Tissue-specific cytokine production during experimental acute pancreatitis. A probable mechanism for distant organ dysfunction.

Our purpose was to determine if cytokines are produced systemically during acute pancreatitis. Proinflammatory cytokines are elevated during acute pancreatitis and have been implicated in the progression of pancreatitis-associated multiple organ dysfunction. Whether these mediators are produced within all tissues or very few specific organs is not known. Edematous pancreatitis was induced in adult male mice by IP injection of cerulein. Necrotizing pancreatitis was induced in young female mice by feeding a choline-deficient, ethionine supplemented diet. Animals were sacrificed as pancreatitis worsened, with multiple organs prepared for tissue mRNA and protein analysis by RT-PCR and immunoblotting. Pancreatitis severity was established by histologic grading and serum amylase and lipase. There was no cytokine mRNA or protein detectable prior to the induction of pancreatitis. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1-beta (IL-1 beta) mRNA and protein were detected within the pancreas early in the course of pancreatitis in both models, coinciding with the development of hyperamylasemia (both P < 0.001). Interleukin-6 was produced in the pancreas after pancreatitis was more fully developed (P < 0.001). IL-1 beta and TNF-alpha were subsequently produced in large amounts in lung, liver, and spleen but never within kidney, cardiac muscle, or skeletal muscle. A significant delay between pancreatic and distant organ cytokine production was always observed. It is concluded that proinflammatory cytokines are produced within the pancreas and within organs known to develop dysfunction during severe pancreatitis. Cytokine production is tissue specific, correlates with disease severity, and occurs within the pancreas first and subsequently within distant organs.

Transgenic animals demonstrate a role for the IL-1 receptor in regulating IL-1beta gene expression at steady-state and during the systemic stress induced by acute pancreatitis.

Interleukin-1 (IL-1) gene expression is selectively induced in tissues involved in multisystem organ failure during acute pancreatitis, suggesting a role in the pathogenesis of distant organ dysfunction. This study was undertaken to investigate the mechanism of pancreatitis-induced end organ cytokine production and to better understand the processes by which IL-1 production is regulated. Seventy adult male transgenic mice in which the type 1 IL-1 receptor had been deleted by gene targeting in embryonic stem cells were utilized (homozygous -/- IL-1R knockout). Acute pancreatitis was induced by one of two methods: (A) IP injections of caerulein (50 microgram/kg/hr x 4) with animals sacrificed at 0, .5, 1, 2, 4, 6, and 8 hr; (B) 48-hr exposure to a choline deficient ethionine supplemented (CDE) diet with animals sacrificed at 0 and 72 hr. Knockout animals were compared to strain-specific control mice expressing the normal wild-type IL-1 receptor gene in which pancreatitis was similarly induced. The severity of pancreatitis was stratified by serum amylase, lipase, and blind histologic grading. IL-1 mRNA production was determined within the pancreas, lungs, liver, and spleen by quantitative differential RT-PCR. Deletion of the IL-1R1 attenuated the severity of pancreatitis, reaching statistical significance in the less severe edematous model. There was little or no constitutive expression of IL-1 mRNA within any of the tissues examined from wild-type animals; however, knockout animals showed elevated steady-state levels in each tissue. IL-1 mRNA became detectable in all tissues of wild-type animals shortly after either form of pancreatitis became apparent and increased significantly with worsening pancreatitis. Despite the attenuated pancreatitis, knockout animals produced significantly greater levels of IL-1 mRNA in each tissue, typically demonstrating a 30-50% increase over time matched IL-1 mRNA production in wild-type animals which was not pancreatitis model dependent. We conclude that genetic deletion of IL-1 receptors results in the overproduction of IL-1 mRNA in organs known to produce cytokines during pancreatitis even when the severity of pancreatitis is lessened. This suggests that a negative feedback loop exists between the IL-1 receptor and IL-1 gene expression.

Decreased mortality of severe acute pancreatitis after proximal cytokine blockade.

OBJECTIVE: This study determined the ability of interleukin-1 receptor antagonist (IL-1ra) to decrease the mortality of experimental acute pancreatitis. The response of the inflammatory cytokine cascade and its subsequent effects on pancreatic morphology were measured to determine the role of these peptides in mediating pancreatic injury. SUMMARY BACKGROUND DATA: Previous studies have shown that proinflammatory cytokines are produced in large amounts during acute pancreatitis and that blockade at the level of the IL-1 receptor significantly decreases intrinsic pancreatic damage. The subsequent effect on survival is not known. METHODS: A lethal form of acute hemorrhagic necrotizing pancreatitis was induced in young female mice by feeding a choline-deficient, ethionine supplemented (CDE) diet for 72 hours. For determination of mortality, the animals were divided into 3 groups of 45 animals each: control subjects received 100/microL normal saline intraperitoneally every 6 hours for 5 days; IL-1ra early mice received recombinant interleukin-1 receptor antagonist 15 mg/kg intraperitoneally every 6 hours for 5 days beginning at time 0; IL-1ra late mice received IL-1ra 15 mg/kg intraperitoneally every 6 hours for 3.5 days beginning 1.5 days after introduction of the CDE diet. A parallel experiment was conducted simultaneously with a minimum of 29 animals per group, which were sacrificed daily for comparisons of serum amylase, lipase, IL-1, IL-6, tumor necrosis factor-alpha, IL-1ra, pancreatic wet weight, and blind histopathologic grading. RESULTS: The 10-day mortality in the untreated control group was 73%. Early and late IL-1ra administration resulted in decreases of mortality to 44% and 51%, respectively (both p < 0.001). Interleukin-1 antagonism also was associated with a significant attenuation in the rise in pancreatic wet weight and serum amylase and lipase in both early and late IL-1ra groups (all p < 0.05). All control animals developed a rapid elevation of the inflammatory cytokines, with maximal levels reached on day 3. The IL-1ra-treated animals, however, demonstrated a blunted rise of these mediators (all p < 0.05). Blind histologic grading revealed an overall decrease in the severity of pancreatitis in those animals receiving the antagonist. CONCLUSIONS: Early or late blockade of the cytokine cascade at the level of the IL-1 receptor significantly decreases the mortality of severe acute pancreatitis. The mechanism by which this is accomplished appears to include attenuation of systemic inflammatory cytokines and decreased pancreatic destruction.