At thermoneutral conditions, high steady-state levels of transcripts for both IL-1α and its receptor IL-1RtI were found in specialized thermogenic organ, brown adipose tissue (BAT) of adult mice, as compared with the levels in lymph nodes, brain and spleen. A pronounced decrease of IL-1α mRNA level in BAT was observed after lipopolysaccharide (LPS) administration and after exposure to cold. Likewise, LPS decreased the IL-1 RtI mRNA level and depressed also the expression of cold-inducible genes for the BAT-specific heat-producing uncoupling protein and for lipoprotein lipase. It is concluded that, besides the centrally-mediated effects, there exists a direct peripheral interaction of IL-1 cytokines with BAT cells.
