The interleukin-1-related cytokine IL-1F8 is expressed in glial cells, but fails to induce IL-1β signalling responses

Messenger RNA for IL-1F8 was detected in neurons and glia (microglial cells, oligodendrocytes progenitor cells and to a lesser extent astrocytes) by RT-PCR. Bacterial lipopolysaccharide (LPS) had no effect on IL-1F8 mRNA levels in mixed glial cultures. Recombinant mouse IL-1β induced strong activation of ERK1/2, p38, JNK and NFκB, and significant release of IL-6 and PGE2, which was blocked by IL-1ra. In contrast, recombinant mouse IL-1F8 did not influence any of these parameters. These results demonstrate that CNS cells may be a source of IL-1F8, but the failure of LPS to modulate IL-1F8 mRNA expression, and of recombinant IL-1F8 to induce any of the classical IL-1 responses, suggest that this cytokine has restricted activities in the brain, or that it may act via alternative pathway(s).