Regulation of cytokine production in carcinoembryonic antigen stimulated Kupffer cells by beta-2 adrenergic receptors: implications for hepatic metastasis

Abstract

Elevated Carcinoembryonic antigen (CEA) levels in the serum indicate a poor prognosis for colorectal cancer patients. Induction of proinflammatory cytokines by CEA interaction with Kupffer cells has been proposed as a mechanism for hepatic metastasis formation. Studies show that the cytokine response in circulating and peritoneal macrophages is regulated by beta-adrenergic receptor signals, though little information is available regarding Kupffer cells. We investigated the relationship between beta-adrenergic receptor stimulation and the response of Kupffer cells to CEA. Comparisons between unstimulated and CEA stimulated rat Kupffer cells, using cDNA arrays, showed up-regulation (>4 fold) of the beta2-adrenergic receptor mRNA. Peak up-regulation occurred after 30 min with a decline at 1 h. We examined the effects of the specific beta2-adrenergic receptor agonist terbutaline on cytokine production by CEA stimulated rat Kupffer cells. Pre-treatment of Kupffer cells with terbutaline followed by CEA caused a significant increase in IL-6 and IL-10 production, but a significant reduction in TNF-alpha production (>3 fold). mRNA levels reflected those of the ELISA assays for IL-6 and IL-10 but not for TNF-alpha. For IL-6 and TNF-alpha, these changes were serum independent, while IL-10 was serum dependent. This response is different from LPS treated Kupffer cells where all three cytokines showed serum dependency. Overall, these data suggest that Kupffer cell stimulation by CEA is under beta-adrenergic receptor control and induction of the beta-receptor is an early event following CEA binding to its receptor. Control of TNF-alpha production is negatively affected by terbutaline, while that of IL-6 and IL-10 is positively controlled suggesting that very different beta-adrenergic receptor signaling pathways are involved.