Inflammatory response and bacterial dissemination after laparotomy and abdominal CO2 insufflation in a murine model of peritonitis.

BACKGROUND: The immunologic repercussions due to cavity insufflation are the focus of great discussion. The aim of this study was to compare the inflammatory response and bacterial dissemination after laparotomy and abdominal CO2 insufflation in a murine model of peritonitis. METHODS: Swiss mice were inoculated intraperitoneally with 0.5 ml of a solution containing 1 x 10(8) colony-forming units (CFU)/ml of Escherichia coli and were divided into three groups as follow: control (anesthesia for 30 min), laparotomy (2.5-cm midline incision for 30 min), and CO2 pneumoperitoneum (CO2 cavity insufflation for 30 min). The number of leukocytes, CFU/ml counting, and the levels of interleukin (IL)-6, tumor necrosis factor-alpha (TNF-alpha), and IL-10 were evaluated in blood, peritoneal, and pleural fluid samples obtained at 90 min and 18 h after the procedures. RESULTS: The laparotomy group showed a greater bacterial dissemination to the blood, peritoneum, and pleural cavity and also greater neutrophil migration to the peritoneal cavity compared to the CO2 insufflated and control groups. The 24-h mortality was also significantly higher in the laparotomy group. The IL-6 levels showed a precocious rise in all groups submitted to bacterial inoculation at the 90-min time point. At the 18-h time point, IL-6 levels in the peritoneum were significantly higher in the laparotomy group than in the control or CO2 insufflated groups. At the same time, TNF-alpha levels were higher in the laparotomy and CO2 insufflated groups than in controls; IL-10 levels showed no differences among the groups. CONCLUSIONS: Our results suggest that cavity insufflation with CO2 is a more effective method of access, inducing less bacterial dissemination and also a less intense inflammatory response. Cavity insufflation with CO2 may present a good option for the surgical treatment of patients with bacterial peritonitis.

Mechanisms of allergen- and LPS-induced bone marrow eosinophil mobilization and eosinophil accumulation into the pleural cavity: a role for CD11b/CD18 complex.

OBJECTIVE: The mechanisms involved in bone marrow eosinophil emigration and recruitment to inflammatory sites are not fully understood. The involvement of CD11b/CD18 in marrow eosinophil release induced by lipopolysaccharide (LPS) or allergen was investigated in mice. METHODS: Eosinophil and neutrophil counts in the pleural cavity, blood and bone marrow were performed at different time intervals after the intrathoracic injection of LPS (250 ng/cavity) or ovalbumin (OVA, 12 microg/cavity; into actively sensitized mice) and compared to anti-CD11b/CD 18 (5C6, 1 mg/mouse) or anti-IL-5 (TRFK-5, 500 microg/kg) treated mice. RESULTS: LPS induced local eosinophil influx, that peaked within 24 h and that was preceded by a decrease in marrow eosinophils at 4 h. Antigenic challenge induced a decrease in marrow eosinophils within 4 h, followed by a long lasting pleural eosinophil accumulation and a persistent increase in marrow eosinophil numbers. Pretreatment with anti-CD11b/CD18 abolished LPS-induced neutrophil and eosinophil accumulation in the pleural cavity at 4 and 24 h, respectively. This pretreatment failed to modify neutrophil emigration from bone marrow, but significantly inhibited marrow eosinophil release at 4 h post-LPS or OVA challenge. Anti-IL-5 pretreatment failed to inhibit LPS-induced pleural eosinophil accumulation and mobilization from bone marrow, but it abolished allergen-induced effects, indicating a role for IL-5 in marrow eosinophil mobilization induced by antigen, but not by LPS challenge. CONCLUSIONS: Our results suggest that eosinophil migration induced by antigen or LPS into the pleural cavity is preceded by bone marrow eosinophil release through a mechanism that depends on CD11b/CD18.

TSG-14 transgenic mice have improved survival to endotoxemia and to CLP-induced sepsis.

Tumor necrosis factor-stimulated gene 14 (TSG-14)/PTX3 was identified originally as a TNF-alpha and IL-1beta-stimulated gene from normal, human foreskin fibroblasts and vascular endothelial cells, respectively. TSG-14 gene encodes a 42-kDa-secreted glycoprotein with a carboxy-terminal half that shares homology with the entire sequence of C-reactive protein (CRP) and serum amyloid P component (SAP), acute-phase proteins of the pentraxin family. Some experimental evidence suggests that TSG-14 plays a role in inflammation, yet its function and mechanism of action remain unclear. We have generated transgenic mice that overexpress the murine TSG-14 gene under the control of its own promoter. From eight transgenic founders, two lineages were derived and better characterized: Tg2 and Tg4, carrying two and four copies of the transgene, respectively. TSG-14 transgenic mice were found to be more resistant to the endotoxic shock induced by LPS and to the polymicrobial sepsis caused by cecal ligation and puncture (CLP). Moreover, macrophages derived from the transgenic mice produced higher amounts of nitric oxide in response to IFN-gamma, TNF-alpha, and LPS as compared with macrophages from wild-type animals, and the augmented response appears to be the consequence of a higher responsiveness of transgenic macrophages to IFN-gamma. The data shown here are the first in vivo evidence of the involvement of TSG-14 in the inflammatory process and suggest a role for TSG-14 in the defense against bacterial infections.

A role for adrenoceptors in the regulation of pleural neutrophilia induced by LPS.

The role of catecholamines in regulating pleural neutrophilia evoked by intrathoracic (i.t.) injection of lipopolysaccharide (LPS) was investigated in Wistar rats by means of surgical adrenalectomy, depletion of catecholamine stores or adrenoceptor blockade. Treatment of animals with a single dose of LPS evoked a dramatic increase in the number of pleural neutrophils concomitant with an increase in the number of these cells in blood at 4 h. Although blood neutrophilia was drastically reduced when catecholamine stores were depleted with intraperitoneal (i.p.) injection of reserpine, pleural neutrophilia was not modified. However, the i.t. injection of reserpine reduced the increase in pleural neutrophils after LPS stimulation. Adrenalectomy failed to inhibit the increase in neutrophil counts in the blood or pleural cavity after LPS challenge. Pretreatment with intravenous (i.v.) injection of prazosin, an alpha(1)/alpha(2B) antagonist, reduced LPS-induced blood but not pleural neutrophilia. On the other hand, although pleural neutrophilia was not affected by systemic pretreatment with the alpha(2)-adrenoceptor antagonist, yohimbine, the local treatment (i. t. injection) with this antagonist markedly reduced the increase in pleural neutrophil counts observed after stimulation by LPS. In contrast, pleural neutrophilia induced by i.t injection of formyl-methionyl-leucyl-phenylalanine (fMLP) was not modified by local treatment with yohimbine. Taken together, our results suggest that catecholamines, through activation of alpha(1) and alpha(2)-adrenoceptors, play a role in the regulation of blood and pleural neutrophilia observed during the inflammatory response evoked by LPS in the pleural cavity.