雨蛙素联合脂多糖致小鼠重症急性胰腺炎模型的建立及其机理的探讨

为建立一种快速、简便、无创伤性的小鼠重症急性胰腺炎模型。本实验运用雨蛙素联合脂多糖小鼠腹腔内给药;血淀粉酶和胰腺湿重测定;胰腺和胰外器官病理学检查;腺泡细胞透射电镜观察;血清NO浓度测定;胰腺组织SOD和MDA测定。结果发现,雨蛙素联合脂多糖组血淀粉酶、NO浓度和胰腺湿重均增高,SOD活力降低,MDA含量升高,胰腺间质水肿、实质出血坏死、炎症细胞浸润,腺泡细胞受损严重,胰外多器官受到不同程度的损害;雨蛙素组胰腺无明显出血坏死,胰外器官正常;脂多糖组胰腺基本正常,胰外器官轻微炎症浸润。由本实验结果显示,雨蛙素联合脂多糖致小鼠重症急性胰腺炎模型具有人类重症急性胰腺炎的病理特征,为非创伤性,成模快速稳定,重复性好;脂多糖促使雨蛙素诱导的急性水肿型胰腺炎重症化的机理与自由基释放-清除机制和氧化-抗氧化机制紊乱有关。     

The tripeptide analog feG ameliorates severity of acute pancreatitis in a caerulein mouse model

Acute pancreatitis (AP) is associated with significant morbidity and mortality; however, there is no specific treatment for this disease. A novel salivary tripeptide analog, feG, reduces inflammation in several different animal models of inflammation. The aims of this study were to determine whether feG reduced the severity of AP and modifies the expression of pancreatic ICAM-1 mRNA during AP in a mouse model. AP was induced in mice by hourly (x12) intraperitoneal injections of caerulein. A single dose of feG (100 microg/kg) was coadministered with caerulein either at time 0 h (prophylactic) or 3 h after AP induction (therapeutic). Plasma amylase and pancreatic MPO activities and pancreatic ICAM-1 mRNA expression (by RT-PCR) were measured. Pancreatic sections were histologically assessed for abnormal acinar cells and interstitial space. AP induction produced a sevenfold increase in plasma amylase, a tenfold increase in pancreatic MPO activity, and a threefold increase in interstitial space, and 90% of the acinar cells were abnormal. Prophylactic treatment with feG reduced the AP-induced plasma amylase activity by 45%, pancreatic MPO by 80%, the proportion of abnormal acinar cells by 30%, and interstitial space by 40%. Therapeutic treatment with feG significantly reduced the AP-induced abnormal acinar cells by 10% and the interstitial space by 20%. Pancreatic ICAM-1 mRNA expression was upregulated in AP and was reduced by 50% with prophylactic and therapeutic treatment with feG. We conclude that feG ameliorates experimental AP acting at least in part by modulating ICAM-1 expression in the pancreas.     

Development of a new mouse model of acute pancreatitis induced by administration of L-arginine

The pathogenesis of acute pancreatitis is not fully understood. Experimental animal models that mimic human disease are essential to better understand the pathophysiology of the disease and to evaluate potential therapeutic agents. Given that the mouse genome is known completely and that a large number of strains with various genetic deletions are available, it is advantageous to have multiple reliable mouse models of acute pancreatitis. Presently, there is only one predominant model of acute pancreatitis in mice, in which hyperstimulatory doses of cholecystokinin or its analog caerulein are administered. Therefore, the aim of this study was to develop another mouse model of acute pancreatitis. In this study, C57BL/6 mice were injected intraperitoneally with L-arginine in two doses of 4 g/kg each, 1 h apart. Serum amylase, myeloperoxidase, and histopathology were examined at varying time points after injection to assess injury to the pancreas and lung. We found that injection of L-arginine was followed by significant increases in plasma amylase and pancreatic myeloperoxidase accompanied by marked histopathological changes. The injury to the pancreas was slow to develop and peaked at 72 h. Subsequent to peak injury, the damaged areas contained collagen fibers as assessed by increased Sirius red staining. In contrast, D-arginine or other amino acids did not cause injury to the pancreas. In addition, acute inflammation in the pancreas was associated with lung injury. Our results indicate that administration of L-arginine to mice results in severe acute pancreatitis. This model should help in elucidating the pathophysiology of pancreatitis.     

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.     

Central role of neutrophil in the pathogenesis of severe acute pancreatitis

Severe acute pancreatitis (SAP) is an acute abdominal disease with the strong systemic inflammatory response, and rapidly progresses from a local pancreatic damage into multiple organ dysfunction. For many decades, the contributions of neutrophils to the pathology of SAP were traditionally thought to be the chemokine and cytokine cascades that accompany inflammation. In this review, we focus mainly on those recently recognized aspects of neutrophils in SAP processes. First, emerging evidence suggests that therapeutic interventions targeting neutrophils significantly lower tissue damage and protect against the occurrence of pancreatitis. Second, trypsin activation promotes the initial neutrophils recruitment into local pancreas, and subsequently neutrophils infiltration in turn triggers trypsin production. Finally, neutrophils have the unique ability to release neutrophil extracellular traps even in the absence of pathogens.     

TRAIL administration down-modulated the acute systemic inflammatory response induced in a mouse model by muramyldipeptide or lipopolysaccharide

The potent inducer of apoptosis TRAIL/Apo2 ligand is now under considerations in clinical trials for the treatment of different types of cancer. Since the natural history of cancer is often characterized by microbial infections, we have investigated the effect of recombinant human TRAIL in a mouse model of systemic acute inflammation of microbial origin represented by BALB/c mice treated with either bacterial muramyldipeptide (MDP) or lipopolysaccharide (LPS). When administered intraperitoneally (i.p.), these inflammatory bacterial compounds triggered a severe systemic inflammatory response within 2h, represented by body temperature elevation, increase of circulating serum amyloid-A (SAA) and of the number of leukocytes in the peritoneal cavity. Moreover, both MDP and LPS induced a significant elevation of the circulating levels of several inflammatory cytokines and chemokines. Noteworthy, pre-treatment with recombinant human TRAIL 48 and 72h before administration of either MDP or LPS, significantly counteracted all acute inflammatory responses, including the elevation of key pro-inflammatory cytokines/chemokines such as IL-1α, IL-6, G-CSF, MCP-1. These data demonstrate for the first time that TRAIL has a potent anti-inflammatory activity, which might be beneficial for the anti-tumoral activity of TRAIL.     

Protective effects of gabexate mesilate (FOY) against impaired pancreatic energy metabolism in rat acute pancreatitis induced by caerulein.

A supramaximal dose of caerulein (5 micrograms/kg.hr for 3.5 hours) caused edematous acute pancreatitis in rats, characterized by portal hyperamylasemia (32 +/- 3 U/ml) and pancreatic edema (pancreatic water content, 86 +/- 2%) [control group: amylase, 8 +/- 1 U/ml; water content, 74 +/- 2%]. In this model, increased portal levels of malate dehydrogenase (148 +/- 25 U/ml), increased mitochondrial fragility and impaired pancreatic energy charge level (0.77 +/- 0.05) were also observed [control group: malate dehydrogenase, 54 +/- 11 U/ml; energy charge level, 0.94 +/- 0.03]. Administration of gabexate mesilate, FOY, in a dose of 50 mg/kg.hr for 2 hours before and during the caerulein infusion had a significant protective effect against these pancreatic injuries (portal amylase level, 11 +/- 2 U/ml; MDH level, 72 +/- 19 U/ml; E.C., 0.89 +/- 0.02; water content, 76 +/- 2%). FOY in a dose of 20 mg/kg.hr was partially protective. These results indicate that subcellular organelle fragility and malfunction are closely related to the pathogenesis of acute pancreatitis and suggest the usefulness of FOY in the treatment of this disease.