The human intracellular interleukin 1 receptor antagonist promoter appropriately regulates gene expression in keratinocytes and gastrointestinal epithelial cells in vivo.

The 4555-bp promoter fragment for intracellular interleukin 1 receptor antagonist (4555-bp icIL-1Ra) has recently been demonstrated to regulate gene expression in a cell-type specific manner in vitro in transient transfection studies. To examine the activity of this promoter in vivo, transgenic mice possessing the 4555-bp promoter coupled to the E. coli lacZ reporter gene were created. Expression of endogenous icIL-1Ra and E. coli lacZ mRNA were examined in different tissues by RT-PCR, RNase protection assay and in situ hybridization. In transgenic mice both endogenous icIL-1Ra and E. coli lacZ were co-expressed by keratinocytes and by epithelial cells in different organs of the digestive system. The transgene was also expressed in the brain in four out of five lines, whereas endogenous icIL-1Ra was not detected in this organ. In contrast, only icIL-1Ra mRNA, but not E. coli lacZ mRNA, was detected in lipopolysaccharide (LPS)-stimulated resident peritoneal macrophages from icIL-1Ra promoter transgenic mice. These results indicate that a 4555-bp promoter fragment of human icIL-1Ra appropriately regulates gene transcription in keratinocytes and gastrointestinal epithelial cells in vivo. However, other as yet unidentified regulatory regions influence icIL-1Ra gene expression in macrophages following LPS stimulation.