Interferon‐α but not ‐β Genes Require De Novo Protein Synthesis for Efficient Expression in Human Monocytes

This is the authors' abstract. We don't add key points for this paper.

Monocytes produce interferon-alpha (IFN)-alpha) and -beta when human peripheral blood mononuclear cells (PBMCs) are stimulated in vitro by Sendai virus (SV). We found that about 70% of the IFN-producing cells (IPCs) expressed both IFN-alpha and -beta mRNA; the rest expressed only IFN-beta mRNA. In the presence of the protein synthesis inhibitor cycloheximide (CHX), the frequency of IFN-alpha mRNA-containing cells, measured after 6h, was decreased by 85-90%. Results of nuclear run-on transcription assays showed that CHX inhibited IFN-alpha gene expression. The frequency of IFN-beta mRNA-containing cells was not reduced by CHX. Actually, a threefold increase was observed at the lower CHX concentrations. Studies on the kinetics of IFN-alpha/beta mRNA induction showed that CHX accelerated the appearance of IFN-beta mRNA-containing cells, increased IFN-beta mRNA levels, and delayed the normally occurring post-inductional decrease of IFN-beta mRNA. Unexpectedly, an initially normal or even accelerated IFN-alpha mRNA response was seen in the presence of CHX during the first 3-4 h after SV stimulation. This occurred in a small proportion of the potential IPCs. However, CHX prevented the subsequent marked increase of IFN-alpha mRNA levels. Preincubation of PBMCs for 6 h in conditioned medium (CM) containing IFN and other cytokines prevented the CHX-mediated inhibition of IFN-alpha mRNA. Without preincubation this was not seen. The preincubation in CM caused an accelerated appearance of IFN-alpha mRNA, resembling that of IFN-beta mRNA. The results suggest that IFN-alpha and -beta genes are differentially regulated in the same monocytes, the former requiring de novo synthesis of intracellular protein(s) for efficient expression.