Free radical inhibition and serial chemiluminescence in evolving experimental pancreatitis

Efficacy of enteral glutamine supplementation in patients with severe and predicted severe acute pancreatitis- A randomized controlled trial

BACKGROUND

In severe acute pancreatitis (AP), intravenous glutamine has been shown to reduce the rate of complications, hospital stay, and mortality. In the present randomized trial, we aimed to evaluate the effect of enteral glutamine supplementation on clinical outcomes, gut permeability, systemic inflammation, oxidative stress, and plasma glutamine levels in patients with severe and predicted severe AP.

METHODS

Patients with AP admitted within 72 h of onset of symptoms were included. The primary outcome measure was development of infected pancreatic and peri-pancreatic necrosis and in-hospital mortality. High-sensitivity C-reactive protein (HS-CRP) and interleukin-6 (IL-6) were evaluated as markers of inflammation; plasma thiobarbituric acid reactive substances (TBARS) and activities of serum superoxide dismutase and glutathione peroxidase were determined to evaluate oxidative stress; serum polyethylene glycol (PEG) was tested for intestinal permeability; subjective global assessment (SGA) was used for nutritional assessment, and an improvement in organ function was measured by the Modified Marshall score. Intention-to-treat analysis was used. A p-value of < 0.05 was considered statistically significant.

RESULTS

After power calculation, we enrolled 18 patients in the glutamine and 22 in the control arm. There was no significant improvement in the development of infected necrosis and in-hospital mortality between the groups. Improvement in Modified Marshall score was observed in a higher proportion of patients receiving glutamine (15 [83.3%] vs. 12 [54.5%]; p = 0.05). Plasma glutamine levels improved more in glutamine-treated group (432.72 ± 307.83 vs. 618.06 ± 543.29 μM/L; p = 0.004), while it was lower in controls (576.90 ± 477.97 vs. 528.20 ± 410.45 μM/L; p = 0.003). PEG level was lower after glutamine supplementation (39.91 ± 11.97 vs. 32.30 ± 7.39 ng/mL; p = 0.02). Statistically significant reduction in IL-6 concentration was observed in the glutamine group at the end of treatment (87.44 ± 7.1 vs. 63.42 ± 33.7 μM/L; p = 0.02).

CONCLUSIONS

Despite absence of improvement in infected necrosis and in-hospital mortality, enteral glutamine supplementation showed improvement in gut permeability, oxidative stress, and a trend towards improvement in organ function as depicted by improvement in the Modified Marshall score.

TRIAL REGISTRATION

NCT01503320.

Docosahexaenoic Acid Inhibits Cerulein-Induced Acute Pancreatitis in Rats

Oxidative stress is an important regulator in the pathogenesis of acute pancreatitis (AP). Reactive oxygen species induce activation of inflammatory cascades, inflammatory cell recruitment, and tissue damage. NF-κB regulates inflammatory cytokine gene expression, which induces an acute, edematous form of pancreatitis. Protein kinase C δ (PKCδ) activates NF-κB as shown in a mouse model of cerulein-induced AP. Docosahexaenoic acid (DHA), an ω-3 fatty acid, exerts anti-inflammatory and antioxidant effects in various cells and tissues. This study investigated whether DHA inhibits cerulein-induced AP in rats by assessing pancreatic edema, myeloperoxidase activity, levels of lipid peroxide and IL-6, activation of NF-κB and PKCδ, and by histologic observation. AP was induced by intraperitoneal injection (i.p.) of cerulein (50 μg/kg) every hour for 7 h. DHA (13 mg/kg) was administered i.p. for three days before AP induction. Pretreatment with DHA reduced cerulein-induced activation of NF-κB, PKCδ, and IL-6 in pancreatic tissues of rats. DHA suppressed pancreatic edema and decreased the abundance of lipid peroxide, myeloperoxidase activity, and inflammatory cell infiltration into the pancreatic tissues of cerulein-stimulated rats. Therefore, DHA may help prevent the development of pancreatitis by suppressing the activation of NF-κB and PKCδ, expression of IL-6, and oxidative damage to the pancreas.

Docosahexaenoic acid inhibits IL-6 expression via PPARγ-mediated expression of catalase in cerulein-stimulated pancreatic acinar cells

Cerulein pancreatitis mirrors human acute pancreatitis. In pancreatic acinar cells exposed to cerulein, reactive oxygen species (ROS) mediate inflammatory signaling by Janus kinase (JAK) 2/signal transducer and activator of transcription (STAT) 3, and cytokine induction. Docosahexaenoic acid (DHA) acts as an agonist of peroxisome proliferator activated receptor γ (PPARγ), which mediates the expression of some antioxidant enzymes. We hypothesized that DHA may induce PPARγ-target catalase expression and reduce ROS levels, leading to the inhibition of JAK2/STAT3 activation and IL-6 expression in cerulein-stimulated acinar cells. Pancreatic acinar AR42J cells were treated with DHA in the presence or absence of the PPARγ antagonist GW9662, or treated with the PPARγ agonist troglitazone, and then stimulated with cerulein. Expression of IL-6 and catalase, ROS levels, JAK2/STAT3 activation, and nuclear translocation of PPARγ were assessed. DHA suppressed the increase in ROS, JAK2/STAT3 activation, and IL-6 expression induced nuclear translocation of PPARγ and catalase expression in cerulein-stimulated AR42J cells. Troglitazone inhibited the cerulein-induced increase in ROS and IL-6 expression, but induced catalase expression similar to DHA in AR42J cells. GW9662 abolished the inhibitory effect of DHA on cerulein-induced increase in ROS and IL-6 expression in AR42J cells. DHA-induced expression of catalase was suppressed by GW9662 in cerulein-stimulated AR42J cells. Thus, DHA induces PPARγ activation and catalase expression, which inhibits ROS-mediated activation of JAK2/STAT3 and IL-6 expression in cerulein-stimulated pancreatic acinar cells.

Tempol, a Membrane-Permeable Radical Scavenger, Exhibits Anti-Inflammatory and Cardioprotective Effects in the Cerulein-Induced Pancreatitis Rat Model

To date, it remains unclear whether mild form of acute pancreatitis (AP) may cause myocardial damage which may be asymptomatic for a long time. Pathogenesis of AP-related cardiac injury may be attributed in part to ROS/RNS overproduction. The aim of the present study was to evaluate the oxidative stress changes in both the pancreas and the heart and to estimate the protective effects of 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (tempol) at the early phase of AP. Cerulein-induced AP led to the development of acute edematous pancreatitis with a significant decrease in the level of sulfhydryl (–SH) groups (oxidation marker) both in heart and in pancreatic tissues as well as a substantial increase in plasma creatine kinase isoenzyme (CK-MB) activity (marker of the heart muscle lesion) which confirmed the role of oxidative stress in the pathogenesis of cardiac damage. The tempol treatment significantly reduced the intensity of inflammation and oxidative damage and decreased the morphological evidence of pancreas injury at early AP stages. Moreover, it markedly attenuated AP-induced cardiac damage revealed by normalization of the –SH group levels and CK-MB activity. On the basis of these studies, it is possible to conclude that tempol has a profound protective effect against cardiac and pancreatic damage induced by AP.

Protective effects of polyenoylphosphatidylcholine in rats with severe acute pancreatitis

OBJECTIVE

The aim of this study was to investigate the protective effect of polyenoylphosphatidylcholine (PPC) in rats with severe acute pancreatitis (SAP) and its mechanism.

METHODS

Seventy-two clean, conventional Sprague-Dawley rats were randomly divided into 4 groups (SAP; sham operation [SO], SAP + PPC, and SO + PPC; n = 18 per group). The SAP model was induced by injecting 4% sodium taurocholate (1 mL/kg) into the biliopancreatic duct. Animals in the SO groups underwent laparotomy and biliopancreatic duct puncture without fluid injection. Polyenoylphosphatidylcholine (50 mg/kg) was injected through the penis dorsal vein. Pancreatic acinar cell membrane fluidity and pancreatic tissue calcium pump activity were measured through fluorescence polarization and quantization of phosphonium ions, whereas pancreatic tissue superoxide dismutase and malondialdehyde were detected through xanthine oxidase method and thiobarbituric acid colorimetric analysis method, respectively.

RESULTS

The SAP + PPC group had significantly improved pathologic pancreas; increased in pancreatic acinar cell membrane fluidity, pancreatic tissue Ca-Mg-ATPase activity, and superoxide dismutase; as well as decreased in malondialdehyde, ascites volume, and serum amylase compared with the SAP group.

CONCLUSIONS

Polyenoylphosphatidylcholine could reduce the damage to the pancreas through increasing pancreatic acinar cell membrane fluidity and pancreatic tissue calcium pump activity. Polyenoylphosphatidylcholine also scavenges oxygen free radicals and reduces lipid peroxide levels.

Role of janus kinase/signal transducers and activators of transcription in the pathogenesis of pancreatitis and pancreatic cancer

In the pathogenesis of pancreatitis, oxidative stress is involved in the activation of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway and cytokine expression. High serum levels of cholecystokinin (CCK) have been reported in patients with acute pancreatitis, and treatment with cerulein, a CCK analogue, induces acute pancreatitis in a rodent model. Recent studies have shown that cerulein-activated nicotinamide adenine dinucleotide phosphate oxidase elicits reactive oxygen species, which trigger the phosphorylation of the JAK1, STAT1, and STAT3 proteins and induce the production of inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β, and IL-6, in pancreatic acinar cells. The JAK/STAT pathway also stimulates cell proliferation and malignant transformation and inhibits apoptosis in the pancreas. This review discusses the possible role of the JAK/STAT pathway in the pathogenesis of pancreatitis and pancreatic cancer in response to oxidative stress.

Calcium and reactive oxygen species in acute pancreatitis: friend or foe?

SIGNIFICANCE

Acute pancreatitis (AP) is a debilitating and, at times, lethal inflammatory disease, the causes and progression of which are incompletely understood. Disruption of Ca(2+) homeostasis in response to precipitants of AP leads to loss of mitochondrial integrity and cellular necrosis.

RECENT ADVANCES

While oxidative stress has been implicated as a major player in the pathogenesis of this disease, its precise roles remain to be defined. Recent developments are challenging the perception of reactive oxygen species (ROS) as nonspecific cytotoxic agents, suggesting that ROS promote apoptosis that may play a vital protective role in cellular stress since necrosis is avoided.

CRITICAL ISSUES

Fresh clinical findings have indicated that antioxidant treatment does not ameliorate AP and may actually worsen the outcome. This review explores the complex links between cellular Ca(2+) signaling and the intracellular redox environment, with particular relevance to AP.

FUTURE DIRECTIONS

Recent publications have underlined the importance of both Ca(2+) and ROS within the pathogenesis of AP, particularly in the determination of cell fate. Future research should elucidate the subtle interplay between Ca(2+) and redox mechanisms that operate to modulate mitochondrial function, with a view to devising strategies for the preservation of organellar function.

The contradictory effects of nitric oxide in caerulein-induced acute pancreatitis in rats

This study was planned to observe the effects of nitric oxide synthesis on the antioxidative defense enzymes and pancreatic tissue histology in caerulein-induced acute pancreatitis. Acute pancreatitis was induced by intraperitoneal injections of 50 microg/kg caerulein, L-arginine used for NO induction and N(omega)-nitro-L-arginine methyl ester (L-NAME) used for NO inhibition. In the caerulein group acinar cell degeneration, interstitial inflammation, oedema and haemorrhage were detected. Pancreatic damage scores were decreased with both NO induction and inhibition (p<0.05). MDA, GSH-Px, CAT, GSH and SOD activities were significantly changed in the caerulein group and indicated increased oxidative stress. Both NO induction and inhibition decreased this oxidative stress. It is concluded that both nitric oxide induction and inhibition ameliorated caerulein-induced acute pancreatitis. The findings indicate that a certain amount of NO production has beneficial effects in experimental acute pancreatitis, but uncontrolled over-production of NO may be detrimental.

Diphenyleneiodonium suppresses apoptosis in cerulein-stimulated pancreatic acinar cells

NADPH oxidase has been considered a major source of reactive oxygen species in phagocytic and non-phagocytic cells. Apoptosis linked to oxidative stress has been implicated in pancreatitis. Recently, we demonstrated that NADPH oxidase subunits Nox1, p27phox, p47phox, and p67phox are constitutively expressed in pancreatic acinar cells, which are activated by cerulein, a cholecystokinin analogue. Cerulein induces an acute and edematous form of pancreatitis. We investigated whether inhibition of NADPH oxidase by diphenyleneiodonium suppresses the production of reactive oxygen species and apoptosis by determining viable cell numbers, DNA fragmentation, TUNEL staining, caspase-3 activity, and the expression of apoptosis-inducing factor in pancreatic acinar AR42J cells stimulated with cerulein. Inhibition on NADPH oxidase by diphenyleneiodonium was assessed by the alterations in NADPH oxidase activity and translocation of the cytosolic subunits p67phox and p47phox to the membrane. Intracellular Ca2+ level was monitored to investigate the relationship between NADPH oxidase and Ca2+ in cells stimulated with cerulein. As a result, cerulein induced the activation of NADPH, increased production of reactive oxygen species, and apoptotic indices determined by the expression of apoptosis-inducing factor, caspase-3 activation, TUNEL staining, DNA fragmentation, and cell viability. Treatment with DPI inhibited cerulein-induced activation of NADPH oxidase, the production of reactive oxygen species, and apoptosis, but not the increase of intracellular Ca2+ levels in pancreatic acinar cells. These results demonstrate that the cerulein-induced increase in intracellular Ca2+ level may be an upstream event of NADPH oxidase activation. Diphenyleneiodonium, an NADPH oxidase inhibitor, inhibits the expression of apoptosis-inducing factor and caspase-3 activation, and thus apoptosis in pancreatic acinar cells.

Role of NADPH oxidase and calcium in cerulein-induced apoptosis: involvement of apoptosis-inducing factor

Apoptosis linked to oxidative stress has been implicated in pancreatitis. NADPH oxidase has been considered as a major source of reactive oxygen species (ROS) during inflammation and apoptosis in pancreatic acinar cells. Recently we demonstrated that NADPH oxidase subunits Nox1, p27phox, p47phox, and p67phox are constitutively expressed in pancreatic acinar cells and may contribute to apoptosis in pancreatic acinar AR42J cells stimulated with cerulein. The present study aims to investigate the apoptotic mechanism of pancreatic acinar cells stimulated with cerulein by determining whether cerulein induces apoptosis-inducing factor (AIF) expression and whether cerulein-induced expression of AIF is inhibited by transfection with antisense oligonucleotide (AS ODN) of p47phox or p67phox or treatment with a Ca2+ chelator BAPTA-AM. As a result, cerulein induced the expression of apoptotic gene AIF. Transfection with AS ODN of p47phox or p67phox or treatment with BAPTA-AM inhibited cerulein-induced AIF expression in pancreatic acinar AR42J cells. These results demonstrate that NADPH oxidase and calcium have a role in cerulein-induced apoptosis in pancreatic acinar AR42J cells by inducing the expression of AIF. In conclusion, the increase in intracellular Ca2+ and NADPH oxidase activity may be the upstream event of apoptotic gene (AIF) expression, which contributes to cerulein-induced apoptosis in pancreatic acinar AR42 cells.

Hydrogen peroxide-induced activation of defense mechanisms against oxidative stress in rat pancreatic acinar AR42J cells

Oxidative stress has been implicated in the pathogenesis of acute pancreatitis. Generally, cells respond to oxidative stress with adaptive changes in gene expression aimed at preventing cellular damage and increasing their survival. However, the overall extent of these genetic changes remains poorly defined. This issue was, therefore, examined in the current study. Following exposure of rat pancreatic AR42J cells to 0.08 mM hydrogen peroxide (H(2)O(2)), a concentration failing to induce necrotic cell death, the expression of 96 stress-related genes was monitored by cDNA microarray analysis. H(2)O(2) provoked a time-dependent reorientation of 54 genes. In particular, at 6 and 24 h, 27 and 11 genes were induced, whereas 10 and 6 genes were suppressed, respectively, showing that the degree of change was stronger at the early time point, and that the number of up-regulated genes was obviously larger than the number of down-regulated genes. Reverse transcription-PCR for selected genes confirmed the gene expression pattern. Many of the differentially up-regulated genes can be related to the antioxidant enzymatic defense system, to cell cycle arrest, to repair and/or replacement of damaged DNA, to repair of damaged protein, and to activation of the NF-kappaB pathway. The results suggest that AR42J cells respond to sublethal oxidative stress with transient transcriptional activation of multiple defense mechanisms that may be an indication for a complex adaptation process. An understanding of the cellular stress responses may lead to new insights into the pathogenesis of oxidative stress-related diseases including acute pancreatitis.

Alleviation of cell damage in experimental ANP in rats by administration of chondroitin-sulfate reduces

In order to explore the effects of retrograde infusion of chondroitin-sulfate via the pancreatic duct on cytoprotection and attenuation of oxidative damage during acute necrotic pancreatitis (ANP), male Wistar rats were randomly divided into three groups: A, B (experimental groups) and C (sham operation, control group). The rats in group A was subjected to retrograde injection of 5% sodium taurocholate via the pancreatic duct, and those in group B received chondroitin-sulfate therapy after ANP induction. All rats in three groups were killed at 6 h. The levels of malondialdehyde (MAD), total superoxide dismutase (SOD), glutathione (GSH), adenosine triphosphate (ATP) and serum amylase (SAM) were measured. The morphologic changes in pancreatic tissues were observed. It was found that the level of SAM was increased in group A and group B, with corresponding pathological changes of ANP. The levels of ATP, GSH and SOD in group A were decreased markedly and MDN increased significantly as compared with those in group B (P<0.01). In group B, the histopathologic damage was attenuated to a certain extent in comparison to that in group A. It was concluded that endogenous antioxidants were significantly reduced and lipid peroxidation increased during ANP. Retrograde infusion of chondroitin-sulfate via pancreatic duct could alleviate the pancreatic cell damage as a sort of scavengers of oxygen free radicals.

Free radicals and the pancreatic acinar cells: role in physiology and pathology

Reactive oxygen and nitrogen species (ROS and RNS) play an important role in signal transduction and cell injury processes. Nitric oxide synthase (NOS)-the key enzyme producing nitric oxide (NO)-is found in neuronal structures, vascular endothelium and, possibly, in acinar and ductal epithelial cells in the pancreas. NO is known to regulate cell homeostasis, and its effects on the acinar cells are reviewed here. ROS are implicated in the early events within the acinar cells, leading to the development of acute pancreatitis. The available data on ROS/RNS involvement in the apoptotic and necrotic death of pancreatic acinar cells will be discussed.

N-acetylcysteine does not prevent post-endoscopic retrograde cholangiopancreatography hyperamylasemia and acute pancreatitis

AIM: Acute pancreatitis (AP) is the most common and often severe complication of endoscopic retrograde cholangiopancreatography (ERCP). The early step in the pathogenesis of acute pancreatitis is probably the capillary endothelial injury mediated by oxygen-derived free radicals. N-acetylcysteine - a free radical scavenger may be potentially effective in preventing post-ERCP acute pancreatitis and it is also known that N-acetylcysteine (ACC) can reduce the severity of disease in experimental model of AP.

METHODS: One hundred and six patients were randomly allocated to two groups. Fifty-five patients were given N-acetylcysteine (two 600 mg doses orally 24 and 12 h before ERCP and 600 mg was given iv, twice a day for two days after the ERCP). The control group consisted of 51 patients who were given iv. isotonic saline twice a day for two days after the ERCP. Serum and urine amylase activities were measured before ERCP and 8 and 24 h after the procedure. The primary outcome parameter was post-ERCP acute pancreatitis and the secondary outcome parameters were differences between groups in serum and urine amylase activity.

RESULTS: There were no significant differences in the rate of post-ERCP pancreatitis between two groups (10 patients overall, 4 in the ACC group and 6 in the control group). There were also no significant differences in baseline and post-ERCP serum and urine amylase activity between ACC group and control group.

CONCLUSION: N-acetylcysteine fails to demonstrate any significant preventive effect on post-ERCP pancreatitis, as well as on serum and urine amylase activity.

NADPH oxidase mediates interleukin-6 expression in cerulein-stimulated pancreatic acinar cells

NADPH oxidase produces a large amount of reactive oxygen species (ROS) mainly in phagocytic cells. ROS are involved in NF-kappaB activation, cytokine expression and thus, pathogenesis of pancreatitis. However, the source of ROS in pancreatic acinar cells has not been clarified. Cerulein rapidly induces acute and edematous form of pancreatitis. We investigated whether pancreatic acinar cells contain NADPH oxidase, and whether NADPH oxidase mediates interleukin-6 (IL-6) in pancreatic acinar AR42J cells stimulated with cerulein. Expression of NADPH oxidase subunits and NADPH oxidase activity were determined in the cells by immunofluorescence staining and lucigenin luminescence, respectively. Oxidant-sensitive nuclear transcription factor NF-kappaB activation was monitored by electrophoretic mobility shift assay. IL-6 expression was determined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbant assay. NADPH oxidase inhibitor diphenylene iodonium (DPI), antioxidant rebamipide, and antisense oligonucleotides (AS ODNs) for NADPH oxidase subunits p22phox and p47phox were used to determine the involvement of NADPH oxidase in NF-kappaB activation and IL-6 expression in AR42J cells. As a result, pancreatic acinar AR42J cells constitutively express NADPH oxidase subunits p67phox and p47phox in the cytosol and Nox1 and p22phox in the membrane. Cerulein-stimulated NADPH oxidase activity and induced NF-kappaB activation and IL-6 expression in AR42J cells. Treatment of DPI or rebamipide and transfection of AS ODNs for NADPH oxidase subunits suppressed cerulein-induced NF-kappaB activation and IL-6 expression compared to S ODNs. In conclusion, NADPH oxidase may mediate the expression of inflammatory cytokines by stimulating NF-kappaB activation in pancreatic acinar cells during the course of pancreatitis.

NADPH oxidase and apoptosis in cerulein-stimulated pancreatic acinar AR42J cells

Apoptosis linked to oxidative stress has been implicated in pancreatitis. We investigated whether NADPH oxidase mediates apoptosis in cerulein-stimulated pancreatic acinar AR42J cells. We report here that cerulein treatment resulted in the activation of NADPH oxidase, as determined by ROS production, translocation of cytosolic subunits p 47(phox) and p 67(phox) to the membrane, and interaction between NADPH oxidase subunits. Cerulein induced Ca(2+) oscillation, the expression of apoptotic genes p53 and bax, and apoptotic indices (DNA fragmentation, TUNEL staining, caspase 3 activity, decrease in cell viability) in AR42J cells. Treatment with a Ca(2+) chelator, BAPTA-AM, or transfection with antisense oligonucleotides for NADPH oxidase subunits p22(phox) and p 47(phox) inhibited cerulein-induced ROS production, translocation of NADPH oxidase cytosolic subunits p 47(phox) and p 67(phox) to the membrane, and the expression of apoptotic genes and apoptotic indices, as compared to the cells without treatment and those transfected with the corresponding sense oligonucleotides. These results indicate that NADPH oxidase may mediate ROS-induced apoptosis in pancreatic acinar cells in a Ca(2+)-dependent manner.

Oral allopurinol does not prevent the frequency or the severity of post-ERCP pancreatitis

BACKGROUND

Pancreatitis is the most common major complication of ERCP. Efforts have been made to identify pharmacologic agents capable of reducing its incidence and severity. The aim of this trial was to determine whether prophylactic allopurinol, an inhibitor of oxygen-derived free radical production, would reduce the frequency and severity of post-ERCP pancreatitis. Methods A total of 701 patients were randomized to receive either allopurinol or placebo 4 hours and 1 hour before ERCP. A database was prospectively collected by a defined protocol on patients who underwent ERCP. Standardized criteria were used to diagnose and grade the severity of postprocedure pancreatitis.

RESULTS

The groups were similar with regard to patient demographics and to patient and procedure risk factors for pancreatitis. The overall incidence of pancreatitis was 12.55%. It occurred in 46 of 355 patients in the allopurinol group (12.96%) and in 42 of 346 patients in the control group (12.14%; p = 0.52). The pancreatitis was graded mild in 7.89%, moderate in 4.51%, and severe in 0.56% of the allopurinol group, and mild in 6.94%, moderate in 4.62%, and severe in 0.58% of the control group. There was no significant difference between the groups in the frequency or the severity of pancreatitis.

CONCLUSIONS

Prophylactic oral allopurinol did not reduce the frequency or the severity of post-ERCP pancreatitis.

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.

High-dose allopurinol for prevention of post-ERCP pancreatitis: a prospective randomized double-blind controlled trial

BACKGROUND

Pancreatitis is the most common major complication of diagnostic and therapeutic ERCP. Allopurinol, a xanthine oxidase inhibitor that blocks generation of oxygen-derived free radicals, potentially may prevent post-ERCP pancreatitis. This study assessed the efficacy of high-dose oral allopurinol for prevention of post-ERCP pancreatitis.

METHODS

A prospective, double-blind, placebo-controlled trial was conducted in 250 patients undergoing ERCP. Patients were randomized to receive allopurinol (600 mg) or placebo orally at 15 and 3 hours before the procedure. Patients were clinically evaluated, and serum amylase levels were determined before ERCP and at 6 and 24 hours thereafter. Standardized criteria were used to diagnose and to grade the severity of post-ERCP pancreatitis.

RESULTS

A total of 243 patients were included in the analysis. The two groups were similar with regard to age; gender; underlying disease; indication for treatment; ERCP findings; and type of treatment, except for biliary sphincterotomy. Only 43 patients in the allopurinol group underwent biliary sphincterotomy vs. 87 in the placebo group ( p < 0.001). The frequency of acute pancreatitis was significantly lower in the allopurinol vs. the placebo group in the final multinomial regression analysis: allopurinol group, 4/125 (3.2%), with all 4 cases graded as mild, vs. placebo group, 21/118 (17.8%), of which 8/118 (6.8%) were graded as mild, 11/118 (9.3%) as moderate, and 2/118 (1.6%) as severe with fatal outcome ( p < 0.001). The protective effect of allopurinol was also apparent in the diagnostic ERCP and the biliary sphincterotomy subgroups when the frequency of post-ERCP pancreatitis was analyzed after stratification by procedure. The mean duration of hospitalization for pancreatitis was significantly shorter in the allopurinol compared with the placebo group (2.5 vs. 5.67 days; p < 0.001).

CONCLUSIONS

Pretreatment with high-dose, orally administered allopurinol decreases the frequency of post-ERCP pancreatitis. Despite the promising results of this prospective, randomized trial, further studies are needed to verify these observations before allopurinol can be recommended for routine clinical use.

Natural beta-carotene for the prevention of post-ERCP pancreatitis

OBJECTIVE

Endoscopic retrograde cholangiopancreatography (ERCP) is a commonly used procedure. Pancreatitis is its most common complication. As the injury may be mediated by oxidative stress, it could be ameliorated by antioxidants.

METHODS

We conducted a double-blind trial, giving the patients a single dose of natural beta-carotene or placebo, 12 hours prior to procedure, and monitoring them for 24 hours post-procedure for procedure complications, antioxidant levels, and plasma oxidation.

RESULTS

The overall incidence of acute pancreatitis according to our definition was 9.6%. The incidence of pancreatitis was not significantly different between the beta-carotene group (10%) and the placebo group (9.4%). Four patients in the placebo group had severe pancreatitis (2.22%), but none in the beta-carotene group. This difference is statistically significant.

CONCLUSION

We did not see a reduction in the incidence of post-ERCP pancreatitis, but there may be some protective effect of treatment with beta-carotene regarding the severity of disease.

Administration of hyaluronic acid and chondroitin-4-sulfate limits endogenous antioxidant depletion and reduces cell damage in experimental acute pancreatitis

Several reports have described a loss of endogenous antioxidants and molecular oxidative damage during acute pancreatitis. Since hyaluronic acid and chondroitin-4-sulfate possess antioxidant properties, the effect of the administration of these glycosaminoglycans in a cerulein-induced acute pancreatitis in rats was investigated. Cerulein administration produced pancreatic edema and a marked increase in serum lipase and amylase activity; induced a severe depletion of reduced glutathione, catalase, and superoxide dismutase levels; primed lipid peroxidation; and promoted neutrophil intervention. Intraperitoneal pretreatment of rats with hyaluronic acid or chondroitin-4-sulfate or with both compounds ameliorated pancreatic cell conditions; restored the endogenous antioxidants reduced glutathione, catalase and superoxide dismutase; limited cell membrane peroxidation; and reduced neutrophil activation. Our data confirm the antioxidant activity of these 2 glycosaminoglycans.

Alpha-melanocyte stimulating hormone has beneficial effects on cerulein-induced acute pancreatitis

We investigated the effect of alpha-melanocyte stimulating hormone (alpha-MSH) on cerulein induced acute pancreatitis in rats. alpha-MSH treatment (50 microg per rat, intraperitoneally) prior to cerulein reduced the plasma amylase level, pancreatic weight, pancreatic myeloperoxidase activity and the severity of the lesions microscopically. These data suggest that alpha-MSH has a protective effect on cerulein-induced acute pancreatitis and this effect could be attributed, at least in part, to decreased tissue leukocyte infiltration and thus, to decreased pro-inflammatory cytokine production and/or oxygen- and nitrogen-derived reactive metabolite release.

Nutrition support during acute pancreatitis

Studies have shown that protein catabolism increases by 80% and energy expenditure by 20% in acute pancreatitis, indicating that nutritional requirements are elevated. Other studies have associated the resolution of negative nitrogen balance by nutrition support with improved outcome. Consequently, the need for effective nutrition is one cornerstone of management of acute pancreatitis. Concerns that feeding may exacerbate the disease process by stimulating the synthesis of proteolytic enzymes in the acinar cell and perpetuating autolysis has led to the widespread use of total parenteral nutrition (TPN) and bowel rest. Unfortunately, the use of TPN in clinical practice has been associated with major metabolic and infective complications, possibly because 1). patients with acute pancreatitis are intolerant of glucose due to coexistent pancreatic endocrine dysfunction and 2). the disease causes immune suppression. This has led to the search for alternatives. Based on physiologic studies, infusion of nutrients into the distal jejunum bypasses the stimulatory effect of feeding on pancreatic secretion. Many controlled trials have compared TPN with jejunal feeding. No study has shown that jejunal feeding exacerbates the disease. Further, jejunal feeding is associated with fewer infectious and metabolic complications. These observations and the fact that enteral feeding is one-tenth the cost of TPN has resulted in the general acceptance of jejunal feeding as the preferred mode for maintaining nutrition in patients with acute pancreatitis.

Suppression of cerulein-induced cytokine expression by antioxidants in pancreatic acinar cells

Reactive oxygen species (ROS) has been considered to be an important regulator in the development and pathogenesis of pancreatitis and an activator of the transcription factor, nuclear factor-kappaB (NF-kappaB), regulating inflammatory cytokine gene expression. NF-kappaB activation was demonstrated in cerulein pancreatitis, which rapidly induces an acute, edematous form of pancreatitis. This study aimed to investigate whether cerulein induced ROS generation, lipid peroxide and hydrogen peroxide production, NF-kappaB activation, and expression of cytokines (IL-1beta, IL-6) in pancreatic acinar cells. An additional aim was to establish whether these alterations were inhibited by antioxidants such as glutathione, superoxide dismutase, and catalase and an inhibitor of NF-kappaB activation, pyrrolidine dithiocarbamate (PDTC). To determine the possible interactions of the antioxidants and PDTC with cerulein-induced signaling, Ca2+ signal and amylase release were monitored in the pancreatic acinar cells treated with cerulein in the presence or absence of either the antioxidants or PDTC. The results showed that cerulein generated ROS and increased lipid peroxide and hydrogen peroxide production in the acinar cells, as determined by dichlorofluorescein diacetate dye. This resulted in NF-kappaB activation and the induction of cytokine gene expression in the cells. The cerulein-induced NF-kappaB activation was in parallel to IkappaBalpha degradation. Cerulein also induced Ca2+ signals and amylase release in acinar cells. Both antioxidants (glutathione, superoxide dismutase, catalase) and PDTC inhibited the cerulein-induced, oxidant-mediated alterations but did not affect the cerulein-evoked Ca2+ signals and amylase release in acinar cells. In conclusion, ROS, generated by cerulein, activates NF-kappaB, resulting in the up-regulation of inflammatory cytokine gene expression in acinar cells. NF-kappaB inhibition by scavenging ROS might alleviate the inflammatory response in pancreatic acinar cells by suppressing cytokine gene expression.

Minor role of oxidative stress during intermediate phase of acute pancreatitis in rats

Reactive oxygen species have been implicated in the pathogenesis of acute pancreatitis. Few studies have focused on the loss of endogenous antioxidants and molecular oxidative damage. Two acute pancreatitis models in rats; taurocholate (3% intraductal infusion) and cerulein (10 microg/kg/h), were used to study markers of oxidative stress: Glutathione, ascorbic acid, and their oxidized forms (glutathione disulfide and dehydroascorbic acid), malondialdehyde, and 4-hydroxynoneal in plasma and pancreas, as well as 7-hydro-8-oxo-2'-deoxyguanosine in pancreas. In both models, pancreatic glutathione depleted by 36-46% and pancreatic ascorbic acid depleted by 36-40% (p <.05). In the taurocholate model, plasma glutathione was depleted by 34% (p <.05), but there were no significant changes in plasma ascorbic acid or in plasma and pancreas dehydroascorbic acid, malondialdehyde, and 4-hydroxynoneal, and no significant changes in the pancreas glutathione disulfide/glutathione ratio. While pancreas glutathione disulfide/glutathione ratio increased in the cerulein model, there were no significant changes in plasma glutathione, plasma, or pancreas ascorbic acid, dehydroascorbic acid, 4-hydroxynoneal, and malondialdehyde, or in pancreas 7-hydro-8-oxo-2'-deoxyguanosine. Reactive oxygen species have a minor role in the intermediate stages of pancreatitis models.

Role of oxidative stress in the pathogenesis of caerulein-induced acute pancreatitis

In the last decade, the role of oxidative stress has been extensively evaluated in different experimental models of acute pancreatitis. This review shows that there is strong evidence that this stress occurs as an early phenomenon in pancreatic tissue in the course of caerulein-induced acute pancreatitis. Oxidative stress was documented in pancreatic tissue by means of methods showing generation of reactive oxygen species (e.g., chemiluminescence) and accumulation of products of reactive oxygen species-mediated lipid peroxidation. with concomitant depletion of enzymatic and low molecular weight antioxidants. Features of acinar cell injury and inflammation, especially pancreatic edema, show a marked improvement following treatment with a broad spectrum of antioxidants, platelet activating factor antagonists, or donors of nitric oxide (NO). Unfortunately, in most cases these beneficial effects are temporary and generally restricted to an early phase of the disease. However, results of well-designed clinical trials should finally evaluate the importance of oxidative stress-oriented treatment in acute pancreatitis in humans.

Alcohol and the pancreas

Alcoholic pancreatitis is a major, often lethal complication of alcohol abuse. Until recently it was generally accepted that alcoholic pancreatitis was a chronic disease from the outset. However, there is now emerging evidence in favour of the necrosis-fibrosis hypothesis that alcoholic pancreatitis begins as an acute process and that repeated acute attacks lead to chronic pancreatitis, resulting in exocrine and endocrine failure. Over the past 10-15 years, the focus of research into the pathogenesis of alcoholic pancreatitis has shifted from possible sphincteric and ductular abnormalities to the acinar cell itself which has increasingly been implicated as the initial site of injury. Recent studies have shown that the acinar cell can metabolize alcohol at rates comparable to those observed in hepatocytes. In addition, it has been demonstrated that alcohol and its metabolites exert direct effects on the pancreatic acinar cell which may promote premature digestive enzyme activation and oxidant stress. The challenge remains to identify predisposing and triggering factors in this disease.

An ultrastructural study to investigate the effect of allopurinol on cerulein-induced damage to pancreatic acinar cells in rat

CONCLUSION

Subcellular organelles and membranes were the structures most protected by allopurinol, indirectly demonstrating their role of main and early target of oxygen-derived free radicals in the pathogenesis of acute pancreatitis.

BACKGROUND

The present work evaluates the ultrastructural changes during cerulein-induced acute pancreatitis in rat, with and without treatment with allopurinol.

METHODS AND RESULTS

Supramaximal doses of cerulein, injected intraperitoneally (50 microg/kg) twice, at 1-h interval, caused severe subcellular alterations, including zymogen distribution, pathological vacuoles, and damage to organelles and membranes. Cotreatment (40 mg/kg ip twice with 1-h interval; n = 10 rats) and, most of all, pretreatment (40 mg/kg ip allopurinol, 1 h; 20 mg/kg ip allopurinol + 50 microg/kg ip cerulein, 30 min; 40 mng/kg ip allopurinol, 30 min; 50 microg/kg ip cerulein; n = 10 rats) with allopurinol showed significant morphological improvement.

Release of nonesterified fatty acids during cerulein-induced pancreatitis in rats

During acute pancreatitis, data obtained in vitro suggest that pancreatic lipase, acting on circulating or tissular triglycerides, might generate nonesterified fatty acids (NEFA) that could promote pancreatic and fat tissue necrosis. This work determined whether NEFA were actually produced in vivo in pancreatic tissue and in blood during cerulein-induced pancreatitis in rats. Intraperitoneal injections of cerulein induced pancreatitis. To promote the possible NEFA release by pancreatic lipase, a venous infusion of human very low density lipoprotein (VLDL) was used to cause hypertriglyceridemia. NEFA were measured in portal and aortic blood and in tissue extracts prepared from pancreas homogenates. NEFA did not increase either in peripheral or in portal blood. In pancreatic tissue, NEFA levels did not differ from controls. The major hypertriglyceridemia produced by human VLDL intravenous infusion neither altered the course of the disease nor promoted plasma NEFA release. The role commonly attributed to NEFA in acute pancreatitis seems questionable.

Oxidative stress in rodent closed duodenal loop pancreatitis

CONCLUSION

Production of excited oxygen species is earlier in the liver than in the pancreas and could contribute to damage in a reflux model. Treatment with SOD could attenuate 59% light emission in pancreas, but did not modify serum enzyme levels or pancreatic edema, resulting as an insufficient isolated therapy. Unexpectedly, it was found an increased plasma antioxidant capacity that was related to total bilirubin levels, and declined at late stages probably denoting other circulating antioxidant consumption.

BACKGROUND

Oxidative stress has been shown to play a role in different models of acute pancreatitis, although it has not been studied in the severe necrohemorrhagic model produced by closed duodenal loop pancreatitis.

METHODS

We studied Sprague Dawley female rats in two groups: a closed duodenal loop pancreatitis group and a control, sham-operated group. In order to evidence the oxygen excited species production, in situ spontaneous chemiluminescence from living and naturally perfused pancreas and liver was measured at 0, 0.5, 1.5, 3, 6, 12, and 24 h after the duodenal ligature. Blood pancreatic amylase and aminotransferases levels were determined as expression of tissue damage in pancreas and liver. At the same time, plasma antioxidant capacity was measured by the peroxyl radical trapping capability of plasma samples compared to that of Trolox (synthetic analog of vitamin E), and results are expressed as Trolox equivalence. Bovine superoxide dismutase (SOD) was administered to attenuate oxygen free radicals activity at the beginning of the peroxidation chain and also as a therapeutic tool.

RESULTS

The experimental procedure induced a severe pancreatitis, as evidenced by pancreatic enzymes that rose markedly in the early hours of disease and remained heightened throughout the experiment. The results show early light emission from the liver at 3 h and peak levels at 12 h, whereas in the pancreas, luminescence increased at 6 h and doubled later at 12 h, both returning to control levels at 24 h.

Nonesterified fatty acids in acute cerulein-induced pancreatitis in the rat. Are they really deleterious in vivo?

During acute pancreatitis, experimental data obtained in vitro suggested that pancreatic lipase generates nonesterified fatty acids (NEFA), noxious for acinar cells, by hydrolysis of pancreatic or circulating triglycerides. The purpose of this work was to determine whether experimentally induced high plasma NEFA levels do indeed aggravate in vivo cerulein-induced pancreatitis. Anesthetized Sprague-Dawley rats received cerulein and were simultaneously infused intravenously with either saline or a triglyceride + heparin mixture (TGH) in order to increase the amount of circulating NEFA. Plasma NEFA increased about fourfold (3.02 +/- 0.28 mumol/liter) in animals infused with TGH with respect to controls (0.75 +/- 0.05 mumol/liter). In rats receiving cerulein + TGH, pancreatic enzyme levels in plasma, ascites, and histological alterations of the pancreas did not differ from those observed in the rats receiving cerulein + saline. There was less macroscopic pancreatic edema (P < 0.01) in the cerulein + TGH group than in the cerulein + saline group. Separate infusion of either heparin alone or of triglycerides alone had no effect. We conclude that high levels of circulating NEFA do not aggravate cerulein pancreatitis in rats and may even induce a protective effect.

Effect of antioxidant treatment in rats with acute hemorrhagic pancreatitis

The purpose of this study was to evaluate the effect of free radical ablation therapy in acute hemorrhagic pancreatitis. Acute pancreatitis was induced in 64 rats by retrograde injection of 5% sodium taurocholate. Thirty animals were pretreated with 100,000 units/kg/hr of superoxide dismutase (SOD) and 400,000 units/kg catalase within the first 3 hr. After 0.5, 3.5, and 12 hr of observation time, serum enzymes and the tissue content of conjugated dienes, malondialdehyde, reduced and oxidized glutathione, as well as ATP, ADP and AMP were measured. In addition, tissue samples were examined by light microscopy. Untreated rats (N = 34) developed within 12 hr an acute hemorrhagic necrotizing pancreatitis with a concomitant increase in serum enzyme levels and a decrease in reduced glutathione and ATP. Within the 12-hr observation period, 57% of the animals died. Scavenger treatment improved the tissue damage and attenuated the increase of the serum enzyme levels and the decrease in reduced glutathione and ATP. Moreover, the lethality rate was significantly lower. Oxygen radicals seem to be instrumental for the development of acute hemorrhagic pancreatitis. Thereby, antioxidant treatment reduces tissue damage, biochemical alterations and extrapancreatic complications, thus improving the final outcome.

Oxygen free radicals and acute pancreatitis: fact or fiction?

The effect of oxygen free radical suppression was studied in the taurocholate model of acute pancreatitis in the rat using systemic allopurinol, superoxide dismutase (S.O.D.) and catalase. None of the treatments were beneficial which suggests that oxygen free radical suppression is unlikely to be clinically beneficial in acute pancreatitis.

Protection by nitecapone against sodium taurocholate-induced damage to cultured gastric cells

The goal of this study was to observe if nitecapone protected against taurocholate-induced damage in primary cultured rat gastric mucosal cells, as well as in a well-differentiated human gastric epithelial cell line (MKN 28). Prostaglandins were measured to analyze the protection mechanism. In primary rat gastric mucosal cell culture, nitecapone 125-250 microM protected the cells significantly against damage induced by sodium taurocholate, increasing cell viability by 31-38%. In the human gastric epithelial cell line, in which mitochondrial activity was measured as an indication of cell viability, nitecapone (62.5-250 microM) protected the cells against sodium taurocholate-induced damage by 12-20%. Prostaglandin E2, thromboxane B2, and 6-keto-prostaglandin F1 alpha measurements in the primary cultured rat gastric mucosal cells showed that nitecapone (125 microM and 250 microM) significantly stimulated prostaglandin E2 production (84.7% and 61.0%, respectively), and inhibited thromboxane B2 formation (50% at 250 microM), while the 6-keto-prostaglandin F1 alpha formation was unaffected. Nitecapone had no effect on prostaglandin E2 production in the MKN 28 epithelial cell line. Indomethacin or aspirin, at concentrations that did not affect cell viability, antagonized the stimulative effect of nitecapone on prostaglandin E2 formation in the primary cultured rat gastric mucosal cells. Although the prostaglandin E2 synthesis was blocked, nitecapone still protected against cell damage induced by taurocholate. These results demonstrated the direct and efficacious protection of nitecapone on gastric cell level and suggest that the "cytoprotection" by nitecapone against taurocholate may not be mediated through the mechanism of stimulated synthesis of prostaglandin E2.

Glutathione monoethyl ester ameliorates caerulein-induced pancreatitis in the mouse

Studies in animal models suggest that oxygen radicals may be important in the pathogenesis of acute pancreatitis. Because glutathione is an essential component of the defense against radical-mediated cellular injury, we investigated whether pancreatic glutathione content is influenced by inducing acute pancreatitis and whether augmenting the intracellular supply of glutathione would alter the course of pancreatitis. Caerulein, a decapeptide cholecystokinin analogue, induces acute necrotizing pancreatitis in mice when given in high doses (50 micrograms/kg per h) over a period of 6 h. The pancreatic glutathione content (total, GSH + GSSG) in mice treated with high-dose caerulein fell to 17% of normal within 4 h of beginning caerulein and recovered toward normal after discontinuing caerulein treatment. Mice treated with glutathione monoethyl ester (20 mmol/kg 1 h before caerulein, 10 mmol/kg 3 and 7 h after starting caerulein) were found to have blunted depletion of pancreatic glutathione, diminished histologic evidence of pancreatitis (necrosis, inflammation, and vacuolization), and lower serum amylase values compared with mice treated with caerulein alone. These findings suggest that the profound depletion of pancreatic glutathione caused by hyperstimulation of the pancreas with caerulein is critically important in the pathogenesis of acute caerulein-induced pancreatitis.

The role of oxygen radicals in experimental acute pancreatitis

Oxygen-derived free radicals mediate an important step in the initiation of experimental acute pancreatitis. Thereby, it seems that these reactive oxygen metabolites are generated at an early stage of disease. The source of the enhanced production of oxygen radicals still remains unclear. Experimentally, the efficiency of scavenger treatment varied between different models, whereby these differences depended on the experimental model and not on the form of pancreatitis which was induced. Most studies pretreated the experimental animals before inducing acute pancreatitis. This does not mirror the clinical reality, since patients are admitted to the hospital after onset of the disease. It was shown in Cerulein pancreatitis, however, that scavenger treatment also mitigated the pancreatic tissue damages after induction of acute pancreatitis. Moreover, antioxidant treatment also attenuated the extrapancreatic complications, thus improving the final outcome of the disease. The first indirect observations also suggest that in human acute recurrent and chronic pancreatitis, oxygen free radicals are generated and add to the damages seen. Therefore, well-defined controlled clinical studies with patients suffering from acute pancreatitis are needed to validate the role of oxygen radicals in this disease.

The role of oxygen-derived free radicals in two models of experimental acute pancreatitis: effects of catalase, superoxide dismutase, dimethylsulfoxide, and allopurinol

The role of oxygen-derived free radicals was evaluated in two models of experimental acute pancreatitis by testing the effects of agents which either reduce oxygen-derived free radical generation or scavenge those free radicals. Those agents (catalase, superoxide dismutase, polyethylene glycol-superoxide dismutase, dimethylsulfoxide, and allopurinol) were evaluated using the choline-deficient ethionine-supplemented diet-induced model of acute hemorrhagic pancreatic necrosis and the supramaximal caerulein stimulation model of acute interstitial edematous pancreatitis. In both models, the only effect associated with administration of the test agents was a reduction in the degree of pancreatic edema. These results suggest that oxygen-derived free radicals may play an important role in the development of pancreatic edema during pancreatitis but that those free radicals do not play an important role in the development of acinar cell injury.