Peritoneal macrophage activity after laparoscopy or laparotomy

Background/purpose: The beneficial effect of laparoscopy on the immune system seems not to be present at the peritoneal level at which the local immunity appears to be impaired by CO2. The aim of this study was to investigate the peritoneal macrophages (MPhis) activity after laparoscopy and laparotomy.

Methods: Thirty rats (300 to 350 g) were used and divided into 3 groups. In the laparotomy group, the peritoneum was opened and the abdominal wall exposed to air for 60'. In the laparoscopy group, pneumoperitoneum was created and maintained at 4 to 6 mm Hg for 60'. In the control group, anaesthesia was maintained for 60' without any other manipulations. Twenty-four hours after operation, peritoneal MPhis were harvested and cultured. The authors investigated nitrite/nitrate (NOx) production as well as the message for the inducible nitric oxide (iNOS), with the reverse transcriptase polymerase chain reaction under basal condition and after Lipopolysaccharide (LPS) stimulation.

Results: Basal MPhi NOx release was significantly higher after laparoscopy than either after laparotomy or control. LPS stimulation produced a strong increase in NOx production in laparotomy MPhis and control MPhis. In contrast, the increase in NOx production was markedly reduced in MPhi harvested after laparoscopy. Similar results were obtained for macrophage mRNA for iNOS; indeed, the increase in iNOS mRNA after LPS stimulation was blunted severely in MPhi from laparoscopy group.

Conclusions: MPhis after laparoscopy display an higher basal immune performance. After a second insult (LPS), they display a state of tolerance or desensitisation (blunted NOx production and reduced mRNA expression). This observation could have important implications in considering laparoscopy in patients with malignancy or sepsis.