Carbon dioxide directly suppresses spontaneous migration, chemotaxis, and free radical production of human neutrophils.
BACKGROUND
Carbon dioxide (CO(2)) insufflation during laparoscopy has been shown to dampen the systemic stress response to surgery. This is related to a suppression of peritoneal macrophage functions. In vivo data suggest that CO(2) can also affect neutrophils (polymorphonuclear cells, PMNs), the most abundant cell type in the inflamed peritoneal cavity. Nonetheless, the direct effects of CO(2) on PMNs have not yet been investigated.


METHODS
PMNs were isolated from peripheral blood of healthy volunteers and incubated with (1) CO(2) (100% CO(2), pH 6.2), (2) hypoxic control (95% helium/5% CO(2), pH 7.4), and (3) control (95% air/5% CO(2), pH 7.4). Spontaneous and IL-8-induced migrations (chemokinesis and chemotaxis) during 2 h of exposure to different gases were measured with a transwell chamber system. The release of reactive oxygen species (ROS, luminometry) was determined after 15-min and 2-h exposures. In other sets of experiments, PMNs were exposed for 2 h or 4 h and kept under normal conditions for 18 h with lipopolysaccharide (LPS) stimulation thereafter. Final viability and apoptosis were assessed with fluorometry.


RESULTS
Exposure to 100% CO(2) completely blocked spontaneous and IL-8 induced migration of PMNs (p < 0.001 vs. controls). Neutrophil migration was slightly diminished in the hypoxic control group. PMA-stimulated ROS production was reduced even after short exposure to 100% CO(2)(p < 0.05). We observed a slight increase of caspase-3/7 activity after exposure to 100% CO(2) and/or hypoxia; however, total viability was not affected.


CONCLUSIONS
CO(2) incubation directly and temporarily suppresses the proinflammatory functions of PMNs; this is caused only partially by the concomitant hypoxia. This effect will contribute to the dampened inflammatory response to laparoscopic surgery. Further studies are needed to investigate whether the temporary suppression of neutrophil functions could affect the clearance of bacterial contaminations.
Shimotakahara
Akihiro
A
Department of Pediatric Surgery, Hannover Medical School, Carl-Neuberg-Str.1, D-30625, Hannover, Germany. shimo@med.juntendo.ac.jp
Kuebler
Joachim F
JF
Vieten
Gertrud
G
Kos
Marcin
M
Metzelder
Martin L
ML
Ure
Benno M
BM
D017209:Apoptosis / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D002465:Cell Movement / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D005609:Free Radicals / Q000378:metabolism*; D006801:Humans; D009504:Neutrophils / Q000378:metabolism / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism
D005609:Free Radicals; D017382:Reactive Oxygen Species; D002245:Carbon Dioxide