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

Abstract

Summary Differences in IL-1b mRNA expression, stability and translation between non-adherent monocytes and those stimulated by adherence suggest that cytokine regulation is coupled to the function and assembly of cytoskeletal structures. In situ hybridization studies were performed to visualize expression and positioning of IL-1b mRNA in adherently cultivated monocytes. IL-1b mRNA expression was heterogeneous with high transcript levels found in spread or polarized cells. Transcripts were compartmentalized to the perinuclear region in spread cells, and partially redistributed with polarization. In contrast to mRNA distribution in other motile cell populations, IL-1b mRNA did not localize to the distal or proximal actin cytoskeleton. Perinuclear confinement of transcripts required intact actin microfilaments. Treatment with cytoskeleton disruption and detergent extraction suggested that most non-translated IL-1b mRNA was associated with intermediate filaments. In monocytes stimulated by LPS, IL-1b, but not IL-1Ra transcripts were redistributed and partially associated, yet not bound to actin microfilaments. The present study demonstrates that IL-1b mRNA expression and localization in adherent monocytes is interrelated with the cytoskeletal rearrangement upon adherence, spreading and polarization.

A Novel Role of Vimentin Filaments: Binding and Stabilization of Collagen mRNAs

“…In another study, mRNAs for calcitonin generelated peptide in axons of neurons and interleukin 1␤ (IL-1␤) in monocytes were found associated with vimentin filaments (8,13). Unlike that of microtubules and microfilaments, however, the functional significance of association of mRNAs with intermediate filaments is not understood.…”

Intermediate filaments: A role in epithelial polarity

“…Finally, RNA localization and compartmentalization within the cytoplasm is yet another possible way to generate subcellular asymmetry. IFs have been shown to play a role in RNA localization and polarization in neurons [111], monocytes [112], and keratin-expressing frog oocytes [113,114,115].…”

Interactions Between Lipoxin A4, the Stable Analogue 16‐phenoxy‐lipoxin A4 and Leukotriene B4 in Cytokine Generation by Human Monocytes

“…One possible explanation to this could be the fact that our monocytes were purified without adherence. Adherence has been shown to induce cytokine production and to affect cytokine response to various agonists in monocytes [31,32]. Both 16-phe-LXA 4 and native LXA 4 caused a bell-shaped IL-6 response.…”

“…Dextran T-500 (Apoteksbolaget, Stockholm, Sweden), NycoPrep 1 1.068 gradient (Nycomed Pharma AS, Oslo, Norway), Hanks balanced salt solution (HBSS; Life Technologies, Inc., Gaithersburg, MD, USA) and the synthetic lipoxin analogue 16-phe-LXA 4 were designed and synthesized as in [26]; some materials and their manufacturers (within parentheses) are as follows: Native lipoxin A 4 and LTB 4 (Cascade Biochem Ltd, Reading, UK),Tri-ZOLreagent(LifeTechnologies,Inc,Gaithersburg, MD, USA), pd(N) 6 Isolation and culture of human peripheral blood monocytes. In order to obtain monocytes, purified by a method that confers minimal platelet contamination and does not involve adherence to a surface and thus activation [31,32], the following protocol was followed. EDTA anticoagulated venous blood was collected from healthy, medication-free volunteers.…”