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Poliovirus infection interferes with the phorbol ester-induced differentiation of the monocytic U937 cell line
J A López-Guerrero1, C Cabañas, C Bernabeu
1Centro de Biología Molecular, Universidad Autónoma CSIC, Madrid, Spain.
Abstract:
Monocytic U937 cells can differentiate in vitro into macrophage-like cells by treatment with phorbol esters such as phorbol 12-myristate 13-acetate (PMA). We have analyzed the effect of poliovirus infection in this pathway of differentiation. Poliovirus RNA replication took place in both untreated and PMA-treated U937 cells infected before or after PMA addition, although a slight reduction in poliovirus RNA levels was observed in PMA-treated cells at late times postinfection. Total protein synthesis remained unchanged during the first 5 h of infection both in normal and PMA-treated cells. However, an inhibition on total RNA synthesis was observed early in infection. PMA-induced c-myc mRNA expression was abolished when infection took place 1 h before PMA addition but was just partially inhibited when poliovirus was added 1 h after PMA stimulation. Fluorescence flow cytometry analysis revealed that poliovirus infection induced an increase in the number of 4F2 molecules per cell in normal U937 cells and a slight decrease in the number of positive cells for the antigens CD14, CD4 and CD11c in both untreated or PMA-treated U937 cells. These findings suggest that poliovirus infection of U937 cells interferes at various levels with monocyte maturation yielding cells which are unable to undergo the complete pathway of differentiation to macrophages.
Insights
Poliovirus infection disrupts the differentiation of U937 monocytic cells into macrophages. This viral infection impacts cellular processes, hindering the maturation of these immune cells.
Area of Science:
- Cell Biology
- Virology
- Immunology
Background:
- Monocytic U937 cells differentiate into macrophage-like cells upon phorbol ester (PMA) treatment.
- Poliovirus infection is studied for its impact on cellular differentiation pathways.
Purpose of the Study:
- To investigate how poliovirus infection affects the PMA-induced differentiation of U937 cells into macrophages.
- To identify specific molecular and cellular changes induced by poliovirus during monocyte maturation.
Main Methods:
- U937 cells were treated with PMA to induce differentiation.
- Cells were infected with poliovirus before or after PMA addition.
- Poliovirus RNA replication, total protein and RNA synthesis were measured.
- c-myc mRNA expression was analyzed.
- Flow cytometry was used to assess cell surface markers (4F2, CD14, CD4, CD11c).
Main Results:
- Poliovirus RNA replicated in both untreated and PMA-treated cells, with a slight reduction in PMA-treated cells late post-infection.
- Early inhibition of total RNA synthesis was observed.
- PMA-induced c-myc mRNA expression was abolished or partially inhibited depending on infection timing relative to PMA.
- Poliovirus infection increased 4F2 molecules and decreased CD14, CD4, and CD11c expression.
Conclusions:
- Poliovirus infection interferes with U937 cell differentiation into macrophages at multiple levels.
- The infection yields cells with impaired maturation, unable to complete the differentiation pathway.