Pancreatic Ascites as a Powerful Inducer of Inflammatory Cytokines

Abstract

Objectives: To determine if pancreatic ascites will induce interleukin 1β (IL-1β) or tumor necrosis factor α (TNF-α) production outside the pancreas and examine the possible components responsible. Design: Severe pancreatitis was induced in rats (n=30) by pancreatic duct infusion with 4% glycodeoxycholic acid; pancreatic ascites was collected 18 hours later. In vitro studies used quiescent murine splenic or pulmonary macrophages (10⁵/mL) which were exposed to media alone (control), trypsin, chymotrypsin, cathepsin-B, 20% ascites (vol/vol), 50% ascites, or endotoxin (lipopolysaccharide, 10 μg/mL, positive control) for 4 hours. Subsequently, pancreatic ascites was cultured for bacteria and assayed for endotoxin and cytokines (interleukin 1, interleukin 6, interleukin 8, TNF-α, or interferon γ). The experiments were then repeated using 20% and 50% ascites that was sterile and cytokine-free (SCF ascites). In vivo studies used 100% (n=8) or 50% (n=12) SCF ascites or normal rat serum (control, n=12) for a 10-second pulmonary lavage (100 μL) in adult mice, with lungs collected at 6 hours for cytokine gene analysis. Setting: Surgical basic science research laboratory. Main Outcome Measures: Interleukin 1β and TNF-α gene induction was assessed by quantitative competitive reverse-transcription polymerase chain reaction and cytokine protein production was determined by enzyme-linked immunosorbent assay. Results: Macrophages responded to untested and SCF ascites in a dose-dependent fashion, with a multifold increase in both IL-1β and TNF-α messenger RNA (mRNA) and protein, which was often more potent than lipopolysaccharide. Expression of IL-1β and TNF-α mRNA could not be induced by trypsin, chymotrypsin, or cathepsin-B. All animals undergoing lavage with 100% SCF ascites died within 2 hours, while those undergoing lavage with 50% SCF ascites showed a multifold increase in pulmonary IL-1β and TNF-α mRNA. Conclusions: Pancreatic ascites contains factors that are capable of inducing IL-1β and TNF-α production in vitro and in vivo. This effect cannot be reproduced by activated digestive enzymes and is propagated despite the absence of known inducers of cytokines such as bacteria, endotoxin, or other inflammatory cytokines. Arch Surg. 1997;132:1231-1236