Effect of melatonin on the severity of L-arginine-induced experimental acute pancreatitis in rats

Ameliorative effects of the melatonin on some cytokine levels, NF-κB immunoreactivity, and apoptosis in rats with cerulein-induced acute pancreatitis

Objectives

Investigating the ameliorative effects of melatonin on cytokine levels, apoptosis, and NF-κB immunoreactivity in rats with cerulein-induced acute pancreatitis.

Materials and Methods

Thirthy-two Wistar Albino rats were divided into four groups: Control group which didn't undergo acute pancreatitis induction and was left without treatment, pancreatitis group in which the acute pancreatitis was induced by 2 successive intraperitoneal doses of cerulein at a 2-hour interval (50 µg/kg and then 25 µg/kg), melatonin-treated pancreatitis group which was intraperitoneally administrated with 50 mg/kg of melatonin, 30 min before each cerulein injection, and melatonin group which was intraperitoneally administrated with 2 successive doses of melatonin (50 mg/kg each) at a 2-hour interval. Pancreatic tissue and blood samples were taken from animals of all groups. IL-1β, TNF-α, and IL-10 levels were determined in blood samples. Apoptosis was determined by the TUNEL assay and the NF-κB was detected immunohistochemically in acinar cells of the exocrine pancreatic portion.

Results

IL-1β, TNF-α, and IL-10 levels in the acute pancreatitis group were significantly increased when compared to the control negative group. IL-1β and TNF-α levels in the melatonin-treated pancreatitis group were significantly lower than those of the acute pancreatitis group. While number of apoptotic cells and percentage of NF-κB immunopositive cells in the acute pancreatitis group were significantly increased compared to other groups and it was observed that these parameters were significantly reduced in the melatonin-treated pancreatitis group compared to the acute pancreatitis group.

Conclusion

These findings suggest that melatonin administration can significantly reduce the severity of acute pancreatitis in rats.

Genistein attenuated oxidative stress, inflammation, and apoptosis in L-arginine induced acute pancreatitis in mice

Aim

Acute pancreatitis is a common and potentially serious condition. However, a specific treatment for this condition is still lacking. Genistein, with its anti-oxidant and anti-inflammatory effects, could possibly be used to tackle the underlying pathophysiology of acute pancreatitis. Therefore, the aim of this study was to investigate the effects of genistein on oxidative stress, inflammation, and apoptosis in acute pancreatitis induced by L-arginine in mice.

Methods

Twenty-four male ICR mice were equally divided into 4 groups: Control (Con); Acute pancreatitis (AP) group: Two doses of i.p. 350 mg/100 g body weight (BW) of L-arginine were administered 1 h apart; AP and low-dose genistein (LG) group: mice were given i.p. injection of 10 mg/kg genistein 2 h prior to L-arginine injection followed by once-daily dosing for 3 days; and AP and high-dose genistein (HG) group: mice were given 100 mg/kg genistein with the similar protocol as the LG group. Pancreatic tissue was evaluated for histopathological changes and acinar cell apoptosis, malondialdehyde (MDA) levels, immunohistochemical staining for myeloperoxidase (MPO), nuclear factor-kappa beta (NF-kB), and 4-hydroxynonenal (4-HNE). Serum levels of amylase (AMY), c-reactive protein (CRP), and interleukin (IL)-6 were measured.

Results

Significant increases in the degree of acinar cell apoptosis, pancreatic MDA, serum IL-6 and amylase, MPO, NF-kB and 4-HNE positivity were observed in the AP group. All these parameters declined after low- and high-dose genistein treatment. Severe pancreatic inflammation, edema, and acinar cell necrosis were observed in the AP group. Significant improvement of histopathological changes was seen in both low- and high-dose genistein groups. There were no significant differences in any parameters between low and high doses of genistein.

Conclusion

Genistein could attenuate the severity of histopathological changes in acute pancreatitis through its anti-oxidant, anti-inflammatory, and anti-apoptotic properties.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03689-9.

Melatonin protects sheep endometrial epithelial cells against lipopolysaccharide-induced inflammation in vitro

Melatonin has known anti-inflammatory effects. However, how melatonin protects sheep endometrial epithelial cells from inflammation remains unknown. In this study, we investigated the melatonin synthetase AANAT and HIOMT, and melatonin membrane receptors MT1 and MT2 distribution in sheep uterus. Using lipopolysaccharide (LPS)-stimulated sheep endometrial epithelial cells as an in vitro inflammation model. The results showed that melatonin attenuated the expression of inflammatory factors in a concentration-response manner. Melatonin also inhibited the LPS-stimulated phosphorylation of ERK1/2, JNK and NF-κB p65. This attenuation was partially blocked by luzindole (a nonspecific MT1 and MT2 inhibitor) or 4P-PDOT (specific MT2 inhibitor). In addition, the above inhibition of melatonin was abolished by the PI3K/AKT pathway inhibitor LY294002. It was concluded that melatonin had an inhibitory effect on LPS-induced endometrial epithelial cell inflammation in sheep, which was mediated by the activation of the PI3K/AKT pathway via melatonin receptors.

Granny Smith Apple Extract Lowers Inflammation and Improves Antioxidant Status in L-arginine-induced Exocrine Pancreatic Dysfunction in Rats

Objectives

Granny Smith is a cultivated hybrid variety of apple with a high antioxidant content relative to all other species of apple. Acute pancreatitis (AP) is an instantly emerging inflammatory condition with a high mortality rate. The preferred treatment is restricted to symptomatic relief and supportive care. The present study was undertaken to evaluate the favorable effects of Granny Smith apple extract (GSAE) as a prophylactic treatment for L-arginine-induced AP in rats.

Materials and Methods

Male Sprague Dawley rats were divided in to five groups (n=6): Normal control (saline), disease control (a single dose of L-arginine 2.5 g/kg I.P.), positive control (pelatonin 10 mg/kg I.P.), and GSAE I and II (200 mg/kg and 400 mg/kg, orally, respectively). All groups were treated for 7 days. At the end of the study, blood samples were collected from the retro-orbital plexus, serum separated, and subjected to estimation of biomarker enzymes such as amylase, lipase, antioxidant enzymes, etc. The animals were then sacrificed, and the pancreas was isolated and subjected to estimation of tissue biomarkers, DNA fragmentation assay, and histopathological studies.

Results

Serum levels of amylase and lipase were significantly (p<0.001) reduced in L-arginine-treated rats. Similar results were also observed with tissue inflammatory markers such as malondialdehyde, nitrate, etc. There was a dramatic increase (p<0.001) in the overall antioxidant enzyme levels when compared with disease control rats. Histopathological examination of pancreatic tissue showed an intact structural feature of acinar cells in the extract-treated group of rats, which was further in pact with the intact DNA found in the DNA fragmentation assay.

Conclusion

Thus, GSAE treatment was found to be beneficial in lowering the inflammatory conditions of AP by improving the overall antioxidant levels, and a further investigation into its exact molecular mechanism is needed.

Effects of sildenafil citrate on pancreatic and lung complications in an experimental L-arginine-induced acute pancreatitis model

Aim

In this study, we aimed to investigate the effects of sildenafil citrate on acute pancreatitis and pulmonary complications of the disease.

Material and methods

In this study, we used 21 male Wistar-Albino rats weighing between 185 and 230 g. The rats were divided into 3 groups. Group 1 rats (control group, n = 7) were administered intraperitoneal 0.9% NaCl injection. Group 2 (study group, n = 7) and Group 3 (treatment group, n = 7) rats were given 100 mg/100 gr L-arginine twice, with an interval of 1 h to create acute pancreatitis. Group 3 was also administered intraperitoneal 10 mg/kg/day sildenafil citrate in 2 equal doses, 30 min and 12 h after creation of AP. The pancreas and lungs of all rats were stained with haematoxylin and eosin and examined histopathologically. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), interleukin (IL) 1α (IL-1α), IL-6, tumor necrosis factor α (TNF-α), nitric oxide (NO) and ADMA levels were measured in blood samples.

Results

In the treatment group, levels of amylase, AST, ALT, LDH, IL-1, IL-6, TNF-α, and NO were lower. In addition, pancreas and lung oedema, and perivascular inflammation were significantly less on histopathological examination when compared to the study group (p < 0.001). The ADMA level was significantly higher in the treatment group when compared to the control and study groups. There was no acinar cell necrosis or haemorrhage in the treatment group. However, the difference was not regarded as statistically significant because sufficient acinar cell necrosis and haemorrhage could not be created in the study group.

Conclusions

Sildenafil citrate significantly decreases various biochemical and histopathological changes in the early phase of acute pancreatitis and protects pancreatic tissue.

Experimental Acute Pancreatitis Models: History, Current Status, and Role in Translational Research

Acute pancreatitis is a potentially severe inflammatory disease that may be associated with a substantial morbidity and mortality. Currently there is no specific treatment for the disease, which indicates an ongoing demand for research into its pathogenesis and development of new therapeutic strategies. Due to the unpredictable course of acute pancreatitis and relatively concealed anatomical site in the retro-peritoneum, research on the human pancreas remains challenging. As a result, for over the last 100 years studies on the pathogenesis of this disease have heavily relied on animal models. This review aims to summarize different animal models of acute pancreatitis from the past to present and discuss their main characteristics and applications. It identifies key studies that have enhanced our current understanding of the pathogenesis of acute pancreatitis and highlights the instrumental role of animal models in translational research for developing novel therapies.

Melatonin protects against lipopolysaccharide-induced epididymitis in sheep epididymal epithelial cells in vitro

Melatonin has protective effects against inflammation but its role in epididymitis is unknown. We addressed this in the present study using lipopolysaccharide (LPS)-stimulated sheep epididymal epithelial cells as an in vitro inflammation model. We found that interleukin (IL)-1β, IL-6, tumor necrosis factor α, and cyclooxygenase (COX)-2 mRNA levels; COX-2 and Toll-like receptor (TLR)-4 protein levels; and nuclear factor (NF)-κB p65 phosphorylation were increased by LPS treatment. These effects were reversed in a dose-dependent manner by melatonin (10^-11-10^-7 M). Quantitative reverse transcription PCR and immunofluorescence analyses showed that the melatonin receptors MT1 and MT2 were expressed in sheep epididymal epithelial cells. The inhibitory effect of melatonin on inflammation was abrogated by the MT1 and MT2 receptor antagonist luzindole and the MT2 ligand 4-phenyl-2-propanamide tetraldehyde. Thus, melatonin exerted anti-inflammatory effect in epididymal epithelial cells by inhibiting TLR4/NF-κB signaling, suggesting its potential as an effective drug for the treatment of epididymitis in sheep.

Pre- vs. post-treatment with melatonin in CCl4-induced liver damage: Oxidative stress inferred from biochemical and pathohistological studies

AIMS

The present study was designed to compare the ameliorating potential of pre- and post-treatments with melatonin, a potent natural antioxidant, in the carbon tetrachloride-induced rat liver damage model by tracking changes in enzymatic and non-enzymatic liver tissue defense parameters, as well as in the occurring pathohistological changes.

MAIN METHODS

Rats from two experimental groups were treated with melatonin before and after CCl₄ administration, while the controls, negative and positive, received vehicle/melatonin and CCl₄, respectively. Serum levels of transaminases, alkaline phosphates, γ-GT, bilirubin, and albumin, as well as a wide panel of oxidative stress-related parameters in liver tissue, were determined in all experimental animals. Liver tissue specimens were stained with hematoxylin and eosin and further evaluated for morphological changes.

KEY FINDINGS

Both pre- and post-treatment with melatonin prevented a CCl₄-induced increase in serum (ALT, AST, and γ-GT) and tissue (MDA and XO) liver damage markers and a decrease in the tissue total antioxidant capacity, in both enzymatic and non-enzymatic systems. The intensity of pathological changes, hepatocyte vacuolar degeneration, necrosis and inflammatory cell infiltration, was suppressed by the treatment with melatonin.

SIGNIFICANCE

In conclusion, melatonin, especially as a post-intoxication treatment, attenuated CCl₄-induced liver oxidative damage, increased liver antioxidant capacities and improved liver microscopic appearance. The results are of interest due to the great protective potential of melatonin that was even demonstrated to be stronger if applied after the tissue damage.

Effects of Melatonin and Its Analogues on Pancreatic Inflammation, Enzyme Secretion, and Tumorigenesis

Melatonin is an indoleamine produced from the amino acid l-tryptophan, whereas metabolites of melatonin are known as kynuramines. One of the best-known kynuramines is N¹-acetyl-N¹-formyl-5-methoxykynuramine (AFMK). Melatonin has attracted scientific attention as a potent antioxidant and protector of tissue against oxidative stress. l-Tryptophan and kynuramines share common beneficial features with melatonin. Melatonin was originally discovered as a pineal product, has been detected in the gastrointestinal tract, and its receptors have been identified in the pancreas. The role of melatonin in the pancreatic gland is not explained, however several arguments support the opinion that melatonin is probably implicated in the physiology and pathophysiology of the pancreas. (1) Melatonin stimulates pancreatic enzyme secretion through the activation of entero-pancreatic reflex and cholecystokinin (CCK) release. l-Tryptophan and AFMK are less effective than melatonin in the stimulation of pancreatic exocrine function; (2) Melatonin is a successful pancreatic protector, which prevents the pancreas from developing of acute pancreatitis and reduces pancreatic damage. This effect is related to its direct and indirect antioxidant action, to the strengthening of immune defense, and to the modulation of apoptosis. Like melatonin, its precursor and AFMK are able to mimic its protective effect, and it is commonly accepted that all these substances create an antioxidant cascade to intensify the pancreatic protection and acinar cells viability; (3) In pancreatic cancer cells, melatonin and AFMK activated a signal transduction pathway for apoptosis and stimulated heat shock proteins. The role of melatonin and AFMK in pancreatic tumorigenesis remains to be elucidated.

Effects of melatonin on the acute inflammatory response associated with endoscopic retrograde cholangiopancreatography: A randomized, double-blind, placebo-controlled trial

INTRODUCTION

Endoscopic retrograde cholangiopancreatography (ERCP) is associated with an acute inflammatory response and melatonin has a variety of immunomodulatory and antioxidant effects studied experimentally in pancreatobiliary pathology.

AIMS

The aim of our study was to evaluate the effects of peri-procedural administration of melatonin on the inflammatory response and lipid peroxidation associated with ERCP.

METHODS

In this proof-of-concept clinical trial, 37 patients with a high probability of choledocholithiasis were randomized to receive peri-procedure (ERCP) melatonin or placebo. We measured the serum concentration of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), lipid peroxidation, amylase, and liver function tests 24h before and after the procedure.

RESULTS

We found no pre-procedure or post-procedure differences between the melatonin group or the placebo group (P>.05) in the serum concentrations of TNF-alpha (melatonin: 153.8 vs. 149.4ng/m; placebo: 103.5 vs. 107.3ng/ml), IL-6 (melatonin: 131.8 vs. 133.3ng/ml; placebo: 177.8 vs. 197.8ng/ml), or VEGF (melatonin: 157.3 vs. 157.8pg/ml; placebo: 97.3 vs. 97.8pg/ml), or in relation to lipid peroxidation (melatonin: 39.2 vs. 72.3μg/ml; placebo: 66.4 vs. 90.5μg/ml). After ERCP, a significant decrease in the AST, ALT, and total bilirubin levels was found only in the melatonin group (P<.05). The administration of melatonin was safe and tolerable.

CONCLUSIONS

Melatonin is safe and tolerable in patients undergoing ERCP, but it does not appear to affect inflammatory cytokine concentrations or lipid peroxidation.

Effects of Acupuncture at St25 on Inflammatory Mediators and Nuclear Factor κB Activation in a Rat Model of Severe Acute Pancreatitis

Objective

To observe the effect of electroacupuncture (EA) and manual acupuncture (MA) at ST25 on inflammatory mediators and nuclear factor κ-B (NF-κB) activation in rats with sodium taurocholate-induced severe acute pancreatitis (SAP).

Methods

Eighty-eight male Sprague–Dawley rats were randomly divided into four groups: control (sham-operated), SAP, SAP+EA and SAP+MA (n=22 each). A SAP model was established by injecting 3.5% sodium taurocholate 1 mL/kg into the pancreatic duct. In each group, animals were killed at t=3 h (n=7), 6 h (n=7) and 12 h (n=8) after the procedure. Pancreatic expression of NF-κB was examined by immunohistochemical staining. The levels of tumour necrosis factor α (TNF-α) and interleukin 6 (IL-6) in serum were determined by ELISA. Pathological changes in the pancreas were examined microscopically.

Results

Serum levels of TNF-α and IL-6 increased and morphological changes consistent with tissue damage were observed in the pancreas of SAP rats. NF-κB p65 expression was significantly higher in the SAP group than in the sham-operated group (p<0.05). Treatment with acupuncture at ST25 attenuated morphological damage and reduced levels of TNF-α and IL-6 in serum. NF-κB p65 expression was also significantly reduced by acupuncture at ST25 in the pancreas at 6 and 12 h after the procedure (p<0.05). There were no significant differences between the SAP+EA and SAP+MA groups.

Conclusions

Acupuncture at ST25 might have a therapeutic effect on rats with SAP through inhibition of NF-κB expression and a reduction in the release of pro-inflammatory cytokines.

Antioxidants as a treatment for acute pancreatitis: A meta-analysis

OBJECTIVE

To assess the efficacy of antioxidants in acute (AP) pancreatitis.

METHODS

We searched PubMed, Embase and the Cochrane library for all randomized controlled trials (RCT) involving administration of antioxidants in the therapy of AP until February 2012. AP studies were pooled to analyze the effect of antioxidants on hospital stay, mortality, and complications. Subgroup analyses were performed on the use of the antioxidant glutamine.

RESULTS

In total, eleven RCTs were included. Among patients with AP, antioxidant therapy resulted in a borderline significant reduction in hospital stay (mean difference -1.74; 95%CI -3.56 to 0.08), a significant decrease in complications (RR 0.66; 95%CI 0.46-0.95) and a non-significant decrease in mortality rate (RR 0.66; 95%CI 0.30-1.46). Subgroup analyses showed that glutamine significantly reduced complications (RR 0.51; 95%CI 0.34-0.78) and mortality rate (RR 0.33; 95%CI 0.13-0.85).

CONCLUSION

The present meta-analysis shows a possible benefit of glutamine supplementation in patients with acute pancreatitis. However, large randomized trials are needed to confirm these observations.

Vascular endothelial injury and apoptosis in rats with severe acute pancreatitis

We explored mechanisms of vascular endothelial injury that lead to systemic multiple organ failure by detecting the soluble endothelial protein C receptor (sEPCR), von Willebrand factor (vWF), serum nitric oxide (NO), and tumor necrosis factor alpha (TNF-α) and Bcl-2 mRNA and Bax mRNA expression in a severe acute pancreatitis (SAP) rat model. Compared to controls, the levels of TNF-α, vWF, and sEPCR were significantly increased in the experimental group at 12 hours and 24 hours and the NO level was significantly decreased. After 12 hours, the aortic endothelial apoptosis index and Bax mRNA expression in aortic endothelial cells had increased in the experimental group, but Bcl-2 mRNA levels had decreased. All these changes appeared at both 12 h and 24 hours. The results indicated that vascular endothelial injury and apoptosis markers were elevated in SAP. Endothelial injury and increased apoptosis in the experimental group were related to the increased expression of TNF-α.

Recent advances in the investigation of pancreatic inflammation induced by large doses of basic amino acids in rodents

It has been known for approximately 30 years that large doses of the semi-essential basic amino acid L-arginine induce severe pancreatic inflammation in rats. Recently, it has been demonstrated that L-arginine can also induce pancreatitis in mice. Moreover, other basic amino acids like L-ornithine and L-lysine can cause exocrine pancreatic damage without affecting the endocrine parenchyma and the ducts in rats. The utilization of these noninvasive severe basic amino acid-induced pancreatitis models is becoming increasingly popular and appreciated as these models nicely reproduce most laboratory and morphological features of human pancreatitis. Consequently, the investigation of basic amino acid-induced pancreatitis may offer us a better understanding of the pathogenesis and possible treatment options of the human disease.

Oxidative stress in acute pancreatitis: lost in translation?

Oxidative stress has been implicated in the pathogenesis of acute pancreatitis, a severe and debilitating inflammation of the pancreas that carries a significant mortality, and which imposes a considerable financial burden on the health system due to patient care. Although extensive efforts have been directed towards the elucidation of critical underlying mechanisms and the identification of novel therapeutic targets, the disease remains without a specific therapy. In experimental animal models of acute pancreatitis, increased oxidative stress and decreased antioxidant defences have been observed, changes also detected in patients clinically. However, despite the promise of studies evaluating the effects of antioxidants in these model systems, translation to the clinic has thus far been disappointing. This may reflect many factors involved in the design of both preclinical and clinical evaluations of antioxidant therapy, not least the fact that most experimental studies have focussed on pre-treatment rather than post-injury assessment. This review has examined evidence relating to the involvement of oxidative stress in the pathophysiology of acute pancreatitis, focussing on experimental models and the clinical experience, including the experimental techniques employed and potential of antioxidant therapy.

Effects of trimetazidine in acute pancreatitis induced by L-arginine

BACKGROUND

In acute pancreatitis, oxygen free radicals (OFRs) and cytokines have been shown to play a role in the failure of pancreatic microcirculation and the development of local tissue damage. We studied the effects of trimetazidine (TMZ), a potent antioxidant and anti-ischemic agent, on acute pancreatitis.

METHODS

Rats were randomized into 3 groups: a control group (n = 15), a study group (n = 15) in which acute pancreatitis was induced with with L-arginine, and a treatment group (n = 15) in which pancreatitis was induced and treated with TMZ intraperitoneally. The rats were followed for 24 hours. At the 24th hour we determined serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), amylase, lactate dehydrogenase (LDH), interleukin 1-β (IL-1β), interleukin 6 (IL-6) and tumour necrosis factor-α (TNF-α), and the pancreatic tissues were analyzed histopathologically.

RESULTS

The AST (p < 0.001), ALT (p < 0.01), amylase (p < 0.001), LDH (p < 0.01), TNF-α (p < 0.01), IL-1β (p < 0.001) and IL-6 (p < 0.001) levels, and pancreatic tissue edema (p < 0.01), hemorrhage (p < 0.05), acinar cell necrosis (p < 0.001) and level of perivascular inflammation (p < 0.01), were significantly lower in the treatment group than the study group.

CONCLUSION

Trimetazidine markedly decreases biochemical and histopathologic changes during the early stages of acute pancreatitis, thus preserving the pancreas histologically.

Therapeutic effects of electroacupuncture at ST36 acupoint on sodium-taurocholate-induced severe acute pancreatitis

OBJECTIVE

To explore the protective effects and mechanisms of electroacupuncture (EA) at Zusanli (ST36) acupoint in rats with severe acute pancreatitis (SAP).

METHODS

Sixty-six male Sprague-Dawley rats were randomly assigned to three groups of 22 each: a SAP model group (SAP group), a shamoperated group (sham group) and a EA at ST36 acupoint group (EA group). A rat model of SAP was induced by pancreatic duct injection with 3.5% sodium taurocholate. EA was performed at ST36 acupoint for 30 min after induction of SAP and 30 min before sacrificed. The rats were killed at 3 h (n=7), 6 h (n=7) and 12 h (n=8) after operation, and blood samples were taken for the measurement of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and acetylcholine (Ach) by enzyme-linked immunosorbnent assay. The pathological changes of pancreatic tissue, volume of ascites and pancreatic weight/body weight ratio were measured.

RESULTS

The serum concentrations of TNF-α and IL-6 in the EA group were significantly lower than in the SAP group at 3, 6 and 12 h after the operation (p<0.05). Serum Ach in the EA group was significantly higher than in the SAP group at various time points after operation (p<0.05). The other parameters were clearly improved after treatment with EA.

CONCLUSION

EA at ST36 acupoint might have a therapeutic effect in rats with SAP through activating the cholinergic anti-inflammatory pathway.

1,8-cineole (eucalyptol) ameliorates cerulein-induced acute pancreatitis via modulation of cytokines, oxidative stress and NF-κB activity in mice

AIMS

Acute pancreatitis (AP) is an inflammatory condition wherein pro-inflammatory mediators, oxidative stress, and NF-κB signaling play a key role. Currently, no specific therapy exists and treatment is mainly supportive and targeted to prevent local pancreatic injury and systemic inflammatory complications. This study was aimed to examine whether 1,8-cineole, a plant monoterpene with antioxidant and anti-inflammatory properties could ameliorate cerulein-induced acute pancreatitis.

MAIN METHODS

AP was induced in Swiss mice by six one hourly injections of cerulein (50 μg/kg, i.p.). 1,8-cineole (100, 200 and 400mg/kg, p.o.) was administered 1h prior to first cerulein injection, keeping vehicle and thalidomide treated groups as controls. Blood samples were taken 6-h later to determine serum levels of amylase and lipase, and cytokines. The pancreas was removed for morphological examination, myeloperoxidase (MPO) and malondialdehyde (MDA) assays, reduced glutathione (GSH) levels, and for nuclear factor (NF)-κB immunostaining.

KEY FINDINGS

1,8-cineole effectively reduced the cerulein-induced histological damage, pancreatic edema and NF-κB expression, levels of MPO activity and MDA, and replenished the GSH depletion. Cerulein increased serum levels of amylase and lipase, and pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 were also decreased by 1,8-cineole pretreatment, similar to thalidomide, a TNF-α inhibitor. The anti-inflammatory IL-10 cytokine level was, however, enhanced by 1,8-cineole.

SIGNIFICANCE

These findings indicate that 1,8-cineole can attenuate cerulein-induced AP via an anti-inflammatory mechanism and by combating oxidative stress. Further studies are needed to clearly elucidate its benefits in patients on acute pancreatitis.

Protective effect of melatonin on acute pancreatitis

Melatonin, a product of the pineal gland, is released from the gut mucosa in response to food ingestion. Specific receptors for melatonin have been detected in many gastrointestinal tissues including the pancreas. Melatonin as well as its precursor, L-tryptophan, attenuates the severity of acute pancreatitis and protects the pancreatic tissue from the damage caused by acute inflammation. The beneficial effect of melatonin on acute pancreatitis, which has been reported in many experimental studies and supported by clinical observations, is related to: (1) enhancement of antioxidant defense of the pancreatic tissue, through direct scavenging of toxic radical oxygen (ROS) and nitrogen (RNS) species, (2) preservation of the activity of antioxidant enzymes; such as superoxide dismutase (SOD), catalase (CAT), or glutathione peroxidase (GPx), (3) the decline of pro-inflammatory cytokine tumor necrosis α (TNFα) production, accompanied by stimulation of an anti-inflammatory IL-10, (4) improvement of pancreatic blood flow and decrease of neutrophil infiltration, (5) reduction of apoptosis and necrosis in the inflamed pancreatic tissue, (6) increased production of chaperon protein (HSP60), and (7) promotion of regenerative process in the pancreas. Conclusion. Endogenous melatonin produced from L-tryptophan could be one of the native mechanisms protecting the pancreas from acute damage and accelerating regeneration of this gland. The beneficial effects of melatonin shown in experimental studies suggest that melatonin ought to be employed in the clinical trials as a supportive therapy in acute pancreatitis and could be used in people at high risk for acute pancreatitis to prevent the development of pancreatic inflammation.

Hyperbaric oxygen and N-acetylcysteine treatment in L-arginine-induced acute pancreatitis in rats

BACKGROUND

This study was designed to evaluate the combined effects of hyperbaric oxygen (HBO) and N-acetylcysteine (NAC) on acute necrotizing pancreatitis in rats.

METHODS

Experiments were performed in 50 male Wistar rats, which were divided into five groups (N = 10 for each group). The first group received normal saline (0.9% NaCl) intraperitoneal and served as the control group. In the second group, acute pancreatitis was induced by 3.2-g/kg body weight L-arginine intraperitoneal twice at an interval of 1 hr, which has been shown previously to produce severe necrotizing acute pancreatitis. In the third group, NAC treatment (1000 mg/kg) was given after 1 hr of the induction of acute pancreatitis twice 24 hr apart. In the fourth group, animals received HBO, 6 hr after the induction of pancreatitis twice 12 hr apart. In the fifth group, animals received together NAC as in Group 3 and HBO treatment as in Group 4. Groups 1, 2, and 3 were left under normal atmospheric pressures. Twelve hours after last treatment, the animals were killed by exsanguinations. Blood samples were studied for amylase, calcium, and lactate dehydrogenase (LDH), pancreatic histology, pancreatic tissue malondialdehyde, superoxide dismutase, and glutathione levels.

RESULTS

Acute pancreatitis is reduced by the treatment of NAC, HBO, NAC + HBO. HBO + NAC groups performed statistically the best in preventing L-arginine-induced acute necrotising pancreatitis.

CONCLUSIONS

NAC especially combined with HBO, decreases oxidative stress parameters, serum amylase, calcium, and LDH levels, as well as histopathologic score.

Pinealectomy aggravates acute pancreatitis in the rat

Melatonin, a pineal indoleamine, protects the pancreas against acute damage; however, the involvement of the pineal gland in the pancreatoprotective action of melatonin is unknown. The primary aim of this study was to determine the effects of pinealectomy on the course of acute caerulein-induced pancreatitis (AP) in rats. AP was induced by a subcutaneous infusion of caerulein (25 μg/kg) into pinealectomized or sham-operated animals. Melatonin (5 or 25 mg/kg) was given via intraperitoneal (ip) injection 30 min prior to the induction of AP. The pancreatic content of the lipid peroxidation products malondialdehyde and 4-hydroxynonenal (MDA + 4HNE) and the activity of an antioxidative enzyme, glutathione peroxidase (GSH-Px), were measured in each group of rats. Melatonin blood levels were measured by radioimmunoassay (RIA). In the sham-operated rats, AP was confirmed with histological examination and manifested as pancreatic edema and an increase in the blood lipase level (by 1,500%). In addition, the pancreatic content of MDA+ 4HNE was increased by 200%, and pancreatic glutathione peroxydase (GSH-Px) activity was reduced by 40%. Pinealectomy significantly aggravated the histological manifestations of AP, reduced the GSH-Px activity and markedly augmented the levels of MDA+ 4HNE in the pancreas of rats with or without AP as compared to sham-operated animals. Melatonin was undetectable in the blood of the pinealectomized rats with or without AP. Treatment with melatonin (25 mg/kg, ip) prevented the development of AP in the sham-operated rats and significantly reduced pancreatic inflammation in the animals previously subjected to pinealectomy. In conclusion, pineal melatonin contributes to the pancreatic protection through the activation of the antioxidative defense mechanism in pancreatic tissue as well as its direct antioxidant effects.

Protective role of endogenous melatonin in the early course of human acute pancreatitis

Melatonin plays a protective role in experimental acute pancreatitis (AP) because of its antioxidative, antiinflammatory, and immunomodulatory effects. This study presents the first data on the dynamic changes of endogenous melatonin in the early phase of human AP. Morning (08:00 hr) serum melatonin concentrations were measured by ELISA in 75 patients with AP for the first 5 days after the onset of pain. According to the Atlanta classification, 26 patients suffered a mild AP (MAP). The other 49 developed a severe AP (SAP). Median melatonin concentrations of healthy volunteers were used as a control. Median melatonin level in healthy controls was 18.5 pg/mL. Levels of melatonin were significantly higher in the first 24 hr after onset of disease in patients with MAP compared to those with SAP, 51.2 versus 8.7 pg/mL (P = 0.01). Melatonin values were the same in MAP and SAP during the remainder of the study period. Melatonin concentrations during the first 24 hr after the onset of pain in younger patients (<35 yrs old) were significantly higher than levels in older patients (>35 yrs): 73 versus 8.7 pg/mL (P = 0.01). No correlation existed between melatonin levels and the following parameters: gender, etiology (biliary versus alcohol induced), and histological findings (edematous versus necrotizing versus infected necrosis). High endogenous melatonin serum levels in the first 24 hr after the onset of AP played a protective role and favoured a mild course of the disease in humans, especially in young patients.

Effect of pentoxifylline and/or alpha lipoic acid on experimentally induced acute pancreatitis

Acute pancreatitis is a sudden inflammation of the pancreas that may be life threatening disease with high mortality rates; particularly in presence of systemic inflammatory response and multiple organ failure despite of the conventional antibiotic and symptomatic treatment. Oxidative stress has been shown to be involved in the pathophysiology of acute pancreatitis. This study was designed to investigate the possible effect of pentoxifylline and alpha lipoic acid respectively and in combination on rats with L-arginine induced acute pancreatitis. Rats were divided as follow; Group 1: served as control, Group 2 and Group 3: sacrificed after 24h and 7 days; respectively, from induction of acute pancreatitis by L-arginine 250 mg/100g, Group 4 and Group 5: rats treated by pentoxifylline (12 mg/kg) and sacrificed after 24h and 7 days; respectively, from induction of acute pancreatitis, Group 6 and Group 7: treated by alpha lipoic acid (1mg/kg) and sacrificed after 24h and 7 days; respectively, from induction of acute pancreatitis, Group 8 and Group 9: treated by pentoxifylline and alpha lipoic acid and sacrificed after 24h and 7 days; respectively, from induction of acute pancreatitis. Serum samples were collected to assay levels of amylase enzyme, C-reactive protein, IL-6, catalase enzyme activity, malondialdehyde and pancreases were excised for histopathological examination and assay of pancreatic myeloperoxidase. L-arginine induced-acute pancreatitis was evident by increased in serum marker enzymes and by histopathological findings compared to control group. Pentoxifylline and alpha lipoic acid respectively provided protection against L-arginine induced acute pancreatitis possibly by their antioxidant and anti-inflammatory effect. Treatment with alpha lipoic acid exhibited pronounced improvement in the course of pancreatitis when compared to treatment with pentoxifylline. Moreover, the combination of pentoxifylline and alpha lipoic acid offered the most evident protection when compared to groups that received monotherapy; pointing to the effectiveness of such combination therapy.

Melatonin ameliorates cerulein-induced pancreatitis by the modulation of nuclear erythroid 2-related factor 2 and nuclear factor-kappaB in rats

Melatonin exhibits a wide variety of biological effects, including antioxidant and anti-inflammatory functions. Its antioxidant role impedes the etiopathogenesis of pancreatitis, but little is known about the signaling pathway of melatonin in the induction of antioxidant enzymes in acute pancreatitis (AP). The aim of this study was to determine whether melatonin could prevent cerulein-induced AP through nuclear factor erythroid 2-related factor 2 (Nrf2) and curtail inflammation by inhibition of NF-kappaB. AP was induced by two intraperitoneal (i.p.) injections of cerulein at 2 h intervals (50 microg/kg) in Sprague-Dawley rats. Melatonin (10 or 50 mg/kg/daily, i.p.) was administered 24 h before each injection of cerulein. The rats were killed 12 h after the last injection. Acinar cell degeneration, pancreatic edema, and inflammatory infiltration were significantly different in cerulein- and melatonin-treated rats. Melatonin significantly reduced amylase, lipase, MPO, and MDA levels, and increased antioxidant enzyme activities including SOD and GPx, which were decreased in AP (P < 0.05). Melatonin increased the expression of NQO1, HO-1, and SOD2 when compared with the cerulein-induced AP group (P < 0.05). In addition, melatonin increased Nrf2 expression, and reduced expressions of tumor necrosis factor-alpha, IL-1beta, IL-6, IL-8, and iNOS. The elevated nuclear binding of NF-kappaB in the cerulein-induced pancreatitis group was inhibited by melatonin. These results show that melatonin increases antioxidant enzymes and Nrf2 expression, and limits inflammatory mediators in cerulein-induced AP. It is proposed that melatonin may play an important role in oxidative stress via the Nrf2 pathway in parallel with reduction of inflammation by NF-kappaB inhibition.

Melatonin modulates the severity of taurocholate-induced acute pancreatitis in the rat

The aim of this study was to investigate the effects of melatonin on serum amylase, tumor necrosis factor-alpha (TNF-alpha) and histological changes in rats with taurocholate-induced acute pancreatitis. Thirty male Wistar rats were randomly divided into three groups; group 1, group 2 and group 3 were enrolled as melatonin, control and sham groups, respectively (n = 10 per group). Acute pancreatitis was induced by 1 ml/kg body weight using 5% taurocholate injection into the biliopancreatic duct in groups 1 and 2 after clamping the hepatic duct. Those in group 1 received 50 mg/kg body weight melatonin by intraperitoneal (i.p.) injection. Group 2 received physiological saline i.p. at the same dose. Group 3 solely underwent laparotomy with cannulation of the biliopancreatic duct. Twenty-four hours after the intervention, the rats were killed, and serum samples were collected to measure amylase and TNF-alpha levels. Simultaneously, pancreatic tissues were removed, stained with hematoxylin-eosin and examined under a light microscope. Serum amylase and TNF-alpha levels were significantly lower in the melatonin group compared to the controls (P < 0.001). The total histological score, including edema, inflammation, perivascular infiltrate, acinar necrosis, fat necrosis and hemorrhage, was also significantly lower in the melatonin group as compared to the control (P < 0.0001). In conclusion, melatonin is potentially capable of reducing pancreatic damage by decreasing serum TNF-alpha levels in taurocholate-induced acute pancreatitis in rats. This result supports the idea that melatonin might be beneficial in ameliorating the severity of acute pancreatitis.

Melatonin modulates the severity of taurocholate-induced acute pancreatitis in the rat

The aim of this study was to investigate the effects of melatonin on serum amylase, tumor necrosis factor-alpha (TNF-alpha) and histological changes in rats with taurocholate-induced acute pancreatitis. Thirty male Wistar rats were randomly divided into three groups; group 1, group 2 and group 3 were enrolled as melatonin, control and sham groups, respectively (n = 10 per group). Acute pancreatitis was induced by 1 ml/kg body weight using 5% taurocholate injection into the biliopancreatic duct in groups 1 and 2 after clamping the hepatic duct. Those in group 1 received 50 mg/kg body weight melatonin by intraperitoneal (i.p.) injection. Group 2 received physiological saline i.p. at the same dose. Group 3 solely underwent laparotomy with cannulation of the biliopancreatic duct. Twenty-four hours after the intervention, the rats were killed, and serum samples were collected to measure amylase and TNF-alpha levels. Simultaneously, pancreatic tissues were removed, stained with hematoxylin-eosin and examined under a light microscope. Serum amylase and TNF-alpha levels were significantly lower in the melatonin group compared to the controls (P < 0.001). The total histological score, including edema, inflammation, perivascular infiltrate, acinar necrosis, fat necrosis and hemorrhage, was also significantly lower in the melatonin group as compared to the control (P < 0.0001). In conclusion, melatonin is potentially capable of reducing pancreatic damage by decreasing serum TNF-alpha levels in taurocholate-induced acute pancreatitis in rats. This result supports the idea that melatonin might be beneficial in ameliorating the severity of acute pancreatitis.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.

Pathogenesis and treatment of acute pancreatitis with liver injury

Acute pancreatitis is a frequent acute abdomen in clinic, causes damages not only to pancreas, but also to distant organs. Liver is one of the mainly involved organs. The development of liver injury may aggravate pancreatitis. The pathogenesis of acute pancreatitis with liver injury is mainly related to cytokines, pancreatic enzyme, oxidative stress, microcirculation disturbance, apoptosis and pancreatitis-associated ascitic fluid, etc. Its treatment is also to eradicate these factors. However, more methods are still under animal studies. Their clinical application requires further study.

Zerumbone exerts a beneficial effect on inflammatory parameters of cholecystokinin octapeptide-induced experimental pancreatitis but fails to improve histology

OBJECTIVE

Our experiments were designed to investigate the effects of zerumbone pretreatment on cholecystokinin octapeptide (CCK-8)-induced acute pancreatitis in rats.

METHODS

Male Wistar rats weighing 240 to 280 g were divided into a control group, a group treated with CCK-8, a group receiving 20 mg/kg zerumbone before CCK-8 administration, and a group treated with zerumbone only.

RESULTS

The serum amylase and lipase activities and the pancreatic weight-body weight ratio were significantly reduced by zerumbone pretreatment, but the drug failed to influence the histological parameters of pancreatitis. The anti-inflammatory effects of the drug were manifested in decreases in the cytosolic interleukin 6 and tumor necrosis factor alpha concentrations and an elevation in the I-kappaB concentration, whereas the antioxidant ability of zerumbone was demonstrated by reductions in inducible nitric oxide synthase, Mn- and Cu/Zn-superoxide dismutase activities in the zerumbone-treated rats.

CONCLUSION

Zerumbone ameliorated the changes of several parameters of acute pancreatitis probably by interfering with I-kappaB degradation, but in the applied dose, it failed to influence the histology of the disease.

Acute pancreatitis: animal models and recent advances in basic research

Acute pancreatitis (AP) is characterized by edema, acinar cell necrosis, hemorrhage, and severe inflammation of the pancreas. Patients with AP present with elevated blood and urine levels of pancreatic digestive enzymes, such as amylase and lipase. Severe AP may lead to systemic inflammatory response syndrome and multiorgan dysfunction syndrome, which account for the high mortality rate of AP. Although most (>80%) cases of AP are associated with gallstones and alcoholism, some are idiopathic. Although the pathogenesis of AP has not yet been elucidated, a common feature is the premature activation of trypsinogen within pancreatic tissues, which triggers autodigestion of the gland. Recent advances in basic research suggest that etiologic factors including cyclooxygenase-2, substance P, and angiotensin II may have novel roles in this disease. Basic research data obtained thus far have been based on animal models of AP ranging from mild edematous pancreatitis to severe necrotizing pancreatitis. In view of this, an adequate selection of experimental animal models is of paramount importance. Notwithstanding these animal models, it should be emphasized that none of these models mimic the clinical situation where varying degrees of severity usually occur. In this review, commonly used animal models of AP will be critically evaluated. A discussion of recent advances in our knowledge about AP risk factors is also included.

Melatonin-induced gene expression changes and its preventive effects on adriamycin-induced lipid peroxidation in rat liver

Adriamycin (ADR) provokes lipid peroxidation process, while melatonin (MEL) is a free radical scavenger that has been found to protect against lipid peroxidation in vitro and in many experimental models. In the present study, the effects of ADR and the combination of ADR and MEL were analyzed on the modulation of fatty acid composition, lipid peroxidation and gene expression in rat liver. Sixty genes were selected for the study of relative gene expression changes in the liver. ADR treatment decreased the polyunsaturated fatty acids C22:6 n-3 and C20:4 n-6 in rat liver mitochondria. When the treatment of ADR was followed by MEL, decrease in these fatty acids could not be detected. A significant increase in lipid peroxidation was observed after administration of ADR, which was restored to control values by post-treatment with MEL. Gene expression profiles of ADR- versus ADR+MEL-treated rat livers indicated that both treatments induced significant changes. Quantitative real-time polymerase chain reaction analysis of 60 genes involved in oxidative stress revealed that cyp1b1, which is involved in electron transport, cyclin-dependent kinase inhibitor 1a that possesses cyclin-dependent protein kinase inhibitor activity, was induced at a more pronounced level in the ADR+MEL-treated samples than in the ADR-treated ones. Several genes having roles in heat-shock response were downregulated in MEL-treated animals, such as hsp40, hsp70 and hsp90 proteins reflecting the reduced oxidative stress in these animals. Global gene expression analysis will highlight the gene expression changes accompanying oxidative damage and its prevention in more details.