Objective: To investigate the therapeutic effects of granulocyte colony-stimulating factor (G-CSF) on the functional activities of circulating and peritoneal neutrophils during intra-abdominal sepsis.
Design: Placebo, controlled study, using a rat model of intra-abdominal sepsis.
Setting: Animal research facility.
Subjects: Male specific pathogen-free Sprague-Dawley rats.
Interventions: Abdominal sepsis was produced in rats by cecal ligation and puncture. The control animals received a sham operation. G-CSF (subcutaneous injection at 50 microg/kg) or vehicle (100 microL of 5% dextrose) treatment was initiated at 1 hr after cecal ligation and puncture or sham operation and repeated at 12-hr intervals thereafter.
Measurements and main results: Six hours after cecal ligation and puncture, CD11b/c and CD18 expression on circulating neutrophils was significantly up-regulated when compared with those in the sham operated control animals. Peritoneal neutrophils exhibited a further up-regulation of these adhesion molecules than did the circulating neutrophils. A sustained up-regulation of CD11b/c and CD18 was found in peritoneal neutrophils even at 24 hrs after cecal ligation and puncture. G-CSF treatment increased CD11b/c expression on circulating neutrophils in 6-hr sham-operated rats, but did not further up-regulate CD11b/c or CD18 expression on circulating or peritoneal neutrophils in cecal ligation and puncture rats. Phagocytic activities of circulating neutrophils assessed by uptake of fluorescent latex microspheres were lower in 24-hr cecal ligation and puncture rats when compared with the sham-operated controls. G-CSF treatment prevented this inhibition. Furthermore, G-CSF enhanced the phagocytic activities of peritoneal neutrophils in both 6- and 24-hr cecal ligation and puncture rats when compared with those of the vehicle-treated animals. Spontaneous hydrogen peroxide generation by circulating neutrophils was increased in 6-hr cecal ligation and puncture rats, but not in 24-hr cecal ligation and puncture rats. Peritoneal neutrophils exhibited an inhibition of phorbol myristate acetate-stimulated hydrogen peroxide generation. G-CSF treatment did not up-regulate neutrophil hydrogen peroxide generation.
Conclusions: Circulating and peritoneal neutrophils exhibit marked polymorphism in their functional activities during the host response to abdominal sepsis. G-CSF treatment significantly enhanced the phagocytic function of both circulating and peritoneal neutrophils which may be one mechanism underlying its protective effect in abdominal sepsis.