Leptin treatment ameliorates acute lung injury in rats with cerulein-induced acute pancreatitis

Acute pancreatitis: pathogenesis and emerging therapies

Acute pancreatitis is a severe inflammatory disorder with limited treatment options. Improved understanding of disease mechanisms has led to new and potential therapies. Here we summarize what we view as some of the most promising new therapies for treating acute pancreatitis, emphasizing the rationale of specific treatments based on disease mechanisms. Targeted pharmacologic interventions are highlighted. We explore potential treatment benefits and risks concerning reducing acute injury, minimizing complications, and improving long-term outcomes. Mechanisms associated with acute pancreatitis initiation, perpetuation, and reconstitution are highlighted, along with potential therapeutic targets and how these relate to new treatments.

Role of Leptin in the Digestive System

Leptin is a pluripotent peptide hormone produced mainly by adipocytes, as well as by other tissues such as the stomach. Leptin primarily acts on the central nervous system, particularly the hypothalamus, where this hormone regulates energy homeostasis and neuroendocrine function. Owing to this, disruption of leptin signaling has been linked with numerous pathological conditions. Recent studies have also highlighted the diverse roles of leptin in the digestive system including immune regulation, cell proliferation, tissue healing, and glucose metabolism. Of note, leptin acts differently under physiological and pathological conditions. Here, we review the current knowledge on the functions of leptin and its downstream signaling in the gastrointestinal tract and accessory digestive organs, with an emphasis on its physiological and pathological implications. We also discuss the current therapeutic uses of recombinant leptin, as well as its limitations.

Comparing the preventive effect of sodium hydrosulfide, leptin, and curcumin against L-arginine induced acute pancreatitis in rats: role of corticosterone and inducible nitric oxide synthase

OBJECTIVES

Acute pancreatitis (AP) is a life-threatening condition. Using antioxidants in AP is insufficient and conflicting. Therefore, this study compared the effect of hydrogen sulfide (H2S) donor, sodium hydrosulfide (NaHS), leptin or curcumin pretreatment on AP induced by L-arginine.

METHODS

Forty adult male rats were used and classified into: 1) control; 2) AP group [each rat was intraperitoneally (i.p.) injected with 2 doses of L-arginine of 250 mg/100 g body weight (b.w.) with an interval of 1 h]; 3) NaHS+AP group (each rat was i.p. injected with 10 mg/kg b.w. of NaHS 1 h before induction of AP); 4) leptin+AP group (each rat was pretreated with 10 μg/kg b.w. of leptin 30 min before induction of AP; and 5) curcumin+AP group (in which rats were i.p. injected with 150 mg/kg b.w. of curcumin 30 min before induction of AP). Serum amylase, lipase, nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and corticosterone (CORT) levels were assayed. In addition, pancreatic tissues were obtained for histopathological examination and malondialde-hyde (MDA), total antioxidant capacity (TAC), and inducible nitric oxide synthase (iNOS) levels were measured.

RESULTS

All AP treated groups showed significant decrease in serum levels of pancreatic enzymes, NO, and TNF-α, and pancreatic MDA and iNOS levels, while TAC levels were significantly increased. NaHS caused more limitation of inflammation than leptin and curcumin by affecting iNOS. Leptin was more potent than curcumin due to the stimulatory effect of leptin on glucocorticoid release to counteract inflammation.

CONCLUSIONS

NaHS was more effective in AP amelioration than the leptin and curcumin.

Leptin and Immunological Profile in Obesity and Its Associated Diseases in Dogs

Growing scientific evidence has unveiled increased incidences of obesity in domestic animals and its influence on a plethora of associated disorders. Leptin, an adipokine regulating body fat mass, represents a key molecule in obesity, able to modulate immune responses and foster chronic inflammatory response in peripheral tissues. High levels of cytokines and inflammatory markers suggest an association between inflammatory state and obesity in dogs, highlighting the parallelism with humans. Canine obesity is a relevant disease always accompanied with several health conditions such as inflammation, immune-dysregulation, insulin resistance, pancreatitis, orthopaedic disorders, cardiovascular disease, and neoplasia. However, leptin involvement in many disease processes in veterinary medicine is poorly understood. Moreover, hyperleptinemia as well as leptin resistance occur with cardiac dysfunction as a consequence of altered cardiac mitochondrial metabolism in obese dogs. Similarly, leptin dysregulation seems to be involved in the pancreatitis pathophysiology. This review aims to examine literature concerning leptin and immunological status in obese dogs, in particular for the aspects related to obesity-associated diseases.

Adipokines in critical illness: A review of the evidence and knowledge gaps

Adipose tissue products or adipokines play a major role in chronic endocrine and metabolic disorders; however, little is known about critical conditions. In this article, the experimental and clinical evidence of alterations of adipokines, adiponectin, leptin, resistin, visfatin, asymmetric dimethylarginine (ADMA), and ghrelin in critical illness, their potential metabolic, diagnostic, and prognostic value, and the gaps in the field have been reviewed. The results showed considerable changes in the concentration of the adipokines; while the impact of adipokines on metabolic disorders such as insulin resistance and inflammation has not been well documented in critically ill patients. There is no consensus about the circulatory and functional changes of leptin and adiponectin. However, it seems that lower concentrations of adiponectin at admission with gradual consequent increase might be a useful pattern in determining better outcomes of critical illness. Some evidence has suggested the adverse effects of elevated resistin concentration, potential prognostic importance of visfatin, and therapeutic value of ghrelin. High ADMA levels and low arginine:ADMA ratio were also proposed as predictors of ICU mortality and morbidities. However, there is no consensus on these findings. Although primary data indicated the role of adipokines in critical illness, further studies are required to clarify whether the reason of these changes is pathophysiological or compensatory. The relationship of pathophysiological background, disease severity, baseline nutritional status and nutrition support during hospitalization, and variations in body fat percentage and distribution with adipokines, as well as the potential prognostic or therapeutic role of these peptides should be further investigated in critically ill patients.

Intrauterine Malnutrition Reduced Long Leptin Receptor Isoform Expression and Proinflammatory Cytokine Production in Male Rat Pulmonary Endothelial Cells Stimulated by Lipopolysaccharide

Background/Aims

We have previously shown that low birth weight (LBW) rats exposed to intrauterine malnutrition have an impaired lung inflammatory response and reduced levels of inflammatory mediators; however, circulating leptin levels were not increased. We evaluated long leptin receptor isoform (ObRb) expression in lung endothelial cells from low birth weight rats and examined its role in the production of lipid mediators and cytokines.

Methods

Lung endothelial cells were obtained from normal birth weight (NBW) rats or LBW rats subjected to intrauterine malnutrition. These cells were stimulated with leptin (10 ng/mL), LPS (lipopolysaccharide, 1 μg/mL), or leptin plus LPS. Six hours after stimulation, the production of inflammatory mediators (PGE₂, LTB₄, IL-1β, and IL-6) was evaluated using commercial ELISA kits, and Western blotting was performed to investigate p38MAPK, NF-κB, and ObRb expression.

Results

Leptin increased IL-1β levels in only cells from the NBW group, whereas LPS increased PGE₂ and LTB₄ levels in cells from both groups; leptin addition potentiated lipid mediator production induced by LPS in the NBW group. LPS enhanced the production of IL-1β and IL-6 in only endothelial cells from NBW rats. Leptin receptor expression was decreased (63%) in endothelial cells from LBW rats. None of the stimuli increased NF-κB or p38 signaling pathway expression in cells from LBW rats.

Conclusion

These results suggest that intrauterine malnutrition compromises leptin receptor expression and cytokine production in pulmonary endothelial cells stimulated by LPS; these effects seem to involve the NF-κB and p38MAPK signaling pathways.

Naringenin Protects against Acute Pancreatitis in Two Experimental Models in Mice by NLRP3 and Nrf2/HO-1 Pathways

Background

Naringenin (Nar) is a type of flavonoid and has been shown to have anti-inflammatory and antioxidative properties. However, the effects of Nar on acute pancreatitis (AP) have not been well studied. In this study, we aimed to investigate the function of Nar in a mouse model of AP.

Methods

Mild acute pancreatitis (MAP) was induced by caerulein (Cae), and severe acute pancreatitis (SAP) was induced by L-arginine in mice. Nar was administered intraperitoneally at doses of 25, 50, or 100 mg/kg following MAP induction and at a dose of 100 mg/kg following SAP induction. The serum levels of cytokines, lipase, and amylase were determined, and pancreatic and pulmonary tissues were harvested.

Results

The serum levels of amylase, lipase, and cytokines were significantly decreased in both MAP and SAP models after Nar treatment. The malondialdehyde (MDA) levels of the pancreatic tissue was significantly reduced in both MAP and SAP after Nar treatment. In contrast, glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), total sulfhydryl (T-SH), and non-proteinsulthydryl (NP-SH) were markedly increased in both MAP and SAP after Nar treatment. The injury in pancreatic and pulmonary tissues was markedly improved as evidenced by the inhibited expression of myeloperoxidase, nod-like receptor protein 3, and interleukin 1 beta as well as the enhanced expression of nuclear factor erythroid 2-related factor 2/heme oxygenase-1 in pancreatic tissues.

Conclusions

Nar exerted protective effects on Cae-induced MAP and L-arginine-induced SAP in mice, suggesting that Nar may be a potential therapeutic intervention for AP.

Aspirin Protects against Acinar Cells Necrosis in Severe Acute Pancreatitis in Mice

Aspirin has a clear anti-inflammatory effect and is used as an anti-inflammatory agent for both acute and long-term inflammation. Previous study has indicated that aspirin alleviated acute pancreatitis induced by caerulein in rat. However, the role of aspirin on severe acute pancreatitis (SAP) and the necrosis of pancreatic acinar cell are not yet clear. The aim of this study was to determine the effects of aspirin treatment on a SAP model induced by caerulein combined with Lipopolysaccharide. We found that aspirin reduced serum amylase and lipase levels, decreased the MPO activity, and alleviated the histopathological manifestations of pancreas and pancreatitis-associated lung injury. Proinflammatory cytokines were decreased and the expression of NF-κB p65 in acinar cell nuclei was suppressed after aspirin treatment. Furthermore, aspirin induced the apoptosis of acinar cells by TUNEL assay, and the expression of Bax and caspase 3 was increased and the expression of Bcl-2 was decreased. Intriguingly, the downregulation of critical necrosis associated proteins RIP1, RIP3, and p-MLKL was observed; what is more, we additionally found that aspirin reduced the COX level of pancreatic tissue. In conclusion, our data showed that aspirin could protect pancreatic acinar cell against necrosis and reduce the severity of SAP. Clinically, aspirin may potentially be a therapeutic intervention for SAP.

Aspirin Protects against Acinar Cells Necrosis in Severe Acute Pancreatitis in Mice

Aspirin has a clear anti-inflammatory effect and is used as an anti-inflammatory agent for both acute and long-term inflammation. Previous study has indicated that aspirin alleviated acute pancreatitis induced by caerulein in rat. However, the role of aspirin on severe acute pancreatitis (SAP) and the necrosis of pancreatic acinar cell are not yet clear. The aim of this study was to determine the effects of aspirin treatment on a SAP model induced by caerulein combined with Lipopolysaccharide. We found that aspirin reduced serum amylase and lipase levels, decreased the MPO activity, and alleviated the histopathological manifestations of pancreas and pancreatitis-associated lung injury. Proinflammatory cytokines were decreased and the expression of NF-κB p65 in acinar cell nuclei was suppressed after aspirin treatment. Furthermore, aspirin induced the apoptosis of acinar cells by TUNEL assay, and the expression of Bax and caspase 3 was increased and the expression of Bcl-2 was decreased. Intriguingly, the downregulation of critical necrosis associated proteins RIP1, RIP3, and p-MLKL was observed; what is more, we additionally found that aspirin reduced the COX level of pancreatic tissue. In conclusion, our data showed that aspirin could protect pancreatic acinar cell against necrosis and reduce the severity of SAP. Clinically, aspirin may potentially be a therapeutic intervention for SAP.

Glycyrrhizic Acid Prevents Sepsis-Induced Acute Lung Injury and Mortality in Rats

Glycyrrhizic acid (GA), an active ingredient in licorice, has multiple pharmacological activities. However, the effects of GA on sepsis-induced acute lung injury (ALI) have not been determined. Tthe aim of this study was to investigate the molecular mechanism involved in the effects of GA against sepsis-induced ALI in rats. We found that GA alleviated sepsis-induced ALI through improvements in various pathological changes, as well as decreases in the lung wet/dry weight ratio and total protein content in bronchoalveolar lavage fluid, and a significant increase in the survival rate of treated rats. Additionally, GA markedly inhibited sepsis-induced pulmonary inflammatory responses. Moreover, we found that treatment with GA inhibited oxidative stress damage and apoptosis in lung tissue induced by ALI. Finally, GA treatment significantly inhibited NF-κ B, JNK and P38 MAPK activation. Our data indicate that GA has a protective effect against sepsis-induced ALI by inhibiting the inflammatory response, damage from oxidative stress, and apoptosis via inactivation of NF-κB and MAPK signaling pathways, providing a molecular basis for a new medical treatment for sepsis-induced ALI.

Duration of injury correlates with necrosis in caerulein-induced experimental acute pancreatitis: implications for pathophysiology

Pancreatic acinar cell necrosis is indicative of severe pancreatitis and the degree of necrosis is an index of its outcome. We studied whether the dose and duration of injury correlates with severity, particularly in terms of necrosis, in caerulein-induced acute pancreatitis (AP) in Swiss albino mice. In addition to control group 1 (G1), groups 2 and 3 received four injections of caerulein every hour but were sacrificed at five hours (G2) and nine hours (G3) respectively, and group 4 received eight injections and was sacrificed at nine hours (G4). The severity of pancreatitis was assessed histopathologically and biochemically. The histopathological scores of pancreatitis in groups 3 and 4 were significantly higher than in groups 1 and 2 (4 vs. 1, 4 vs. 2, 3 vs. 1, 3 vs. 2; P < 0.05). TUNEL-positive apoptotic cells were significantly higher in groups 2 and 3 compared with groups 1 and 4 (P < 0.05). Necrosis was significantly more in group 4 than other groups (37.49% (4.68) vs. 19.97% (1.60) in G2; 20.36% (1.56) in G3; P = 0.006 for G 2 vs. 4 and P = 0.019 for G 3 vs. 4). Electron microscopy revealed numerous autophagosomes in groups 2 and 3 and mitochondrial damage and necrosis in group 4. The pancreatic and pulmonary myeloperoxidase activity in group 4 was significantly higher than that in the other groups (P < 0.01). Hence, severity of pancreatitis is a function of the dose of injurious agent, while inflammation is both dose and duration dependent, which may also explain the wide spectrum of severity of AP seen in clinical practice.

Protective effects of alpha-lipoic Acid on oleic Acid-induced acute lung injury in rats

BACKGROUND

Oxidative stress is believed to be an important factor in the pathogenesis of acute lung injury (ALI).

AIMS

The aim of this study was to investigate the possible protective role of alpha-lipoic acid (α-LA) on oleic acid (OA)-induced ALI in rats.

STUDY DESIGN

Animal experiment.

METHODS

A total of thirty-five rats were divided into five groups in the study. Group 1 served as a control group. Rats in Group 2 (α-LA) were administered α-LA intraperitoneally at a dose of 100 mg/kg body weight (BW). Rats in Group 3 (OA) were administered OA intravenously at a dose of 100 mg/kg BW. In Group 4 (pre-OA-α-LA), α-LA was given 15 minutes prior to OA infusion, and in Group 5 (post-OA-α-LA), α-LA was given two hours after OA infusion. Four hours after the OA infusion, rats were decapitated. Blood samples were collected to measure serum levels of malondialdehyde (MDA) and glutathione (GSH), and the levels of activity for superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). Lung tissue samples were taken for histopathological examination.

RESULTS

Exposure to OA resulted in increases in serum MDA levels (p<0.001), as well as histopathological lesions in lung tissue, and decreases in CAT (p<0.05), GSH-Px (p<0.05) activities and GSH (p<0.05) levels. On the other hand, MDA levels were decreased significantly (p<0.001), while CAT (p<0.05), GSH-Px (p<0.01) activities and GSH (p<0.05) levels were increased significantly in the pre-OA-α-LA group compared with the OA group.

CONCLUSION

α-LA was found to lessen oxidative stress and to have positive effects on antioxidants in cases of OA-induced ALI. In conclusion, α-LA appears to have protective effects against ALI and potential for the prevention of ALI.

Adipokine levels in the course of mild biliary pancreatitis

OBJECTIVES

Obesity markedly increases the risk of severe acute pancreatitis (AP). Several adipokines have been ascribed a role as a predictor of clinical severity in AP. Therefore, the aim of this study was to investigate a possible relationship between leptin and adiponectin and mild biliary AP.

METHODS

We included 24 consecutive patients with mild biliary AP and 24 consecutive healthy age- and sex-matched controls. Clinical severity was classified by the Ranson score. ELISA was used to assess leptin and adiponectin levels on admission and in remission. Complete blood cell counts and other laboratory tests were also performed at baseline and in remission.

RESULTS

Leptin, adiponectin, insulin and HOMA-IR measurements showed no difference in pancreatitis patients both on admission and in remission compared to the control group. No difference was found in leptin, insulin or HOMA-IR levels in the course of pancreatitis. However, adiponectin levels were higher in remission compared to admission.

CONCLUSIONS

Increased adiponectin levels in remission may be an indication of improvement in this condition. Further studies are needed to determine whether adiponectin provides protection from AP.

Continuous regional arterial infusion with fluorouracil and octreotide attenuates severe acute pancreatitis in a canine model

Aim

To investigate the therapeutic effects of fluorouracil (5-Fu) and octreotide (Oct) continuous regional arterial infusion (CRAI,) alone or in combination, was administered in a canine model of severe acute pancreatitis (SAP).

Materials and Methods

The animals were divided into five groups; group A (Sham), group B (SAP), group C (SAP and 5-Fu), group D (SAP and Oct), and group E (SAP and 5-Fu + Oct). Levels of amylase, α-tumor necrosis factor (TNF-α), blood urea nitrogen (BUN), creatinine, thromboxane B2 and 6-keto- prostaglandin F1α were measured both before and after the induction of SAP. Pathologic examination of the pancreas and kidneys was performed after termination of the study.

Results

Pathologic changes noted in the pancreas in SAP significantly improved following CRAI with either single or combined administration of 5-Fu and Oct, where combination therapy demonstrated the lowest injury score. All treatment groups had significantly lower levels of serum TNF-α and amylase activity (P<0.05), though only groups D and E had a lower BUN level as compared to group B. The plasma thromboxane B₂ level increased in SAP, but the ratio of thromboxane B₂/6-keto- prostaglandin F_1α decreased in the treatment groups, with the combination therapy (group E) demonstrating the lowest ratio as compared to the other 3 experimental groups (P<0.05).

Conclusions

The findings in the present study demonstrate an attenuation of SAP in a canine model following CRAI administration with 5-Fu or Oct, alone or in combination.

Comparison of particle-exposure triggered pulmonary and systemic inflammation in mice fed with three different diets

BACKGROUND

Obesity can be linked to disease risks such as diabetes and cardiovascular disorders, but recently, the adipose tissue (AT) macrophage also emerges as actively participating in inflammation and immune function, producing pro- and anti-inflammatory factors. Connections between the AT and chronic lung diseases, like emphysema and asthma and a protective role of adipocyte-derived proteins against acute lung injury were suggested.In this study we addressed the question, whether a diet challenge increases the inflammatory response in the alveolar and the blood compartment in response to carbon nanoparticles (CNP), as a surrogate for ambient/urban particulate air pollutants.

METHODS

Mice were fed a high caloric carbohydrate-rich (CA) or a fat-rich (HF) diet for six weeks and were compared to mice kept on a purified low fat (LF) diet, respectively. Bronchoalveolar lavage (BAL) and blood samples were taken 24 h after intratracheal CNP instillation and checked for cellular and molecular markers of inflammation.

RESULTS AND DISCUSSION

The high caloric diets resulted in distinct effects when compared with LF mice, respectively: CA resulted in increased body and fat mass without affecting blood cellular immunity. Conversely, HF activated the blood system, increasing lymphocyte and neutrophil counts, and resulted in slightly increased body fat content. In contrast to higher pro-inflammatory BAL Leptin in CA and HF mice, on a cellular level, both diets did not lead to an increased pro-inflammatory basal status in the alveolar compartment per se, nor did result in differences in the particle-triggered response. However both diets resulted in a disturbance of the alveolar capillary barrier as indicated by enhanced BAL protein and lactate-dehydrogenase concentrations. Systemically, reduced serum Adiponectin in HF mice might be related to the observed white blood cell increase.

CONCLUSION

The increase in BAL pro-inflammatory factors in high caloric groups and reductions in serum concentrations of anti-inflammatory factors in HF mice, clearly show diet-specific effects, pointing towards augmented systemic inflammatory conditions. Our data suggest that extended feeding periods, leading to manifest obesity, are necessary to generate an increased susceptibility to particle-induced lung inflammation; although the diet-challenge already was efficient in driving pro-inflammatory systemic events.

Akt pathway is required for oestrogen-mediated attenuation of lung injury in a rodent model of cerulein-induced acute pancreatitis

BACKGROUND

The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) is known to be an endogenous negative feedback or compensatory mechanism that serves to limit pro-inflammatory and chemotactic events in response to injury. The aim of this study is to elucidate whether Akt plays any role in 17β-estradiol (E2)-mediated attenuation of lung injury after acute pancreatitis (AP).

MATERIALS AND METHODS

Male Sprague-Dawley rats underwent cerulein-induced AP. Rats were treated with vehicle (cyclodextrin), E2 (1 mg/kg body weight [BW]), or E2 plus PI3K/Akt inhibitor Wortmannin (100 μg/kg BW) 1h after the onset of AP. At 8 h after sham operation or AP, various parameters were measured.

RESULTS

AP led to a significant decrease in lung Akt phosphorylation, which was associated with increased lung tissue myeloperoxidase (MPO) activity, wet-to-dry weight ratios, interleukin (IL)-6, tumor necrosis factor (TNF)-α, cytokine-induced neutrophil chemoattractant (CINC)-1, and CINC-3 levels. Administration of E2 after AP restored the AP-induced decrease in Akt phosphorylation and attenuated the increase in lung injury markers (MPO activity and wet-to dry weight ratios) and pro-inflammatory mediator production. The effects of E2 on the lung were abolished by co-administration of Wortmannin.

CONCLUSIONS

These results collectively suggest evidences that the Akt pathway seems to be required for E2-mediated protection of lung injury after AP.

The protective effects of Lipoxin A4 during the early phase of severe acute pancreatitis in rats

OBJECTIVE

Our aim was to investigate the protective effects of a Lipoxin A(4) analogue (LXA4) in the early phase of acute pancreatitis in rats.

MATERIALS AND METHODS

Severe acute pancreatitis (SAP) was induced by injection of 5% sodium taurocholate into the pancreatic duct. Rats with SAP were treated with LXA4 (0.1 mg/kg), 10 min after the 5% sodium taurocholate injection, after which LXA4 was administrated every 8 hours, three times (LXA4 group). The sham group was only given the vehicle after operation. Plasma amylase activity, serum levels of interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α) were measured at 4, 12, and 24 h after induction of SAP. The pancreatic index and histopathologic observations were evaluated and the expression of intercellular adhesion molecule-1 (ICAM-1) and NF-κB p65 in the pancreas, and the expression of ICAM-1 in the lungs were detected by immunohistochemistry.

RESULTS

LXA4 treated rats had lower serum levels of TNF-α, IL-1, and IL-6 at all time points measured (p < 0.05), but significantly differed in plasma amylase activity only at 24 h as compared with the SAP group. The pancreatic index and the scores of pancreatitic histopathologic evaluations were lower in the LXA4 group as compared to the SAP group. Immunohistochemistry showed that LXA4 attenuated the expression of ICAM-1 and NF-κB p65 in the pancreas, as well as the expression of ICAM-1 in the lungs in animals with pancreatitis (p < 0.05).

CONCLUSIONS

We demonstrate that LXA4 has protective effects in experimental SAP, which may be achieved by inhibiting the NF-κB signalling pathway, thereby reducing the production of proinflammatory cytokines.

Endogenous leptin fluctuates in hepatic ischemia/reperfusion injury and represents a potential therapeutic target

AIM: To evaluate the role of leptin in the internal disorders during hepatic ischemia/reperfusion injury.

METHODS: A rat model of 70% hepatic ischemia/reperfusion injury was established, with groups of sham-operation (Sham), 60 min ischemia/60 min reperfusion (I60’R60’), I60’R150’, I60’R240’ and I60’R360’. Serum leptin was detected by a self-produced radioimmunoassay; serum glucose, total anti-oxidation capacity, myeloperoxidase, alanine transaminase and diamine oxidase were determined by relevant kits, while histological alterations and protein levels of leptin in the lung, liver and duodenum were examined by hematoxylin-eosin staining and immunohistochemistry. Spearman’s rank correlation between leptin and other variables or grading of tissue impairment were analyzed simultaneously.

RESULTS: Serum leptin in I60’R360’ was significantly higher than in Sham and I60’R240’ groups (both P < 0.05), serum glucose in I60’R360’ was higher than in Sham and I60’R150’ (both P < 0.05), and serum total anti-oxidation capacity in I60’R240’ and I60’R360’ were higher than in Sham (both P < 0.05) and I60’R150’groups (both P < 0.01). Serum myeloperoxidase in groups of I60’R240’ and I60’R360’ were lower than in I60’R150’group (both P < 0.05), serum alanine transaminase in the four reperfusion groups were higher than in the Sham group (all P < 0.05), while serum DAO in I60’R360’ was lower than in I60’R60’ (P < 0.05). Histological impairment in the lung, liver and duodenum at the early phase of this injury was more serious, but the impairment at the later phase was lessened gradually. Protein levels of leptin in the lung in the four reperfusion groups were significantly lower than in the Sham group (all P < 0.01), decreasing in the order of I60’R150’, I60’R60’, I60’R360’ and I60’R240’; the levels in the liver in I60’R60’ and I60’R240’ were higher than in the Sham group (both P < 0.01), while the levels in I60’R240’ and I60’R360’ were lower than in I60’R60’ (both P < 0.01); the levels in duodenum in I60’R240’ and I60’R360’ were higher than in Sham, I60’R60’ and I60’R150’ (all P < 0.01), while the level in I60’R150’ was lower than in I60’R60’ (P < 0.05). There was a significantly positive correlation between serum leptin and alanine transaminase (ρ = 0.344, P = 0.021), a significantly negative correlation between the protein level of leptin in the lung and its damage scores (ρ = -0.313, P = 0.036), and a significantly positive correlation between the protein level of leptin in the liver and its damage scores (ρ = 0.297, P = 0.047).

CONCLUSION: Endogenous leptin fluctuates in hepatic ischemia/reperfusion injury, exerts a potency to rehabilitate the internal disorders and represents a potential target for supportive therapy.

The role of leptin in the respiratory system: an overview

Since its cloning in 1994, leptin has emerged in the literature as a pleiotropic hormone whose actions extend from immune system homeostasis to reproduction and angiogenesis. Recent investigations have identified the lung as a leptin responsive and producing organ, while extensive research has been published concerning the role of leptin in the respiratory system. Animal studies have provided evidence indicating that leptin is a stimulant of ventilation, whereas researchers have proposed an important role for leptin in lung maturation and development. Studies further suggest a significant impact of leptin on specific respiratory diseases, including obstructive sleep apnoea-hypopnoea syndrome, asthma, COPD and lung cancer. However, as new investigations are under way, the picture is becoming more complex. The scope of this review is to decode the existing data concerning the actions of leptin in the lung and provide a detailed description of leptin's involvement in the most common disorders of the respiratory system.

Montelukast, a selective cysteinyl leukotriene receptor 1 antagonist, reduces cerulein-induced pancreatic injury in rats

OBJECTIVES

This study was designed to evaluate the protective effect of the cysteinyl leukotriene receptor antagonist montelukast against pancreatic injury during acute pancreatitis.

METHODS

Acute pancreatitis was induced in rats by 20-μg/kg (intraperitoneal) cerulein given at 1-hour intervals within 4 hours. Montelukast was administered intraperitoneally at a dose of 10 mg/kg 15 minutes before the first cerulein injection. Six hours after the cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and the proinflammatory cytokines tumor necrosis factor α and interleukin 1β. Pancreas tissues were taken for the determination of tissue glutathione and malondialdehyde levels and Na,K-adenosine triphosphatase and myeloperoxidase activities. The extent of tissue injury was analyzed microscopically.

RESULTS

Acute pancreatitis caused significant decreases in tissue glutathione level and Na,K-adenosine triphosphatase activity, which were accompanied with significant increases in the pancreatic malondialdehyde level, myeloperoxidase activity, and plasma cytokine level. On the other hand, montelukast treatment reversed all these biochemical indices and histopathological alterations that were induced by cerulein.

CONCLUSIONS

These results suggest that cysteinyl leukotrienes may be involved in the pathogenesis of acute pancreatitis and that the cysteinyl leukotriene receptor antagonist, montelukast, might be of therapeutic value for treatment of acute pancreatitis.

Experimental evidence of obesity as a risk factor for severe acute pancreatitis

The incidence of acute pancreatitis, an inflammation of the pancreas, is increasing worldwide. Pancreatic injury is mild in 80%-90% of patients who recover without complications. The remaining patients may develop a severe disease with local complications such as acinar cell necrosis, abscess and remote organ injury including lung injury. The early prediction of the severity of the disease is an important goal for physicians in management of patients with acute pancreatitis in order to optimize the therapy and to prevent organ dysfunction and local complications. For that purpose, multiple clinical scale scores have been applied to patients with acute pancreatitis. Recently, a new problem has emerged: the increased severity of the disease in obese patients. However, the mechanisms by which obesity increases the severity of acute pancreatitis are unclear. Several hypotheses have been suggested: (1) obese patients have an increased inflammation within the pancreas; (2) obese patients have an increased accumulation of fat within and around the pancreas where necrosis is often located; (3) increase in both peri- and intra-pancreatic fat and inflammatory cells explain the high incidence of pancreatic inflammation and necrosis in obese patients; (4) hepatic dysfunction associated with obesity might enhance the systemic inflammatory response by altering the detoxification of inflammatory mediators; and (5) ventilation/perfusion mismatch leading to hypoxia associated with a low pancreatic flow might reduce the pancreatic oxygenation and further enhance pancreatic injury. Recent experimental investigations also show an increased mortality and morbidity in obese rodents with acute pancreatitis and the implication of the adipokines leptin and adiponectin. Such models are important to investigate whether the inflammatory response of the disease is enhanced by obesity. It is exciting to speculate that manipulation of the adipokine milieu has the potential to influence the severity of acute pancreatitis.

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.

Dynamic Changes of Soluble Fas and IL-2/IL-10 in serum and Fas Expression in Lung in the Rats of Acute Necrotizing Pancreatitis

BACKGROUND

To investigate the dynamic changes of serum IL-2, IL-10, sFas and IL-2/IL-10 in a rat model with acute necrotizing pancreatitis (ANP). To explore the role of Th1/Th2 polarization and the Fas expression in the lung of rats with ANP.

METHODS

A total of 64 Sprague-Dawley rats were randomly divided into normal control group and ANP model group. ANP models were induced by injection of 50 g/L sodium taurocholate (4 mL/kg) under the pancreatic membrane. In the normal control group, the rats received isovolumetric injection of 9 g/L normal saline solution. The blood samples in each group were obtained via superior mesenteric vein for measuring IL-2, IL-10 and soluble Fas. The levels of IL-2, IL-10 and soluble Fas were determined by ELISA. The severity of lung injury was evaluated by pathologic score. The expression of Fas in lung was measured by immunohistochemistry.

RESULTS

In the ANP model group, levels of serum IL-2 were significantly higher than those of control group (P < 0.01), and peaked at 6 hours; levels of serum IL-10 were significantly higher than those of control group at 6 and 12 hours (P < 0.01); the ratios of IL-2/IL-10 were significantly higher than those of control group at 0.5 hours and 2 hours, however, they were significantly lower than those of control group at 6 hours, (P < 0.01), and returned to the normal level (P > 0.05). In Fas/APO-1 assay, there was no significant difference between the two groups. The pathological changes were aggravated significantly in model group compared with the control group. Immunohistochemistry stain showed Fas expression was absent in normal pulmonary tissue, whereas in pulmonary tissue Fas expression gradually increased 0.5 hours after induction of pancreatitis, and reached their peaks at 12 hours.

CONCLUSIONS

Fas are involved in the pathogenesis of pancreatitis associated lung injury, the mechanism might be related to the Fas mediated T helper cell apoptosis.

A murine model of obesity implicates the adipokine milieu in the pathogenesis of severe acute pancreatitis

Obesity is clearly an independent risk factor for increased severity of acute pancreatitis (AP), although the mechanisms underlying this association are unknown. Adipokines (including leptin and adiponectin) are pleiotropic molecules produced by adipocytes that are important regulators of the inflammatory response. We hypothesized that the altered adipokine milieu observed in obesity contributes to the increased severity of pancreatitis. Lean (C57BL/6J), obese leptin-deficient (LepOb), and obese hyperleptinemic (LepDb) mice were subjected to AP by six hourly intraperitoneal injections of cerulein (50 microg/kg). Severity of AP was assessed by histology and by measuring pancreatic concentration of the proinflammatory cytokines IL-1beta and IL-6, the chemokine MCP-1, and the marker of neutrophil activation MPO. Both congenitally obese strains of mice developed significantly more severe AP than wild-type lean animals. Severity of AP was not solely related to adipose tissue volume: LepOb mice were heaviest; however, LepDb mice developed the most severe AP both histologically and biochemically. Circulating adiponectin concentrations inversely mirrored the severity of pancreatitis. These data demonstrate that congenitally obese mice develop more severe AP than lean animals when challenged by cerulein hyperstimulation and suggest that alteration of the adipokine milieu exacerbates the severity of AP in obesity.

Interleukin-18, together with interleukin-12, induces severe acute pancreatitis in obese but not in nonobese leptin-deficient mice

Obesity is associated with increased severity of acute pancreatitis (AP). The cytokines IL-18 and IL-12 are elevated in patients with AP, and IL-18 levels are high in obesity. We aimed to develop a pathologically relevant model to study obesity-associated severe AP. Lean WT and obese leptin-deficient ob/ob mice received two injections of IL-12 plus IL-18. Survival, pancreatic inflammation, and biochemical markers of AP were measured. Dosing with IL-12 plus IL-18 induced 100% lethality in ob/ob mice; no lethality was observed in WT mice. Disruption of pancreatic exocrine tissue and acinar cell death as well as serum amylase and lipase levels were significantly higher in ob/ob than in WT mice. Edematous AP developed in WT mice, whereas obese ob/ob mice developed necrotizing AP. Adipose tissue necrosis and saponification were present in cytokine-injected ob/ob but not in WT mice. Severe hypocalcemia and elevated acute-phase response developed in ob/ob mice. The cytokine combination induced high levels of regenerating protein 1 and pancreatitis-associated protein expression in the pancreas of WT but not of ob/ob mice. To differentiate the contribution of obesity to that of leptin deficiency, mice received short- and long-term leptin replacement therapy. Short-term leptin reconstitution in the absence of major weight loss did not protect ob/ob mice, whereas leptin deficiency in the absence of obesity resulted in a significant reduction in the severity of the pancreatitis. In conclusion, we developed a pathologically relevant model of AP in which obesity per se is associated with increased severity.

Alveolar macrophage activation and an emphysema-like phenotype in adiponectin-deficient mice

Adiponectin is an adipocyte-derived collectin that acts on a wide range of tissues including liver, brain, heart, and vascular endothelium. To date, little is known about the actions of adiponectin in the lung. Herein, we demonstrate that adiponectin is present in lung lining fluid and that adiponectin deficiency leads to increases in proinflammatory mediators and an emphysema-like phenotype in the mouse lung. Alveolar macrophages from adiponectin-deficient mice spontaneously display increased production of tumor necrosis factor-alpha (TNF-alpha) and matrix metalloproteinase (MMP-12) activity. Consistent with these observations, we found that pretreatment of alveolar macrophages with adiponectin leads to TNF-alpha and MMP-12 suppression. Together, our findings show that adiponectin leads to macrophage suppression in the lung and suggest that adiponectin-deficient states may contribute to the pathogenesis of inflammatory lung conditions such as emphysema.

The inflammatory cascade in acute pancreatitis: relevance to clinical disease

Acute pancreatitis is an inflammatory condition that is initiated by the intra pancreatic activation of proteases. Pancreatic enzyme activation triggers a local and systemic inflammatory response that is associated with recruitment of inflammatory cells into the pancreas and a widespread up-regulation of inflammatory markers in distant tissues.