L-Arginine-induced acute pancreatitis results in mild lung inflammation without altered respiratory mechanics

A Severe Acute Pancreatitis Mouse Model Transited from Mild Symptoms Induced by a “Two-Hit” Strategy with L-Arginine

To develop a severe acute pancreatitis (SAP) model transited from mild symptoms, we investigated a “two-hit” strategy with L-arginine in mice. The mice were intraperitoneally injected with ice-cold L-arginine (4 g/kg) twice at an interval of 1 h on the first day and subjected to the repeated operation 72 h afterwards. The results showed the “two-hit” strategy resulted in the destructive damage and extensive necrosis of acinar cells in the pancreas compared with the “one-hit” model. Meanwhile, excessive levels of pro-inflammatory mediators, namely IL-6 and TNF-α, were released in the serum. Remarkably, additional deleterious effects on multiple organs were observed, including high intestinal permeability, kidney injury, and severe acute lung injury. Therefore, we confirmed that the SAP animal model triggered by a “two-hit” strategy with L-arginine was successfully established, providing a solid foundation for a deeper understanding of SAP initiation and therapy research to prevent worsening of the disease.

Prevention and Amelioration of Rodent Ventilation-Induced Lung Injury with Either Prophylactic or Therapeutic feG Administration

PURPOSE

Mechanical ventilation is a well-established therapy for patients with acute respiratory failure. However, up to 35% of mortality in acute respiratory distress syndrome may be attributed to ventilation-induced lung injury (VILI). We previously demonstrated the efficacy of the synthetic tripeptide feG for preventing and ameliorating acute pancreatitis-associated lung injury. However, as the mechanisms of induction of injury during mechanical ventilation may differ, we aimed to investigate the effect of feG in a rodent model of VILI, with or without secondary challenge, as a preventative treatment when administered before injury (prophylactic), or as a therapeutic treatment administered following initiation of injury (therapeutic).

METHODS

Lung injury was assessed following prophylactic or therapeutic intratracheal feG administration in a rodent model of ventilation-induced lung injury, with or without secondary intratracheal lipopolysaccharide challenge.

RESULTS

Prophylactic feG administration resulted in significant improvements in arterial blood oxygenation and respiratory mechanics, and decreased lung oedema, bronchoalveolar lavage protein concentration, histological tissue injury scores, blood vessel activation, bronchoalveolar lavage cell infiltration and lung myeloperoxidase activity in VILI, both with and without lipopolysaccharide. Therapeutic feG administration similarly ameliorated the severity of tissue damage and encouraged the resolution of injury. feG associated decreases in endothelial adhesion molecules may indicate a mechanism for these effects.

CONCLUSIONS

This study supports the potential for feG as a pharmacological agent in the prevention or treatment of lung injury associated with mechanical ventilation.

A novel acute necrotizing pancreatitis model induced by L-arginine in rats

OBJECTIVE

This study developed a novel protocol for creating an acute necrotizing pancreatitis model in rats using L-arginine.

METHODS

Anesthetic laparotomy was performed on the upper abdomen, and the pancreatic parenchyma of Sprague-Dawley rats was injected with 1 mL of sterilized L-arginine solution at 5 different locations in the experimental group. Specifically, 2 different injection points in the head and body of the pancreas were chosen randomly, and 1 injection point in the tail of the pancreas was chosen randomly. The parenchyma of the pancreas was injected with 200 μL of an L-arginine solution at each point. The optimal dose of L-arginine per rat was 0.4 g/kg.

RESULTS

Serum amylase activity increased significantly after targeted injection into the parenchyma of the pancreas. Pathological examination of the pancreas 24 hours after L-arginine injection revealed massive interstitial edema, apoptosis, and necrosis of acinar cells with an infiltration of neutrophils, granulocytes, and monocytes.

CONCLUSIONS

The present study developed an appropriate, workable, and reproducible rat model of acute necrotizing pancreatitis with higher survivability and success rates compared with previously published methods.

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.

Tripeptide feG prevents and ameliorates acute pancreatitis-associated acute lung injury in a rodent model

BACKGROUND

The synthetic tripeptide feG (D-Phe-D-Glu-Gly) is a novel pharmacologic agent that decreases neutrophil recruitment, infiltration, and activation in various animal models of inflammatory disease. We aimed to investigate the effect of feG as both a preventive treatment when administered before acute lung injury and as a therapeutic treatment administered following initiation of acute lung injury.

METHODS

Lung injury was assessed following prophylactic or therapeutic intratracheal feG administration in a “two-hit” rodent model of acute pancreatitis plus intratracheal lipopolysaccharide.

RESULTS

Following both prophylactic and therapeutic feG administration, there were significant improvements in arterial blood oxygenation and respiratory mechanics and decreased lung edema, BAL protein concentration, histologic tissue injury scores, BAL cell infiltration, and lung myeloperoxidase activity. Most indices of lung damage were reduced to baseline control values.

CONCLUSIONS

feG reduced leukocyte infiltration, ameliorated the severity of inflammatory damage, and restored lung function when administered either prophylactically or therapeutically in a two-hit rat model of acute pancreatitis plus intratracheal lipopolysaccharide.

Nitric oxide synthase inhibition reduces albumin induced lung damage in acute pancreatitis

BACKGROUND/OBJECTIVES

Colloid resuscitation in acute pancreatitis (AP) is a matter of controversy due to the possible deleterious effect on lung function. A previous study demonstrates that albumin administration increases lung damage in burns and this effect can be reversed by inducible nitric oxide synthase (iNOS) inhibition. This study evaluates the effects of S-methylisothiourea (SMT), a specific iNOS inhibitor, on lungs and pancreas of rats with AP receiving intravenous albumin.

METHODS

AP was induced in Wistar rats by intraductal 5% taurocholate injection. To evaluate the effect of albumin on lung damage, animals received IV saline or human albumin immediately after AP (Groups: Saline and Albumin). To evaluate the effect of iNOS inhibition on lung damage, SMT was given immediately after AP (Group Saline+SMT, and Group Albumin+SMT). At 12 h after AP induction, serum amylase activity, lung vascular permeability and myeloperoxidase (MPO) activity were evaluated. Lung and pancreas histological analysis were performed.

RESULTS

Serum amylase activity, pancreatic edema, lung vascular permeability, MPO activity, and inflammatory infiltration were significantly increased after AP. Albumin administration increased lung vascular permeability, inflammatory infiltration, and pancreatic edema compared to saline administration (p < 0.05). Albumin administration with SMT reduced lung vascular permeability, MPO activity, and inflammatory infiltration compared to albumin administration alone (p < 0.05).

CONCLUSION

Lung and pancreatic damage induced by albumin administration for restoration of plasma volume in AP are reduced by iNOS inhibition. Awareness of this fact may be useful in high-risk patients who need to receive albumin for volume replacement.

Prevention and amelioration of rodent endotoxin-induced lung injury with administration of a novel therapeutic tripeptide feG

BACKGROUND

The synthetic tripeptide feG is a novel pharmacological agent that decreases neutrophil recruitment, infiltration, and activation in various animal models of inflammatory disease. In human and rat cell culture models, feG requires pre-stimulation in order to decrease in vitro neutrophil chemotaxis. We aimed to investigate the effect of feG on neutrophil chemotaxis in a lipopolysaccharide-induced acute lung injury model without pre-stimulation.

METHODS

The efficacy of feG as both a preventative treatment, when administered before lung injury (prophylactic), or as a therapeutic treatment, administered following lung injury (therapeutic), was investigated.

RESULTS

Prophylactic or therapeutic feG administration significantly reduced leukocyte infiltration, ameliorated the severity of inflammatory damage, and restored lung function. feG was demonstrated to significantly decrease bronchoalveolar lavage cell infiltration, lung myeloperoxidase activity, lung oedema, histological tissue injury scores, and improve arterial blood oxygenation and respiratory mechanics.

CONCLUSIONS

feG reduced leukocyte infiltration, ameliorated the severity of inflammatory damage, and restored lung function when administered prophylactically or therapeutically in a rodent model of lipopolysaccharide-induced acute lung injury, without the need for pre-stimulation, suggesting a direct rather than indirect mechanism of action in the lung.

Evaluation of lung injury and respiratory mechanics in a rat model of acute pancreatitis complicated with endotoxin

BACKGROUND

Acute lung injury (ALI) is a common complication of acute pancreatitis (AP) and contributes to the majority of AP-associated deaths, particularly in the setting of secondary infection. This 'two-hit' model mimics clinical cases where the presentation of AP is associated with mild lung injury that, following a secondary direct lung infection, can result in respiratory dysfunction and death. We therefore aimed to characterize lung injury in a clinically-relevant 'two-hit' rat model of caerulein-induced AP combined with intratracheal endotoxin.

METHODS

Rats received 7 hourly intraperitoneal injections of caerulein (50 μg/kg). Twenty four hours following the first caerulein injection, rats were anaesthetised and LPS (15 mg/kg) was instilled intratracheally. Following LPS instillation, rats were ventilated for a total of 2 h.

RESULTS

In the present study, AP results in mild pulmonary injury indicated by increased lung myeloperoxidase (MPO) activity and edema, but with no alteration of respiratory function, while intratracheal instillation of LPS results in more substantial pulmonary injury. The induction of AP challenged with secondary intratracheal LPS results in an exacerbation of lung damage indicated by further increased lung edema, plasma and bronchoalveolar (BAL) CINC-1 concentration, lung damage histology score, and lung tissue resistance and elastance, compared with LPS alone.

CONCLUSIONS

In conclusion, the addition of instilled LPS acted as a "second-hit" and exacerbated caerulein-induced AP, compared with the induction of AP alone or the instillation of LPS alone. Given its clinical relevance, this model could prove useful for examination of therapeutic interventions for ALI following secondary infection.

Lung injury in acute pancreatitis: mechanisms underlying augmented secondary injury

Acute lung injury (ALI) and its more severe form, the acute respiratory distress syndrome (ARDS), are common complications of acute pancreatitis (AP). ALI/ARDS contribute to the majority of AP-associated deaths, particularly in the setting of secondary infection. Following secondary pulmonary infection there can be an exacerbation of AP-associated lung injury, greater than the sum of the individual injuries alone. The precise mechanisms underlying this synergism, however, are not known. In this review we discuss the main factors contributing to the development of augmented lung injury following secondary infection during AP and review the established models of AP in regard to the development of associated ALI.