EXPRESSION OF mRNA FOR CYTOKINES COMPARED TO THEIR CONCENTRATIONS IN CULTURE SUPERNATES OF U937 CELLS EXPOSED TO POLYCLONAL ACTIVATORS

Investigation of the cytokine expression dynamics as well as the cytokine-producing potential of immune-competent cells allows extensive studies of their functional characteristics. mRNAs encoding a number of cytokine genes are relatively stable, thus their level may be used as a marker for assessing the levels of activation and proliferation of immunocompetent cells as well as for evaluating the cytokine-producing potential of immunocompetent cells.

In our work, we assessed correlations between the levels of mRNA expression specific for IL-10, TNF-α, GM-CSF cytokines determined in a culture of differentiated macrophage U937 cells, and protein concentrations of the same cytokines as measured in supernates of U937 cell cultures, without and after exposure to polyclonal activators. The IL-10, TNF-α, GM-CSF mRNA expression was determined by real-time quantitative polymerase chain reaction. Protein concentrations of IL-10, TNF-α, GM-CSF cytokines in the culture supernatant of U937 cells were measured by an enzyme immunoassay. The use of an initially homogeneous cell culture in the study is convenient due to the identical conditions in all experimental variants.

The most pronounced effect of polyclonal activators is exerted upon production of GM-CSF mRNA, as well as protein concentration of this cytokine in the cell culture supernatants, thus actually coinciding with RT-qPCR results.  The TNF-α mRNA level decreased under the influence of polyclonal activators, whereas concentration of this cytokine was decreased in the cell supernate. The TNF-α protein in a culture medium did not reflect temporal changes in the cellular TNF-α mRNA expression, probably, due to potential decrease of cellular mRNA occurring by the feedback inhibitory mechanism. While the cytokines can accumulate and remain in the supernatant, the mRNA-related events leading to cytokine formation may be completed earlier. Therefore, the signalling pathways and cytokine release kinetics should be studied after establishing the time dependence at short time intervals, which may be individual for each cytokine.

Thus, the results of a study using polyclonal activators suggest that polyclonal activators applied as mitogens, have a significant effect upon the concentration of secreted IL-10, TNFα and GM-CSF. In this case, polyclonal activators affect the levels of mRNA encoded by cytokine genes, thus indicating transcriptional mechanisms of its action. But, in view of the fact that the data are ambiguous, in order to achieve greater correspondence between the changes in the studied proteins and specific mRNAs, a detailed description of the time dependence is required for the changes in mRNA contents.

cytokines, cell culture, linked immunosorbent assay, expression

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