Abstract

Human peripheral blood mononuclear cells analyzed immediately after isolation did not express detectable mRNA for interleukin-1 beta (IL-1 beta). In the strict absence of lipopolysaccharide (LPS), incubation in glass or plastic resulted in expression of IL-1 beta mRNA without detectable IL-1 beta synthesis, even when cells were incubated for 20 h. The accumulation of IL-1 beta mRNA was most likely due to adherence since rotating the containers reduced the amount of mRNA. However, the cells were "primed" by 3 h adherence since subsequent stimulation with LPS resulted in more IL-1 beta (214%) 4 h after stimulation compared to freshly obtained, LPS-stimulated cells. Ratios of IL-1 beta mRNA induced by LPS versus adherence were 7.8, 36, and 20 at 4, 12, and 24 h, respectively; the corresponding ratios for IL-1 beta protein were 18, 160, and 180. Comparing Staphylococcus epidermidis versus LPS, the ratios of IL-1 beta mRNA were 3.2, 0.5, and 1.2 at 4, 8, and 24 h, respectively, however, the corresponding ratios for IL-1 beta protein were 65, 22, and 10. The differences in transcription versus translation in these studies are unlikely due to changes in stability of mRNA since the half-life of adherence-induced IL-1 beta mRNA was 2.5 versus 4 h for LPS-induced mRNA. There was also no evidence of superinduction of mRNA in peripheral blood mononuclear cells stimulated with LPS, whereas, tumor necrosis factor alpha mRNA was elevated in the presence of cycloheximide. Using different methods of cell surface stimulation, our results demonstrate that synthesis of IL-1 beta is regulated by at least two separate mechanisms, one at the level of transcriptional activation and the other one involving translational efficiency.

Highlights

  • Human peripheral blood mononuclear cells analyzed immediately after isolation did not express detectable mRNA for interleukin- l/3 (IL- 1s)

  • We investigated the regulation of IL-l@ expression in human peripheral blood mononuclear cells (PBMC) by performing Northern blot analysis and measuring its synthesis by specific radioimmunoassay

  • We consistently observed no evidence of IL-l@ synthesis despite the accumulation of mRNA

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Summary

Introduction

Human peripheral blood mononuclear cells analyzed immediately after isolation did not express detectable mRNA for interleukin- l/3 (IL- 1s). Ratios of IL-Q3 mRNA induced by LPS versus adherence were 7.8, 36, and 20 at 4, 12, and 24 h, respectively; the corresponding ratios for IL-la protein were 18, 160, and 180. Comparing Staphylococcus epidermidis versus LPS, the ratios of IL-10 mRNA were 3.2, 0.5, and 1.2 at 4, 8, and 24 h, respectively, the corresponding ratios for IL-l/3 protein were 65, 22, and 10. The differences in transcription versus translation in these studies are unlikely due to changes in stability of mRNA since the half-life of adherence-induced. Using different methods of cell surface stimulation, our results demonstrate that synthesis of IL-la is regulated by at least two separate mechanisms, one at the level of transcriptional activation and the other one involving translational efficiency. Prostaglandins suppress IL-1 production without affecting the accumulation of IL-1 mRNA [9]

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