Prostaglandin E2 production during hepatic regeneration downregulates Kupffer cell IL-6 production

The liver possesses the remarkable ability to regenerate to its original size after a 70% partial hepatectomy. There has been little effort to characterize the Kupffer cells' role in this unique mammalian reparative physiologic phenomenon. The capacity of rat Kupffer cells (KC) isolated at specific intervals after partial hepatectomy to produce interleukin-6 (IL-6) and prostaglandin E2 (PGE2) in response to endotoxin was evaluated in standard RPMI-1640 (1200 microM L-arginine) and arginine-depleted RPMI-1640 (10 microM L-arginine) media. Regenerating liver KC 48 to 120 hours after partial hepatectomy responded to endotoxin stimulation with a significantly greater (p less than 0.05) production of IL-6 in standard RPMI-1640. Because Kupffer cells function in an environment where high arginase activity results in negligible L-arginine levels, the 10 microM L-arginine RPMI-1640 was used to simulate the true hepatic microenvironment. Production of IL-6 by regenerating liver KC was further increased (p less than 0.05) by placing these same KC in 10 microM L-arginine RPMI-1640 tissue culture media. During the same period, regenerating liver KC produced significantly (p less than 0.01) more PGE2 than sham-operated KC in both standard and low-arginine media. When the cyclo-oxygenase inhibitor indomethacin (1 x 10(-5) M) was added to cultures, the PGE2 production was inhibited, and IL-6 production was upregulated (p less than 0.05) in arginine-depleted cultures. The authors conclude that during hepatic regeneration KC IL-6 production is elevated but controlled in an autoregulatory fashion by KC PGE2 production.