Expression and localization of IL-1 beta mRNA is interrelated with cytoskeletal rearrangement in monocytes stimulated by adherence: A light microscopy in situ hybridization study

Differences in IL-1 beta mRNA expression, stability and translation between non-adherent monocytes and those stimulated by adherence suggest that cyto kine regulation is coupled to the function and assembly of cytoskeletal str uctures. In situ hybridization studies were performed to visualize expressi on and positioning of IL-1 beta mRNA in adherently cultivated monocytes. IL -1 beta mRNA expression was heterogeneous with high transcript levels found in spread or polarized cells. Transcripts were compartmentalized to the pe rinuclear region in spread cells, and partially redistributed with polariza tion. In contrast to mRNA distribution in other motile cell populations, IL -1 beta mRNA did not localize to the distal or proximal actin cytoskeleton. Perinuclear confinement of transcripts required intact actin microfilament s. Treatment with cytoskeleton disruption and detergent extraction suggeste d that most non-translated IL-1 beta mRNA was associated with intermediate filaments. In monocytes stimulated by LPS, IL-1 beta, but not IL-1Ra transc ripts were redistributed and partially associated, yet not bound to actin m icrofilaments. The present study demonstrates that IL-1 beta mRNA expressio n and localization in adherent monocytes is interrelated with the cytoskele tal rearrangement upon adherence, spreading and polarization.