CO2 Modulates the Inflammatory Cytokine Release of Primary Human Pleural Macrophages

Background: It is well known that CO2 used during laparoscopy affects the peritoneal surface and local inflammatory response, including the inflammatory reactivity of peritoneal macrophages. However, little is known about the local effects of CO2 during thoracoscopy. In a previous study we have shown that in healthy adolescents, macrophages are the dominant cell population on the pleural surface. Therefore, we examined the effects of CO2 on the inflammatory response of primary human pleural macrophages. Methods: Human primary macrophages were harvested by lavage from healthy adolescents undergoing elective surgery for pectus bar correction (n = 8). After purification and 24 h resting, cells were incubated for 2 h in 100% CO2, 5% CO2 or 95% inert helium with 5% CO2 as hypoxic control. After incubation cells were stimulated with LPS for 4 h and 24 h. The release of TNF-alpha, IL-8, IL-6, IL-10 and IL-1 beta were determined by ELISA. Results: CO2, but not hypoxia, induced a significant reduction in the release of TNF-alpha and IL-8 as well as a significant increase in the release of IL-10 and IL-1 beta within the first 4 h after incubation. The levels of IL-6 and the release of cytokines at 24 h after incubation were not significantly affected. Conclusions: CO2 directly modulates the immediate inflammatory response of pleural macrophages. Therefore, CO2 insufflation during thoracoscopy could lower the local stress response, but does not appear to have a lasting effect.