Regulation of Spi 2.1 and 2.2 gene expression after turpentine inflammation: discordant responses to IL-6

The rat serine protease inhibitor (Spi) 2 gene family includes both positiv e (Spi 2.2) and negative (Spi 2.1) acute phase reactants. facilitating mode ling of regulation of hepatic acute phase response (APR). To examine the ro le of signal transducer and activation of transcription (STAT) proteins in the divergent regulation of these model genes after induction of APR, we ev aluated the proximal promoters of the genes, focusing on STAT binding sites contained in these promoter elements. Induction of APR by turpentine injec tion includes activation of a STAT3 complex that can bind to a gamma-activa ted sequence (GAS) in the Spi 2.2 gene promoter, although the Spi 2.2 GAS s ite can bind STAT1 or STAT5 as well. To create an in vitro model of APR, pr imary hepatocytes were treated with combinations of cytokines and hormones to mimic the hormonal milieu of the whole animal after APR induction. Incub ation of primary rat hepatocytes with interleukin (IL)-6, a critical APR cy tokine, leads to activation of STAT3 and a 28-fold induction of a chloramph enicol acetyltransferase reporter construct containing the -319 to +85 regi on of the Spi 2.2 promoter. This suggests the turpentine-induced increase o f Spi 2.2 is mediated primarily by IL-6. in contrast, although turpentine t reatment reduces Spi 2.1 mRNA in vivo and IL-6 does not increase Spi 2.1 mR NA in primary rat hepatocytes, treatment of hepatocytes with IL-6 results i n a 5.4-fold induction of Spi 2.1 promoter activity mediated through the pa ired GAS elements in this promoter. Differential regulation of Spi 2.1 and 2.2 genes is due in part to differences in the promoters of these genes at the GAS sites. IL-6 alone fails to reproduce the pattern of rat Spi 2 gene expression that results from turpentine-induced inflammation.