Acute pancreatitis induces cytokine production in endotoxin-resistant mice

Abstract

Objective: The purpose of this study was to determine whether pathologic progression and cytokine responses in acute pancreatitis (AP) are altered in the absence of endotoxemia.

Summary background data: Previous studies have demonstrated that AP is characterized by rapid production and release of inflammatory cytokines, which play a major role in the local pancreatic and systemic complications of this disease. Infection and endotoxemia have been implicated as a major source of morbidity and death in AP and as possible stimuli for the overwhelming cytokine response seen in this disease.

Methods: AP was induced by a choline-deficient and ethionine-supplemented diet for 4 days in normal C57BL/6J mice (controls, n = 23) and in CD14 knockout mice (CD14KO, n = 23), which cannot produce circulating cytokines in response to endotoxin. Control and endotoxin-resistant mice were killed at time 0, then at 24, 48, 72, and 96 hours after the start of the diet. At each time point serum was collected for amylase, glucose, and cytokine measurements (tumor necrosis factor-alpha [TNFalpha] and interleukin-1beta [IL1beta]), and the pancreas was removed for histologic examination. TNFalpha was measured with a bioassay using WEHI-2F cells and IL1beta with a bioassay using D10.G4.1 cells.

Results: CD14KO mice developed biochemical manifestations of AP with alterations in amylase levels, hypoglycemia, weight loss, and histologic changes of pancreatitis similar to the pattern seen in control mice. TNFalpha and IL1beta production had similar kinetics in both groups, with significant peak TNFalpha serum levels at 72 hours and a progressive rise of IL1beta levels throughout the study period. Histologic changes appeared earlier and were more pronounced in the control versus the CD14KO mice. However, the mortality rate was identical (20% at 96 hours) for both groups.

Conclusions: These results demonstrate that the progression of AP, the cytokine response associated with the disease, and early death are independent of endotoxin action. These findings, which suggest that an uncharacterized stimulus is responsible for triggering the cytokine cascade in this disease, may have significant implications for the management of patients with AP.