Meconium stimulates a pro-inflammatory response in peritoneal macrophages:Implications for meconium peritonitis

Background/Purpose: Although meconium peritonitis is a rare condition, the mortality rate can be as high as 40%. Meconium peritonitis is a result of i ntestinal perforation in utero, which leads to dense inflammation in the pe ritoneal cavity. The fetus has relatively immature peritoneal defense mecha nisms, so the cause of this dense inflammation is unclear. The peritoneal m acrophage is a key cell in the peritoneal inflammatory response in adults. The purpose of this investigation was to determine if sterile meconium had a direct stimulatory effect on the peritoneal macrophage. Methods: Peritoneal macrophages were harvested from adult C3H/HEN mice. The cells were placed in microtiter wells at 10(5) cells per well. Sterile hum an meconium was diluted in media and placed in the wells at varying concent rations for 8 hours. Lipopolysaccharide (LPS) (10 mu g/mL) served as a posi tive control. Supernatants were harvested and assayed for tumor necrosis fa ctor alpha (TNF-alpha) using a commercial ELISA kit. Separate cells were as sayed for TNF-alpha message using polymerase chain reaction (PCR). In anoth er series of experiments, procoagulant activity (PCA) was determined on fre eze-thawed cells using a two-stage amidolytic assay. To test for the role o f protein kinase C (PKC) in the PCA response H7, a PKC inhibitor, was used as well. Results: Meconium stimulation resulted in a significant increase in TNF-alp ha compared with negative controls with a peak at 0.1% meconium (121 pg/mL v 11 pg/mL, P < .05). There was a significant increase in PCA, with a 10-fo ld increase with 1% meconium compared with controls (P < .05). This respons e was limited to less than 5% by PKC inhibition. Conclusions: Sterile meconium results ina marked proinflammatory response i n the peritoneal macrophage with elevations of both PCA and TNF-alpha. The TNF response is likely mediated at a pretranscriptional level because there is a marked increase in TNF mRNA. These data suggest that the PCA response is regulated by a PKC mechanism similar to LPS. Stimulation of the periton eal macrophage by meconium is a possible cause of the marked inflammation s een in meconium peritonitis. J Pediatr Surg 34:214-217. Copyright (C) 1999 by W.B. Saunders Company.