Enhancement of peritoneal leukocyte function by granulocyte colony- stimulating factor in rats with abdominal sepsis

Abstract

Objective: To investigate the therapeutic effects of granulocte colony- stimulating factors (G-CSF) on thefunctional 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 spicific pathogen-free Sprague- Dawley rats. Interventions: Abdominal sepsis was introduced in rats by cecal ligation and puncture. The control animals received a sham operation. G-CSF (subcutaneous injection at 50 μg/kg or vehicle (100 μl 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 CD11 b/c and 18 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 microsphere 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 netrophils which may be one mechanism underlying its protective effect in abdominal sepsis.