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

Uncoupling Protein 2 as a Pathogenic Determinant and Therapeutic Target in Cardiovascular and Metabolic Diseases

Uncoupling protein 2 (UCP2) is a mitochondrial protein that acts as an anion carrier. It is involved in the regulation of several processes, including mitochondrial membrane potential, generation of reactive oxygen species within the inner mitochondrial membrane and calcium homeostasis. UCP2 expression can be regulated at different levels: genetic (gene variants), transcriptional [by peroxisome proliferator-activated receptors (PPARs) and microRNAs], and post-translational. Experimental evidence indicates that activation of UCP2 expression through the AMPK/PPAR-α axis exerts a protective effect toward renal damage and stroke occurrence in an animal model of ischemic stroke (IS) associated with hypertension. UCP2 plays a key role in heart diseases (myocardial infarction and cardiac hypertrophy) and metabolic disorders (obesity and diabetes). In humans, UCP2 genetic variants (-866G/A and Ala55Val) associate with an increased risk of type 2 diabetes mellitus and IS development. Over the last few years, many agents that modulate UCP2 expression have been identified. Some of them are natural compounds of plant origin, such as Brassica oleracea, curcumin, berberine and resveratrol. Other molecules, currently used in clinical practice, include anti-diabetic (gliptin) and chemotherapeutic (doxorubicin and taxol) drugs. This evidence highlights the relevant role of UCP2 for the treatment of a wide range of diseases, which affect the national health systems of Western countries. We will review current knowledge on the physiological and pathological implications of UCP2 with particular regard to cardiovascular and metabolic disorders and will focus on the available therapeutic approaches affecting UCP2 level for the treatment of human diseases.

Cashew (Anacardium occidentale L.) Nuts Modulate the Nrf2 and NLRP3 Pathways in Pancreas and Lung after Induction of Acute Pancreatitis by Cerulein

BACKGROUND

One of the most common co-morbidities, that often leads to death, associated with acute pancreatitis (AP) is represented by acute lung injury (ALI). While many aspects of AP-induced lung inflammation have been investigated, the involvement of specific pathways, such as those centered on nuclear factor E2-related factor 2 (Nrf2) and nucleotide-binding domain leucine-rich repeat (NLR) and pyrin domain containing receptor 3 (NLRP3), has not been fully elucidated.

METHODS

To investigate the effect of cashew (Anacardium occidentale L.) nuts on pancreatic and lung injury induced by cerulein injection, cerulein (50 μg/kg) was administered to CD1 mice for 10 h. Oral treatment with cashew nuts at a dose of 100 mg/kg was given 30 min and 2 h after the first cerulein injection. One hour after the final cerulein injection, mice were euthanized and blood, lung and pancreatic tissue samples were collected.

RESULTS

Cashew nuts were able to (1) reduce histological damage; (2) mitigate the induction of mast cell degranulation as well as the activity of myeloperoxidase and malondialdehyde; (3) decrease the activity levels of amylase and lipase as well as the levels of pro-inflammatory cytokines; and (4) enhance the activation of the Nrf2 pathway and suppress the activation of the NLRP3 pathway in response to cerulein in both pancreas and lung.

CONCLUSIONS

Cashew nuts could have a beneficial effect not only on pancreatitis but also on lung injury induced by cerulein.

Myrtus communis leaf extract protects against cerulein-induced acute pancreatitis in rats

In this study, the aim was to examine the potential protective effects of Myrtus communis subsp. communis leaf ethanol extract (MC) treatment against acute pancreatitis (AP) in rats. Thirty-two rats were grouped as the saline-pretreated control (C), MC-pretreated control (MC), saline-pretreated AP (AP), and MC-pretreated AP (MC + AP) groups. To induce AP, cerulein was administered (50 µg/kg) two times. The rats were given MC for 14 days before cerulein injection. Six hours after the final cerulein injection, the rats were sacrificed. Pancreatic damage was associated with an increase in the serum activity of lipase and amylase, the pancreatic activity of myeloperoxidase, and the pancreatic level of malondialdehyde, interleukin-1β, and interleukin-6. AP also led to a decrease in the pancreatic level of anti-inflammatory interleukin-10 and glutathione. Pretreatment with MC before the induction of AP significantly reduced the pancreatic damage observed during the histological examination as well as reversed the biochemical changes evoked by AP. PRACTICAL APPLICATIONS: Acute pancreatitis is characterized by high mortality (average about 5%; severe cases may reach about 30%). The current treatment for acute pancreatitis is mainly symptomatic. The introduction of herbal drugs may lead to the development of a new strategy in the treatment of this disease. This study revealed that MC reduced pancreatic injury by decreasing pro-inflammatory cytokines, increasing antioxidant capacity and anti-inflammatory cytokine, IL-10. To the authors' knowledge, this research is the first report showing that MC inhibits the development of AP. This observation suggests that MC may be useful in the prevention and the treatment of AP in clinical settings.

Effect of Endotoxemia in Suckling Rats on Pancreatic Integrity and Exocrine Function in Adults: A Review Report

Background. Endotoxin (LPS), the component of Gram-negative bacteria, is responsible for sepsis and neonatal mortality, but low concentrations of LPS produced tissue protection in experimental studies. The effects of LPS applied to the suckling rats on the pancreas of adult animals have not been previously explored. We present the impact of neonatal endotoxemia on the pancreatic exocrine function and on the acute pancreatitis which has been investigated in the adult animals. Endotoxemia was induced in suckling rats by intraperitoneal application of LPS from Escherichia coli or Salmonella typhi. In the adult rats, pretreated in the early period of life with LPS, histological manifestations of acute pancreatitis have been reduced. Pancreatic weight and plasma lipase activity were decreased, and SOD concentration was reversed and accompanied by a significant reduction of lipid peroxidation products (MDA + 4 HNE) in the pancreatic tissue. In the pancreatic acini, the significant increases in protein signals for toll-like receptor 4 and for heat shock protein 60 were found. Signal for the CCK1 receptor was reduced and pancreatic secretory responses to caerulein were diminished, whereas basal enzyme secretion was unaffected. These pioneer studies have shown that exposition of suckling rats to endotoxin has an impact on the pancreas in the adult organism.

Protective Effects of Hydrogen Gas on Experimental Acute Pancreatitis

Acute pancreatitis (AP) is an inflammatory disease mediated by damage to acinar cells and pancreatic inflammation. In patients with AP, subsequent systemic inflammatory responses and multiple organs dysfunction commonly occur. Interactions between cytokines and oxidative stress greatly contribute to the amplification of uncontrolled inflammatory responses. Molecular hydrogen (H2) is a potent free radical scavenger that not only ameliorates oxidative stress but also lowers cytokine levels. The aim of the present study was to investigate the protective effects of H2 gas on AP both in vitro and in vivo. For the in vitro assessment, AR42J cells were treated with cerulein and then incubated in H2-rich or normal medium for 24 h, and for the in vivo experiment, AP was induced through a retrograde infusion of 5% sodium taurocholate into the pancreatobiliary duct (0.1 mL/100 g body weight). Wistar rats were treated with inhaled air or 2% H2 gas and sacrificed 12 h following the induction of pancreatitis. Specimens were collected and processed to measure the amylase and lipase activity levels; the myeloperoxidase activity and production levels; the cytokine mRNA expression levels; the 8-hydroxydeoxyguanosine, malondialdehyde, and glutathione levels; and the cell survival rate. Histological examinations and immunohistochemical analyses were then conducted. The results revealed significant reductions in inflammation and oxidative stress both in vitro and in vivo. Furthermore, the beneficial effects of H2 gas were associated with reductions in AR42J cell and pancreatic tissue damage. In conclusion, our results suggest that H2 gas is capable of ameliorating damage to the pancreas and AR42J cells and that H2 exerts protective effects both in vitro and in vivo on subjects with AP. Thus, the results obtained indicate that this gas may represent a novel therapy agent in the management of AP.

Redox signaling in acute pancreatitis

Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF-VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis.

Effectiveness of interleukin-1 receptor antagonist (Anakinra) on cerulein-induced experimental acute pancreatitis in rats

AIM

Acute pancreatitis (AP) is defined as an inflammatory disease of the pancreas. The purpose of this study was to examine the effectiveness of Anakinra on cerulein-induced experimental pancreatitis rat model by using the results of biochemical and histopathological findings.

MATERIALS AND METHODS

Cerulein was administered to induce AP in rats. Group 1 was the sham group. Subcutancerulein was injected to the rats in group 2 for experimental pancreatitis group. In groups 3 and 4, 100 and 50 mg/kg intraperitoneal Anakinra were injected after the induction of experimental pancreatitis by subcutaneous cerulein in rats, respectively. Lastly, in group 5, rats were injected with intraperitoneal saline and subcutan cerulean for placebo group. The following parameters were evaluated: histopathological score of pancreatitis, apoptotic index, amylase, lipase, TNF-α levels, IL-1β and the leukocyte count.

RESULTS

When the results of serum amylase, lipase, TNF-α and IL-1β levels, the leukocyte count, histopathologic scores and apoptotic indices of control group compared to the results of other groups, the differences exhibited statistical significance (all p < 0.05). On the other hand, when the results of fourth group compared with the results of third group, the data demonstrated statistical insignificance (p > 0.05). However, no any significant differences were found between the results of fourth and fifth groups (p > 0.05).

CONCLUSION

In the light of these results, cerulein is an appropriate agent for experimental AP rat model and Anakinra has a favorable therapeutic effect on acute experimental pancreatitis model. Moreover, Anakinra significantly decreases cerulein-related pancreatic tissue injury and pancreatic apoptosis.

From nitric oxide to hyperbaric oxygen: invisible and subtle but nonnegligible gaseous signaling molecules in acute pancreatitis

Nitric oxide (NO), carbon monoxide, and hydrogen sulfide in addition to hydrogen are well established as gaseous signal molecules throughout the body. Although the role of gasotransmitters in acute pancreatitis (AP) has been explored for many years, many details remain to be elucidated. The physiologic effect of NO in AP mainly relies on induced NO synthase, which stimulates the production of cytokines in the blood. Carbon monoxide inhibits nuclear factor-κB activation, which leads to amelioration of the inflammatory response. Hydrogen sulfide displays a dual role in the mechanism of AP according to its concentration in the system. Hydrogen is a newly discovered gaseous signaling molecule, and currently, there is little evidence that it has any function in alleviating inflammation. We discovered that hyperbaric oxygen is a novel gasotransmitter that has potential use in the treatment of AP. The correlation among hyperbaric oxygen, hypoxia inducible factor 1α, and other signaling pathways should be further studied. We also discuss some prospects and issues that remain to be resolved in this review. In summary, the discovery of gaseous signal molecules has established a new platform for deep investigation of the mechanism of AP, and our knowledge of the role of gasotransmitters in AP will increase with further research.

Guanylate cyclase inhibition by methylene blue in circulatory shock caused by acute necrotizing pancreatitis: a word of caution based on a porcine model

OBJECTIVE

To study the therapeutic application of guanylate cyclase inhibition by methylene blue in an experimental model of acute pancreatitis in pigs.

METHODS

acute necrotizing pancreatitis was induced in anesthetized pigs by the retrograde infusion of 1 ml/kg of 5% sodium taurocholate and 8 U/kg enterokinase in the pancreatic duct. Three groups were studied (n = 5): control (C), pancreatitis (AP), and MB bolus followed by pancreatitis (MB+P). The data included serum and abdominal fluid enzymes, hemodynamic variables, arterial hemogasometry, abdominal fluid volume, inflammatory markers, plasma nitrite/nitrate (NOx), plasma myeloperoxidase (MPO) and plasma malondialdehyde (MDA). One- and two-way analysis of variance (ANOVA) was performed, followed by the Bonferroni test (p < 0.05).

RESULTS

amylase and lipase were three and 10-fold higher in the AP group. Myeloperoxidase activity was 50% higher in the AP group. The hemodynamic data indicated early hypovolemic shock followed by cardiogenic shock. Severe fluid translocation to the peritoneal cavity was observed. Plasma NOx remained unchanged. The MB+P group had a five-fold increase in MDA compared with the C group.

CONCLUSION

preemptive application of MB in pigs with AP demonstrated no significant effects on hemodynamic and inflammatory variables. The use of MB is inadequate in cases of exponential NO release, and extreme caution must be exercised, given the increase in lipid peroxidation based on the malondialdehyde dosage.

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

SIGNIFICANCE

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

RECENT ADVANCES

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

CRITICAL ISSUES

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

FUTURE DIRECTIONS

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

Sesamol attenuates oxidative stress–mediated experimental acute pancreatitis in rats

Acute pancreatitis is a potentially fatal disease with no known cure. The initial events in acute pancreatitis may occur within the acinar cells. We examined the effect of sesamol on (i) a cerulein-induced pancreatic acinar cancer cell line, AR42J, and (ii) cerulein-induced experimental acute pancreatitis in rats. Sesamol inhibited amylase activity and increased cell survival. It also inhibited medium lipid peroxidation and 8-hydroxydeoxyguanosine in AR42J cells compared with the cerulein-alone groups. In addition, in cerulein-treated rats, sesamol inhibited serum amylase and lipase levels, pancreatic edema, and lipid peroxidation, but it increased pancreatic glutathione and nitric oxide levels. Thus, we hypothesize that sesamol attenuates cerulein-induced experimental acute pancreatitis by inhibiting the pancreatic acinar cell death associated with oxidative stress in rats.

Protective effects of lycopene on cerulein-induced experimental acute pancreatitis in rats

BACKGROUND

The purpose of our study was to evaluate the protective effect of the strong antioxidant and anti-inflammatory agent, lycopene, on oxidative stress in a rat model of cerulein-induced acute edematous pancreatitis.

METHODS

Sprague-Dawley rats were pretreated with lycopene (50 mg/kg, i.p.) or saline 15 min before cerulein was given 20 μg/kg (i.p.) at 1-h intervals within 4 h. Twelve hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1ß). Pancreatic tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na(+)/K(+)-ATPase, and myeloperoxidase (MPO) activities. Tissue samples were also examined histologically.

RESULTS

Acute pancreatitis caused significant decrease in tissue GSH levels and Na(+)/K(+)-ATPase activity, while pancreatic MDA levels and MPO activity were increased. Furthermore, TNF-α, IL-1ß, and amylase lipase levels were also significantly increased. On the other hand, lycopene pretreatment reserved all these biochemical indices as well as histopathologic alterations that were induced by cerulein.

CONCLUSIONS

According to the results, lycopene protects the pancreatic tissues from oxidative damage induced by cerulein, and this effect possibly involves the inhibition of neutrophil infiltration and lipid peroxidation. These results suggest that high dietary intake of tomatoes may have protective effects against acute pancreatitis.

Liver lipid peroxidation and antioxidant capacity in cerulein-induced acute pancreatitis

The aim of this study was to evaluate the role of oxidative damage in pancreatitis-induced hepatic injury. Thirty-five rats were divided into five groups (each of 7 rats): control, cerulein (100 microg/kg body weight), cerulein and pentoxifylline (12 mg/kg body weight), cerulein plus L-NAME (10 mg/kg body weight) and cerulein plus L-arginine (160 mg/kg body weight). The degree of hepatic cell degeneration differed significantly between groups. Mean malondialdehyde levels were 7.00 +/- 2.29, 20.89 +/- 10.13, 11.52 +/- 4.60, 18.69 +/- 8.56, and 8.58 +/- 3.68 nmol/mg protein for the control, cerulein, pentoxifylline, L-NAME, and L-arginine groups, respectively. Mean catalase activity was 3.20 +/- 0.83, 1.09 +/- 0.35, 2.05 +/- 0.91, 1.70 +/- 0.60, and 2.85 +/- 0.47 U/mg protein for the control, cerulein, pentoxifylline, L-NAME, and L-arginine groups, respectively, and mean glutathione peroxidase activity was 0.72 +/- 0.25, 0.33 +/- 0.09, 0.37 +/- 0.04, 0.34 +/- 0.07 and 0.42 +/- 0.1 U/mg protein for the control, cerulein, pentoxifylline, L-NAME, and L-arginine groups, respectively. Cerulein-induced liver damage was accompanied by a significant increase in tissue malondialdehyde levels (P < 0.05) and a significant decrease in catalase (P < 0.05) and GPx activities (P < 0.05). L-arginine and pentoxifylline, but not L-NAME, protected against this damage. Oxidative injury plays an important role not only in the pathogenesis of AP but also in pancreatitis-induced hepatic damage.

Protective Effects of Proanthocyanidin on Cerulein-induced Acute Pancreatic Inflammation in Rats

Background

The aim of this study was to assess the possible protective effect of proanthocyanidin against cerulein-induced acute pancreatic inflammation (AP) and oxidative injury.

Methods

Sprague-Dawley rats were pretreated with proanthocyanidine (100 mg/kg, orally) or saline 15 min before cerulein was given by 20 µg/kg subcutaneously at 1-h intervals within 4 hours. Six hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1b). Pancreas tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na⁺, K⁺-ATPase and myeloperoxidase (MPO) activities. Formation of reactive oxygen species in pancreatic tissue samples was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes, while the extent of tissue injury was analyzed microscopically.

Results

Acute pancreatitis caused a significant decrease in tissue GSH level and Na⁺, K⁺-ATPase activity, which was accompanied with significant increases in the pancreatic MDA, luminol and lucigenin chemiluminescences (CL) levels and MPO activity. Similarly TNF-α and IL-1β levels were elevated in the pancreatic group as compared to control group. On the other hand, proanthocyanidin treatment reversed all these biochemical indices, as well as histopathological alterations that were induced by cerulein.

Conclusions

Proanthocyanidine can ameliorate pancreatic injury induced by cerulein in rats, this result suggests that proanthocyanidin may have utility in treating acute pancreatititis.