Figure 4. Mechanism of hepatic acute phase gene activation following intra-abdominal insult. CO₂ pneumoperitoneum may attenuate this inflammatory response cascade by acting at any of a number of different steps: (1) CO₂ may cause local peritoneal cell acidosis, thus blocking the release of cytokines; (2) CO₂ may influence the clearance of circulating inflammatory mediators or alter cytokine–cytokine receptor interactions in the liver and elsewhere; or (3) hepatocytes may be affected directly by CO₂ via alterations in second messenger system function or transcription factor action.