nitric oxide synthase (iNOS) contributes importantly to septic pulmonary protein leak in mice with septic acute lung injury (ALI). However, the role of alveolar macrophage (AM) iNOS in septic ALI is not known. Thus we assessed the specific effects of AM iNOS in murine septic ALI through selective AM depletion (via intratracheal instillation of clodronate liposomes) and subsequent AM reconstitution (via intratracheal instillation of donor iNOS+/+ or iNOS−/− AM). Sepsis was induced by cecal ligation and perforation, and ALI was assessed at 4 h: protein leak by the Evans blue (EB) dye method, neutrophil infiltration via myeloperoxidase (MPO) activity, and pulmonary iNOS mRNA expression via RT-PCR. In iNOS+/+ mice, AM depletion attenuated the sepsis-induced increases in pulmonary microvascular protein leak (0.3 ± 0.1 vs. 1.4 ± 0.1 μg EB·g lung−1·min−1; P < 0.05) and MPO activity (37 ± 4 vs. 67 ± 8 U/g lung; P < 0.05) compared with that shown in non-AM-depleted mice. In AM-depleted iNOS+/+ mice, septic pulmonary protein leak was restored by AM reconstitution with iNOS+/+ AM (0.9 ± 0.3 μg EB·g lung−1·min−1) but not with iNOS−/− donor AM. In iNOS−/− mice, sepsis did not induce pulmonary protein leak or iNOS mRNA expression, despite increased pulmonary MPO activity. However, AM depletion in iNOS−/− mice and subsequent reconstitution with iNOS+/+ donor AM resulted in significant sepsis-induced pulmonary protein leak and iNOS expression. Septic pulmonary MPO levels were similar in all AM-reconstituted groups. Thus septic pulmonary protein leak is absolutely dependent on the presence of functional AM and specifically on iNOS in AM. AM iNOS-dependent pulmonary protein leak was not mediated through changes in pulmonary neutrophil influx.

Local and systemic effects of hypertonic solution (NaCl 7.5%) in experimental acute pancreatitis

OBJECTIVES

Severe acute pancreatitis (AP) is characterized by hemodynamic alterations and a systemic inflammatory response, leading to a high mortality rate. Treatment of hemorrhagic shock with hypertonic saline solutions significantly reduces mortality through an improvement in the hemodynamic conditions and possibly by an anti-inflammatory effect. Therefore, hypertonic solutions could be effective in AP.

METHODS

Wistar rats were divided in 4 groups: group C, control, without AP; group NT, AP, without treatment; group NS, treatment with normal saline solution (NaCl 0.9%) 1 hour after AP; group HTS, treatment with hypertonic saline solution (NaCl 7.5%) 1 hour after AP. AP was induced by injection of 2.5% sodium taurocholate into the pancreatic duct. Mean arterial blood pressure (MAP) and heart rate were recorded at 0 and 2, 4, 24, and 48 hours after AP. After induction of AP, animals were killed at 2, 12, 24, and 48 hours for serum amylase, interleukin (IL)-6, and IL-10 analysis, pancreatic tissue culture and histologic analysis, oxidation and phosphorylation of liver mitochondria, pulmonary myeloperoxidase activity (MPO), and mortality study.

RESULTS

In animals of groups NS and NT, a significant decrease of MAP was observed 48 hours after AP (NS: 91 +/- 3 mm Hg; NT: 89 +/- 3 mm Hg) compared with baseline (C: 105 +/- 2 mm Hg) and to HTS group (HTS: 102 +/- 2 mm Hg; P < 0.05). In animals of group NT, NS, and HTS, serum IL-6 and IL-10 levels were significantly higher at 2 hours after AP compared with the control group. However, IL-6 levels at 12 hours after AP and IL-10 levels at 2 and 12 hours after AP were significant lower in group HTS compared with NS and NT groups (P < 0.05). In group HTS, a decrease of pulmonary MPO activity and of pancreatic infection was observed 24 hours after AP compared with NT and NS groups (P < 0.05). A significant reduction on pancreatic acinar necrosis and mitochondrial dysfunction was observed after 48 hours of AP in animals of group HTS compared with groups NT and NS (P < 0.05). A significant reduction on mortality was observed in HTS (0/14) compared with NS (6/17; 35%) and NT (7/20; 35%).

CONCLUSIONS

The administration of hypertonic saline solution in experimental AP attenuated hemodynamic alterations, decreased inflammatory cytokines, diminished systemic lesions and pancreatic acinar necrosis, prevented pancreatic infection, and reduced the mortality rate.

Oxidative stress and nitric oxide in rats with alcohol-induced acute pancreatitis

AIM: Oxygen free radical mediated tissue damage is well established in pathogenesis of acute pancreatitis (AP). Whether nitric oxide (NO) plays a deleterious or a protective role is unknown. In alcohol-induced AP, we studied NO, lipooxidative damage and glutathione in pancreas, lung and circulation.

METHODS: AP was induced in rats (n = 25) by injection of ethyl alcohol into the common biliary duct. A sham laparatomy was performed in controls (n = 15). After 24 h the animals were killed, blood and tissue sampling were done.

RESULTS: Histopathologic evidence confirmed the development of AP. Marked changes were observed in the pulmonary tissue. Compared with controls, the AP group displayed higher values for NO metabolites in pancreas and lungs, and thiobarbituric acid reactive substances in circulation. Glutathione was lower in pancreas and in circulation. Glutathione and NO were positively correlated in pancreas and lungs of controls but negatively correlated in circulation of experimental group. In the experimental group, plasma thiobarbituric acid reactive substances were negatively correlated with pancreas thiobarbituric acid reactive substances but positively correlated with pancreas NO.

CONCLUSION: NO increases in both pancreas and lungs in AP and NO contributes to the pathogenesis of AP under oxidative stress.

Melatonin ameliorates renal ischemia/reperfusion injury

BACKGROUND

We studied whether melatonin is able to reduce organ damage during renal ischemia/reperfusion via its effects on the oxidative response in early and late reperfusion.

MATERIALS AND METHODS

Renal ischemia/reperfusion injury (I/R) was induced in two groups of rats by 75 min occlusion of the left renal artery and vein and right nephrectomy, followed by reperfusion. The formation of reactive oxygen species was evaluated in the early reperfusion phase (60 min) by lipid peroxidation products and glutathione assay. In the late reperfusion phase (24 h) tissue neutrophil infiltration, inducible nitric oxide synthase (iNOS) gene expression, and histopathology were evaluated. Groups received either systemic melatonin (MEL) or normal saline (NS). There were two nonischemic sham control groups, one with and another without melatonin (S+MEL and S).

RESULTS

Creatinine was higher in the NS group at all times. A reduction in glutathione and increases in lipid peroxidation products and myeloperoxidase activity induced by I/R indicated renal injury involving reactive oxygen formation. Melatonin reversed this oxidant response and reduced the rise in creatinine and iNOS expression. Seven-day group survivals were 5/10 for NS, 8/10 for MEL, and 10/10 for both Sham groups.

CONCLUSIONS

Exogenous melatonin is able to preserve renal functional status following I/R-induced injury by increasing glutathione and reducing lipid peroxidation in the early reperfusion phase, without any apparent effect on neutrophil infiltration in the late reperfusion phase.

Hypertonic saline enhances host response to bacterial challenge by augmenting receptor-independent neutrophil intracellular superoxide formation

OBJECTIVE

This study sought to determine whether hypertonic saline (HTS) infusion modulates the host response to bacterial challenge.

METHODS

Sepsis was induced in 30 Balb-C mice by intraperitoneal injection of Escherichia coli (5 x 107 organisms per animal). In 10 mice, resuscitation was performed at 0 and 24 hours with a 4 mL/kg bolus of HTS (7.5% NaCl), 10 animals received 4 mL/kg of normal saline (0.9% NaCl), and the remaining animals received 30 mL/kg of normal saline. Samples of blood, spleen, and lung were cultured at 8 and 36 hours. Polymorphonucleocytes were incubated in isotonic or hypertonic medium before culture with E. coli. Phagocytosis was assessed by flow cytometry, whereas intracellular bacterial killing was measured after inhibition of phagocytosis with cytochalasin B. Intracellular formation of free radicals was assessed by the molecular probe CM-H(2)DCFDA. Mitogen-activated protein (MAP) kinase p38 and ERK-1 phosphorylation, and nuclear factor kappa B (NFkappaB) activation were determined. Data are represented as means (SEM), and an analysis of variance test was performed to gauge statistical significance.

RESULTS

Significantly reduced bacterial culture was observed in the animals resuscitated with HTS when compared with their NS counterparts, in blood (51.8 +/- 4.3 vs. 82.0 +/- 3.3 and 78.4 +/- 4.8, P = 0.005), lung (40.0 +/- 4.1 vs. 93.2 +/- 2.1 and 80.9 +/- 4.7, P = 0.002), and spleen (56.4 +/- 3.8 vs. 85.4 +/- 4.2 and 90.1 +/- 5.9, P = 0.05). Intracellular killing of bacteria increased markedly (P = 0.026) and superoxide generation was enhanced upon exposure to HTS (775.78 +/- 23.6 vs. 696.57 +/- 42.2, P = 0.017) despite inhibition of MAP kinase and NFkappaB activation.

CONCLUSIONS

HTS significantly enhances intracellular killing of bacteria while attenuating receptor-mediated activation of proinflammatory cascades.

Inhibition of cyclooxygenase-2 ameliorates the severity of pancreatitis and associated lung injury

Cyclooxygenase-2 (COX-2), a widely distributed enzyme, plays an important role in inflammation. We have studied the role of COX-2 in acute pancreatitis and pancreatitis-associated lung injury using both the pharmacological inhibition of COX-2 and genetic deletion of COX-2. Pancreatitis was induced in mice by 12 hourly injections of cerulein. The severity of pancreatitis was assessed by measuring serum amylase, pancreatic trypsin activity, intrapancreatic sequestration of neutrophils, and acinar cell necrosis. The severity of lung injury was evaluated by measuring lactate dehydrogenase levels in the bronchoalveolar lavage fluid and by quantitating neutrophil sequestration in the lung. In both the pharmacologically inhibited and genetically altered mice, the severity of pancreatitis and pancreatitis-associated lung injury was reduced compared with the noninhibited strains of COX-2-sufficient mice. This reduction in injury indicates that COX-2 plays an important proinflammatory role in pancreatitis and its associated lung injury. Our findings support the concept that COX-2 inhibitors may play a beneficial role in the prevention of acute pancreatitis or in the reduction of its severity.

The role of nitric oxide in edema formation in L-arginine-induced acute pancreatitis

INTRODUCTION

Nitric oxide (NO) has been implicated in the regulation of the pancreatic circulation, the promotion of the capillary integrity, and the inhibition of leukocyte adhesion.

AIMS

To investigate the rates of changes in the pancreatic constitutive NO synthase (cNOS) and inducible NOS (iNOS) activities and the role of NO in the vascular permeability changes during the development of L-arginine (Arg)-induced acute pancreatitis.

METHODOLOGY

Acute pancreatitis was induced in male Wistar rats by injecting 250 mg/100 g body weight of Arg i.p. twice at an interval of 1 hour, as a 20% solution in 0.15 NaCl (group I). The control rats received the same quantity of glycine (group II). In group III, 30 mg/kg N -nitro-L-arginine methyl ester (L-NAME) was injected i.p. 19 hours after the first Arg injection. The rats were killed at 6, 12, 24, or 48 hours following Arg administration, and the plasma amylase concentration and the pancreatic weight/body weight (pw/bw) ratios were evaluated. NOS activity was determined via the conversion of L- C-Arg monohydrochloride to C-citrulline. The vascular permeability was examined by means of the extravasation of Evans blue dye (20 mg/kg bw) into the pancreatic tissue.

RESULTS

The serum amylase level was already increased at 6 hours in group I animals, peaked at 12 hours after the Arg injection (11.800 +/- 590 versus 6.618 +/- 252 U/L in group II), and returned to the control level at 48 hours. The pw/bw ratio peaked at 24 hours in group I (6.63 +/- 0.52 versus 4.02 +/- 0.22 mg/g in group II) and returned to the control level at 48 hours. The cNOS activity was depleted at 6 hours in group I (0.02 +/- 0.003 versus 0.23 +/- 0.02 pmol/min/mg protein in group II); it then gradually increased to a level significantly higher than that in group II and decreased thereafter (0.45 +/- 0.03 and 0.13 +/- 0.01 pmol/min/mg protein at 24 and 48 hours). The iNOS activity was significantly increased at 24 and 48 hours versus that in group II (0.15 +/- 0.05 and 0.07 +/- 0.01 versus 0.04 +/- 0.01 pmol/min/mg protein). The pancreatic concentration of Evans blue dye was significantly higher in group I than in group II (138.59 +/- 11.04 versus 43.57 +/- 2.67 (g/dry weight). Treatment with L-NAME significantly reduced the amylase activity, pw/bw, Evans blue concentration, and cNOS activity of the pancreas but did not exert any beneficial effect on the histologic score at 24 hours after the onset of pancreatitis, as compared with those values in group I (6.528 +/- 673 U/L, 4.56 +/- 0.65 mg/g, 86.84 +/- 3.9 (g/dry weight, 0.14 +/- 0.04 pmol/min/mg protein).

CONCLUSION

Endogenous NO is involved in the formation of pancreatic edema in Arg-induced acute pancreatitis by increasing the vascular permeability and protein extravasation. L-NAME treatment decreased the cNOS activity and edema formation but did not prevent the histologic damage in Arg-induced acute pancreatitis.

Lung injury in acute pancreatitis: mechanisms, prevention, and therapy

Lung injury is the most pertinent manifestation of extra-abdominal organ dysfunction in pancreatitis. The propensity of this retroperitoneal inflammatory condition to engender a diffuse and life-threatening lung injury is significant. Approximately one third of patients will develop acute lung injury and acute respiratory distress syndrome, which account for 60% of all deaths within the first week. The variability in the clinical course of pancreatitis renders it a vexing entity and makes demonstration of the efficacy of any specific intervention difficult. The distinct pathologic entity of pancreatitis-associated lung injury is reviewed with a focus on etiology and potential therapeutic maneuvers.

Effect of exogenous melatonin on hepatic energetic status during ischemia/reperfusion: possible role of tumor necrosis factor-alpha and nitric oxide

BACKGROUND

This study was designed to determine if the very potent antioxidant melatonin is able to reduce organ damage and improve energetic status in an in situ liver ischemia/reperfusion model.

MATERIALS AND METHODS

Total hepatic ischemia was induced in rats by occlusion of the hepatic artery, portal vein, and bile duct. A portojugular shunt was inserted. After 60 min of ischemia, reperfusion was established for a period of 120 min. Rats were assigned to one group receiving systemic melatonin administration or to another receiving only normal saline. Variables were observed at preischemia, after 60 min of ischemia, and at 30, 60, and 120 min of reperfusion.

RESULTS

Energy charge, measured as the arterial ketone body ratio, showed higher values in the melatonin group during the first 60 min of reperfusion. Rises in plasma nitrite, tumor necrosis factor (TNF)-alpha, aspartate aminotransferase, alanine aminotransferase, lipid peroxidation products, and inducible nitric oxide synthase (iNOS) expression were less severe with melatonin. Linear regression analysis demonstrated a significant correlation between nitrites and arterial ketone body ratio (R(2) = 0.2454). Bile production was higher with melatonin. Seven-day survival rates were 52% for control, 80% for melatonin, and 100% for sham groups.

CONCLUSIONS

Exogenous melatonin is capable of preserving the functional and energetic status during ischemia/reperfusion which is associated with reduced concentrations of TNF-alpha and inhibited expression of iNOS and NO production. This improvement may be due to an adequate preservation of the hepatic mitochondrial redox status.

Inhibition of p38 mitogen activate kinase attenuates the severity of pancreatitis-induced adult respiratory distress syndrome

OBJECTIVE

Adult respiratory distress syndrome (ARDS) is responsible for a significant portion of the morbidity and mortality during severe acute pancreatitis. Because inflammatory mediators such as tumor necrosis factor (TNF)-alpha and nitric oxide (NO) produced within the lungs have been implicated in sepsis-induced ARDS, we aimed to determine the role of these mediators in pancreatitis-induced ARDS using a model whereby ascites from animals with pancreatitis is transferred to otherwise healthy animals resulting in pulmonary injury.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Research laboratory at a university medical school.

SUBJECTS

Pathogen-free Sprague-Dawley rats weighing 225-250 g.

INTERVENTIONS

Sterile, endotoxin- and cytokine-free pancreatic ascites tested for interleukin (IL)-1beta , TNF-alpha, interferon-gamma, and IL-6 was obtained from rats 18 hrs after the induction of severe, acute pancreatitis. Ascites was subsequently administered intravenously (20 mL/kg) to healthy rats. Sham animals were administered intravenous saline. Healthy animals administered intravenous ascites were randomized to receive a single intraperitoneal injection of the p38 mitogen activated kinase inhibitor CNI-1493 (1 mg/kg) or vehicle.

MEASUREMENTS

Pulmonary injury was assessed at 24 hrs by histology and leukocyte and protein concentrations via bronchoalveolar lavage. Pulmonary TNF-alpha protein was detected by immunohistochemistry. Serum nitrite, as a measure of NO production, was measured utilizing the Griess reaction.

MAIN RESULTS

After the intravenous administration of pancreatic ascites, the number of leukocytes and the protein concentration within the bronchoalveolar fluid were increased and pulmonary histology was worsened consistent with acute lung injury (all p < .001 vs. sham). Each of these variables of pulmonary injury was lessened in animals receiving CNI-1493 and intravenous ascites (p < .05 vs. vehicle). Pulmonary TNF-alpha protein and serum nitrites were decreased with the administration of CNI-1493 (p < .005 vs. vehicle).

CONCLUSIONS

A component of pancreatic ascites other than endotoxin, bacteria, or cytokines (IL-1beta, TNF, interferon-gamma, or IL-6) is capable of inducing ARDS in healthy animals. Inhibition of p38 mitogen activated kinase decreases the pulmonary injury through attenuated production of TNF-alpha and NO suggesting a primary role for these mediators in pancreatitis-induced ARDS.

Effects of inhaled nitric oxide in a rat model of Pseudomonas aeruginosa pneumonia

OBJECTIVE

Antimicrobial effects of nitric oxide (NO) have been demonstrated in vitro against a variety of infectious pathogens, yet in vivo evidence of a potential therapeutic role for exogenous NO as an antimicrobial agent is limited. Thus, we assessed the effects of inhaled NO on pulmonary infection, leukocyte infiltration, and NO synthase (NOS) activity in a rat model of Pseudomonas aeruginosa pneumonia.

DESIGN

Controlled animal study.

SETTING

Research laboratory of an academic institution.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

After intratracheal instillation of either P. aeruginosa or saline (sham), rats were randomly exposed to either 40 ppm of inhaled NO or room air (RA) for 24 hrs before they were killed.

MEASUREMENTS AND MAIN RESULTS

Inhaled NO in pneumonia rats markedly reduced pulmonary bacterial load (0.02+/-0.01% vs. 0.99+/-0.59% of bacterial input in pneumonia with room air, p < .05) and pulmonary myeloperoxidase activity, a marker of leukocyte infiltration (21.7+/-3.8 vs. 55.0+/-8.1 units in pneumonia with room air, p < .05), but had no effect on systemic hemodynamics or gas exchange. Pneumonia was associated with enhanced pulmonary NOS activity (8.8+/-2.4 vs. 0.2+/-0.1 pmol citrulline/min/mg protein in sham, p < .01) and increased plasma levels of nitrites/nitrates (NOx-; 45+/-7 vs. 16+/-3 micromol/L in sham, p < .01). Inhaled NO therapy attenuated the pneumonia-induced increase in pulmonary calcium-independent NOS activity (p < .05) and markedly increased plasma NOx- levels. Exposure of P. aeruginosa in culture to 40 ppm of ambient NO confirmed a delayed antibacterial effect of NO in vitro.

CONCLUSIONS

Inhaled NO has an important antibacterial effect both in vitro and in vivo against P. aeruginosa and is associated with reduced pulmonary leukocyte infiltration in vivo. These results in a rat model of P. aeruginosa pneumonia suggest that future studies should address the possible clinical effects of inhaled NO therapy in pneumonia.

Elastase mimics pancreatitis-induced hepatic injury via inflammatory mediators

BACKGROUND

Recent evidence suggests that pancreatitis-associated hepatic injury is regulated by inflammatory mediator production. Our laboratory demonstrated in vitro that pancreatic elastase is a pancreatic enzyme that can induce inflammatory cell cytokine production. Therefore we now explore the in vivo effects of elastase on the liver.

MATERIALS AND METHODS

Elastase (1.5 U) +/- CNI-1493, which attenuates mediator production through p38 MAP kinase inhibition, was administered intraperitoneally to mice while control animals received saline. Acute pancreatitis (AP) was induced with a choline-deficient, ethionine-supplemented (CDE) diet. Serum hepatic enzymes and hepatic neutrophil infiltration by myeloperoxidase (MPO) activity were measured as indicators of hepatic insult. Serum tumor necrosis factor (TNF) protein (ELISA), hepatic TNF mRNA (reverse transcription polymerase chain reaction), and hepatic activation of the transcription factor nuclear factor kappa B (electrophoretic mobility shift assay) were also determined.

RESULTS

A significant increase in hepatic enzymes and MPO activity was induced by AP and mirrored by intraperitoneal elastase. Both types of liver injury resulted in near identical elevations in serum TNF protein and hepatic TNF mRNA. Elastase-treated animals with mediator production inhibited (CNI-1493) had attenuated hepatic enzymes, MPO activity, TNF protein, and TNF mRNA. Activation of nuclear factor kappa B occurred 30 min after elastase administration.

CONCLUSION

Exposure of the liver to pancreatic elastase results in hepatic inflammation and injury which appears identical to that seen during severe AP. Prevention of inflammatory mediator production by intrahepatic leukocytes attenuates injury and supports recent adult respiratory distress syndrome and in vitro data suggesting that elastase is the principal factor that propagates pancreatic inflammation into a systemic illness through direct activation of systemic inflammatory cells.

Lysosomal activity of pulmonary alveolar macrophages in acute experimental pancreatitis in rats with reference to positive PAF-antagonist (BN 52021) effect

The activation of pulmonary alveolar macrophages (PAM's), might play an important role in severe complications of acute pancreatitis. The aim of our study was to assess the labilization of macrophage lysosomal membranes and release of lysosomal cathepsin B (CB) and N-acetyl-beta-D-hexosaminidase (NAH) into bronchoalveolar lavage fluid (BALF) during taurocholate acute pancreatitis (AP) in rats treated with PAF-antagonist--BN 52021. Total activity of CB increased by 374% after 6 h and by 237% after 12 h of AP in lysosomal enriched fraction of PAM's. Fractional free activity of CB increased to 40% after 6 h and to 38% after 12 h of AP. Free activity of CB was increased 5 fold in the supernatant of macrophage homogenate, and 10 fold in the supernatant of BALF after 6 h of AP. The values of NAH activity roughly paralleled that of CB. Treatment with BN 52021 (5 mg x kg(-1) every 6 h i.v.) partially normalized the measured parameters. Our results indicate that the PAF-antagonist BN 52021 reduced the increase of total and free activity of lysosomal hydrolases of PAM's and partly prevented the labilization of their lysosomal membranes. Therefore, an important mechanism of BN 52021 beneficial effect in pulmonary complications of acute pancreatitis could be dependent on the stabilization of PAM's lysosomes.

Bradykinin B2-receptor antagonism attenuates fatal cardiocirculatory breakdown induced by severe experimental pancreatitis

OBJECTIVES

To investigate the impact of the long-acting bradykinin B2 receptor antagonist HOE 140 (Icatibant) on survival time in a model of severe porcine pancreatitis.

DESIGN

Randomized, controlled intervention trial.

SUBJECTS

Thirty domestic pigs of either gender anesthetized by intravenous application of piritramide, midazolam, and pancuronium and mechanically ventilated.

INTERVENTIONS

Pancreatitis was induced by an injection of sodium taurocholate (5%, 1 mL/kg body weight [BW]) and enterokinase (10 U/kg BW). Control animals (group 1, n = 10) underwent the spontaneous course of the disease. In two treatment groups, Icatibant was administered either in a low (100 nmol/kg BW; group 2, n = 10) or in a high dosage (5000 nmol/kg BW; group 3, n = 10).

MEASUREMENTS AND MAIN RESULTS

Mean survival time was significantly prolonged by Icatibant (controls, 6.6 hrs; group 2, 9.8 hrs; p = .022; group 3, 10.9 hrs; p = .007). Six hours postinduction, the decline of total peripheral resistance (52% of baseline) and cardiac index (92% of baseline) in controls was significantly improved by Icatibant, both in the low (16% and 44%; p < .05) and high (6% and 45%; p < .05) dosage. The concentrations of free, nonreceptor-bound kinin in plasma 6 hrs postinduction were significantly lower in controls than in groups 2 and 3 animals (111+/-50 vs. 208+/-40 and 237+/-52 fmol/mL, respectively). Six hours postinduction, the pretreatment with Icatibant was associated with significantly higher plasma concentrations of phospholipase A2 (controls, +1194%; group 2, +2000%; group 3, +2285% of baseline values) and interleukin-1 receptor antagonist (controls, 1900+/-800; group 2, 3100+/-800; group 3, 3600+/-800 pg/mL). In contrast, the increase of urinary trypsinogen activation peptides indicating local pancreatic damage (589+/-114 nmol/L in controls) was substantially attenuated by pretreatment with Icatibant (group 2, 467+/-102, NS; 352+/-91 nmol/L in group 3; p = .022 vs. controls). Systemic inflammatory reactions, however, as quantified by C-reactive protein and the extracellularly discharged neutrophil cytosolic inhibitor leukocyte neutral proteinase inhibitor were not influenced by the bradykinin B2-receptor antagonist.

CONCLUSIONS

Pretreatment with the bradykinin B2 receptor antagonist Icatibant resulted in prolonged survival time and in delayed impairment of major macrocirculatory and pulmonary variables. Icatibant resulted in elevated concentrations of free, circulating kinin. This was associated with increased concentrations of phospholipase A2 and interleukin-1 receptor antagonist, suggesting that circulating kinins strengthen the activation of some mediator cascades, the association of which with the kinin metabolism requires further experimental clarification. Other variables indicating a systemic inflammatory response (C-reactive protein, leukocyte neutral proteinase inhibitor) remained unaffected by Icatibant. Bradykinin antagonism distinctly ameliorated the local pancreatic damage, indicated by increased urinary concentrations of trypsinogen activation peptides. It is concluded that the kinin metabolism plays an important role in the pathophysiology of systemic complications after severe experimental pancreatitis.

Nitric oxide decreases endothelial activation by rat experimental severe pancreatitis-associated ascitic fluids

To clarify the roles of nitric oxide (NO) in acute pancreatitis (AP), we examined the effects of NO on the endothelial activation induced by ascitic fluids from rats with experimental severe AP. Necrotizing hemorrhagic pancreatitis was induced in male Wistar rats with sodium taurocholate. Six hours later, peritoneal exudates were collected, centrifuged, and human umbilical vein endothelial cells were treated with the supernatants. Then (a) the mRNA level of endothelial-type NO synthase (ecNOS) was examined by reverse transcription-polymerase chain reaction; (b) effects of an NO donor, sodium nitroprusside (SNP) and an inhibitor of NOS, N(omega)-nitro-L-arginine (L-NNA) on the ascitic fluids-induced expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and interleukin-8 were assessed by enzyme-linked immunoassay; (c) nuclear translocation of nuclear factor-kappa B (NF-kappaB) was examined by electrophoretic mobility shift assay; and (d) effects of SNP and L-NNA on the adhesion of U937 cells to endothelial monolayer were assessed. The ecNOS mRNA level was decreased by the ascitic fluids; ascitic fluids-induced expression of adhesion molecules and interleukin-8 as well as the nuclear translocation of NF-kappaB were attenuated by SNP, whereas L-NNA augmented them; and the effects on the endothelial activation were paralleled by the altered adhesion of U937 cells to endothelium. The ability of NO to limit endothelial activation and inhibit leukocyte adhesion might contribute to its antiinflammatory properties in AP.

Phospholipase A2 mediates nitric oxide production by alveolar macrophages and acute lung injury in pancreatitis

OBJECTIVE

Reportedly, nitric oxide (NO) derived from alveolar macrophages (AMs) and increased serum phospholipase A2 (PLA2) activity are associated with the pathogenesis of lung injury in acute pancreatitis. The authors examined the possibility that PLA2 causes, in part, the induction of NO production by AMs in pancreatitis.

METHODS

Pancreatitis was induced in rats by selective pancreatic duct ligation (SPL). AMs were stimulated with PLA2 or SPL rat serum, with or without administration of the PLA2 inhibitor quinacrine. Then NO production from the AMs was measured by the Griess method, inducible NO synthase mRNA expression of AMs was analyzed by the reverse transcription-polymerase chain reaction, and cytotoxic effects of AMs on human umbilical vein endothelial cells was examined by a 51Cr release assay. In vivo, the effect of quinacrine on lung injury was determined by measuring the arterial blood oxygen pressure (PaO2), lung weight, and lung permeability using Evans blue dye concentration of SPL rat.

RESULTS

In vitro, the serum with high PLA2 activity induced NO production by rat AMs. PLA2 (50 ng/ml) induced significant amounts of NO production, inducible NO synthase mRNA expression, and cytotoxicity toward the human umbilical vein endothelial cells in normal rat AMs, and these activities were significantly inhibited by quinacrine. In vivo, rats with pancreatitis that were given quinacrine showed decreased concentrations of NO2- and NO3- in the bronchoalveolar lavage fluid, and the PaO2, lung edema, and lung permeability were improved significantly.

CONCLUSION

PLA2 induces AMs to release NO, which contributes to lung injury in acute pancreatitis. This lung injury was prevented by the administration of the PLA2 inhibitor quinacrine.

Activation of alveolar macrophages in lung injury associated with experimental acute pancreatitis is mediated by the liver

OBJECTIVE

To evaluate (1) whether alveolar macrophages are activated as a consequence of acute pancreatitis (AP), (2) the implication of inflammatory factors released by these macrophages in the process of neutrophil migration into the lungs observed in lung injury induced by AP, and (3) the role of the liver in the activation of alveolar macrophages.

SUMMARY BACKGROUND DATA

Acute lung injury is the extrapancreatic complication most frequently associated with death and complications in severe AP. Neutrophil infiltration into the lungs seems to be related to the release of systemic and local mediators. The liver and alveolar macrophages are sources of mediators that have been suggested to participate in the lung damage associated with AP.

METHODS

Pancreatitis was induced in rats by intraductal administration of 5% sodium taurocholate. The inflammatory process in the lung and the activation of alveolar macrophages were investigated in animals with and without portocaval shunting 3 hours after AP induction. Alveolar macrophages were obtained by bronchoalveolar lavage. The generation of nitric oxide, leukotriene B4, tumor necrosis factor-alpha, and MIP-2 by alveolar macrophages and the chemotactic activity of supernatants of cultured macrophages were evaluated.

RESULTS

Pancreatitis was associated with increased infiltration of neutrophils into the lungs 3 hours after induction. This effect was prevented by the portocaval shunt. Alveolar macrophages obtained after induction of pancreatitis generated increased levels of nitric oxide, tumor necrosis factor-alpha, and MIP-2, but not leukotriene B4. In addition, supernatants of these macrophages exhibited a chemotactic activity for neutrophils when instilled into the lungs of unmanipulated animals. All these effects were abolished when portocaval shunting was carried out before induction of pancreatitis.

CONCLUSION

Lung damage induced by experimental AP is associated with alveolar macrophage activation. The liver mediates the alveolar macrophage activation in this experimental model.

Nitric oxide participates in early events associated with NNMU-induced acute lung injury in rats

In this study, the biochemical mechanisms by which N-nitroso-N-methylurethane (NNMU) induces acute lung injury are examined. Polymorphonuclear neutrophil infiltration into the lungs first appears in the bronchoalveolar lavage (BAL) fluid 24 h after NNMU injection (10.58 +/- 3.00% of total cells; P < 0.05 vs. control animals). However, NNMU-induced elevation of the alveolar-arterial O2 difference requires 72 h to develop. Daily intraperitoneal injections of the inducible nitric oxide (. NO) synthase (iNOS)-selective inhibitor aminoguanidine (AG) initiated 24 h after NNMU administration improve the survival of NNMU-treated animals. However, AG administration initiated 48 or 72 h after NNMU injection does not significantly improve the survival of NNMU-treated animals. These results suggest that. NO participates in events that occur early in NNMU-induced acute lung injury. BAL cells isolated from rats 24 and 48 h after NNMU injection produce elevated. NO and express iNOS during a 24-h ex vivo culture. AG attenuates. NO production but does not affect iNOS expression, whereas actinomycin D prevents iNOS expression and attenuates. NO production by BAL cells during this ex vivo culture. These results suggest that NNMU-derived BAL cells can stimulate iNOS expression and. NO production during culture. In 48-h NNMU-exposed rats, iNOS expression is elevated in homogenates of whole lavaged lungs but not in BAL cells derived from the same lung. These findings suggest that the pathogenic mechanism by which NNMU induces acute lung injury involves BAL cell stimulation of iNOS expression and. NO production in lung tissue.

Macrophage pacification reduces rodent pancreatitis-induced hepatocellular injury through down-regulation of hepatic tumor necrosis factor alpha and interleukin-1beta

Overproduction of tumor necrosis factor (TNF-), interleukin-1beta (IL-1beta), and nitric oxide (NO) is believed to be detrimental during the progression of acute pancreatitis, yet little is known about the hepatic production of these mediators and their role in mediating pancreatitis-induced hepatic dysfunction. Rats were randomized to receive a single intraperitoneal injection of the macrophage-pacifying compound, CNI-1493 (1.0 mg/kg), or vehicle 1 hour before the induction of retrograde bile salt pancreatitis. Sham-operated animals served as controls. Animals were killed 18 hours later, with serum and livers harvested to determine the degree of hepatocellular injury and the induction of TNF-, IL-1beta, and inducible nitric oxide synthase (iNOS). In addition, serum TNF- and nitrites (end-product of NO breakdown) were determined in each group to assess the mechanism of action of CNI-1493. TNF-, IL-1beta, and iNOS gene expression (by reverse-transcription polymerase chain reaction) as well as aspartate transaminase (AST), alanine transaminase (ALT), and lactic dehydrogenase (LDH) (but not alkaline phosphatase [ALP]) increased following the development of pancreatitis (all P < .05). Macrophage pacification significantly prevented the induction of TNF- and IL-1beta mRNA (but not iNOS), resulting in lessened serum AST, ALT, and LDH (all P < .05). Serum TNF- protein and nitrites correlated with gene induction in that both were increased following the onset of pancreatitis, and TNF- protein production was significantly attenuated in animals receiving CNI-1493. Hepatocellular, but not bile duct, injury occurs during experimental pancreatitis that is associated with hepatic TNF-, IL-1beta, and iNOS mRNA gene induction, as well as TNF- protein and nitrite production. Preventing the production of TNF- and IL-1beta by macrophage pacification attenuates the hepatocellular damage, suggesting that these mediators play a role in pancreatitis-induced hepatic injury.