Interleukin-1 receptor accessory protein transcripts in the brain and spleen: kinetics after peripheral administration of bacterial lipopolysaccharide in mice.

Receptors for IL-1, type I (IL-1R1) and type II (IL-1R2), have been characterized by pharmacological and molecular techniques in the mouse brain. High densities are mainly found in the cortex, dentate gyrus and choroid plexus. It was therefore of interest to investigate the expression of mRNA IL-1 receptor accessory protein (IL-1R AcP), which is a part of the IL-1 receptor complex and has been shown to interact specifically with IL-1R1. IL-1R AcP transcripts were detected under basal conditions following RT-PCR amplification in the mouse brain, as well as in the pituitary, spleen, adrenal and liver. IL-1R AcP transcripts were found in higher amounts than IL-1R1 transcripts in all tissues except the spleen, where their expression was minor. Following bacterial lipopolysaccharide (LPS) stimulation (3-48 h), IL-1R AcP transcripts were not changed in the brain, while IL-1R1 transcripts were increased for 3-6 h. In the spleen, a slight increase in IL-1R AcP and IL-1R1 was observed during the first hours following LPS stimulation. In conclusion, IL-1R AcP mRNA is expressed in the brain and in other tissues where IL-1R1 transcripts are found. However, the regulation of its expression is distinct from IL-1R1. The high level of expression and the lack of regulation of IL-1R AcP transcripts in the brain under inflammatory conditions suggest that the protein might be constitutively expressed in excess.