ACS was induced in female Yorkshire swine, and peritoneal fluid was collected at the time of decompressive laparotomy. Naïve PMNs/monocytes were primed and/or activated with peritoneal fluid, phosphatidylcholine (PAF) plus peritoneal fluid, peritoneal fluid plus n-formyl-met-leu-phe (fMLP), and peritoneal fluid plus phorbol 12-myristate 13-acetate (PMA). Activation was determined by surface marker expression of integrins (CD11b an CD18) and selectins (CD62L). Additionally, proinflammatory cytokines in peritoneal fluid were analyzed.
Peritoneal fluid did not activate PMNs but increased CD11b expression on monocytes. When used as a primer for fMLP- or PMA-induced activation, peritoneal fluid significantly increased CD11b and CD18 expression on PMNs and monocytes. Peritoneal fluid collected at 6 and 12 h post decompressive laparotomy had similar effects. Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels were increased in peritoneal fluid.
Peritoneal fluid represents a primer for PMNs/monocytes and seems to act through receptor-dependent and receptor-independent pathways. Strategies to reduce the amount of peritoneal fluid may decrease the locoregional and systemic inflammatory response by reducing priming and activation of neutrophils/monocytes.