Peritoneal macrophage and blood monocyte functions after open and laparoscopic-assisted cecectomy in rats

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Abstract
Background: It has been well established that open abdominal surgery results in systemic immunosuppression postoperatively; in contrast, laparoscopic surgery is associated with significantly better preserved systemic immune function. However, when intraperitoneal (local) immune function is considered, laparoscopic procedures done under a CO_2 pneumoperitoneum (pneumo) have been shown to result in greater immunosuppression compared to that of open surgery. Few studies have simultaneously assessed systemic and local immune function. The purpose of this study was to assess peripheral blood mononuclear cell (PBMC) and peritoneal macrophage tumor necrosis factor-α (TNF-α) levels, H_2O_2 production, and MHC class II antigen expression after open and laparoscopically assisted cecectomy in a rat model. Methods : A total of 75 Sprague Dawley rats were used for three separate experiments. For each study, rats were randomly divided into three groups: anesthesia alone (AC), laparoscopic-assisted cecectomy (LC), and open cecectomy via full laparotomy (OP). A CO_2 pneumo was used for laparoscopic operations. On postoperative day 1 the animals were sacrificed, macrophages were harvested via intraperitoneal lavage, and PBMCs were isolated from whole blood obtained by cardiac puncture. In experiment 1, macrophages and PBMC from each animal were stimulated with lipopolysaccharide, after which TNF-α levels of the supernatant were determined. In experiment 2, after stimulation with PMA, H_2O_2 release was assessed by measuring fluorescence. In experiment 3, via flow cytometry, the number of cells with surface MHC class II proteins were determined. Data from the three groups in each experiment were compared using analysis of variance Tukey-Kramer tests. Results : Macrophages and PBMC from mice in the OP group released significantly more TNF-α than cells from mice in the LC ( p < 0.05) or AC ( p < 0.05) groups. Macrophages from mice in the OP group released significantly less H_2O_2 than cells from the AC ( p < 0.01) and LC ( p < 0.05) groups. There was no difference between the AC and LC results. No significant differences in PBMC H_2O_2 release were noted among any of the groups. OP group macrophages expressed significantly less MHC class II antigen than did AC group macrophages ( p < 0.05). No differences were noted among the LC results and either the OP or AC group’s outcomes. No differences were noted in PBMC MHC class II expression among any of the groups. Conclusions : In all instances, the LC group’s macrophage results were similar to the AC group’s results. OC group macrophages produced significantly more TNF-α and less H_2O_2 than both the AC and LC groups. MHC class II protein expression was less for the OC group than for the AC group. OC group PBMCs produced more TNF-α. No differences in PBMC H_2O_2 release or MHC class II expression were noted. Laparoscopic methods better preserves the baseline values of the parameters studied.