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Dissociation between cytokine mRNA expression and protein production in shigellosis
R Raqib1, A Ljungdahl, A A Lindberg
1Division of Clinical Bacteriology, Karolinska Institutet, Huddinge Hospital, Sweden.
Abstract:
In our study, infection with Shigella dysenteriae type 1 (n = 16) or Shigella flexneri in adults (n = 5) was associated with a gradual accumulation of mRNA for interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, IL-6, transforming growth factor-beta, IL-10, IL-4, TNF-beta, interferon (IFN)-gamma and perforin in the rectal biopsy samples during the convalescent stage of the disease demonstrated by in situ hybridization. In contrast, immunohistochemical staining in rectal tissues of cytokine protein-producing cells at the single-cell level exhibited a steady-state expression during 2-36 days after the onset of the disease. The frequency of cytokine mRNA-expressing cells varied in the range of 3-100-fold higher than that of the corresponding protein-synthesizing cells. The accumulation of cytokine mRNA in vivo during shigellosis represented a long-lasting phenomenon throughout the disease course, and may be linked to its immunopathogenesis. The results also indicate that assessment of both protein and mRNA in vivo may provide complementary information. Stimulation in vitro of peripheral blood mononuclear cells from normal healthy donors with Shigella-derived lipopolysaccharide or shiga toxin was carried out to elucidate the role of Shigella antigens in the regulation of translation of cytokine-specific mRNA. The incidence of cytokine (IFN-gamma, IL-6 and TNF-alpha) mRNA- and cytokine protein-expressing cells was very similar and congruent after both these Shigella-derived stimuli. We could, thus, not find evidence for shiga toxin-induced down-regulation of cytokine mRNA translation as the explanation for the observed discrepancy between cytokine mRNA and protein levels in the tissue biopsies.
Insights
Shigella infection leads to prolonged accumulation of cytokine mRNA, but not protein, in rectal tissues. This suggests mRNA accumulation, not translation regulation, is key to shigellosis immunopathogenesis.
Area of Science:
- Immunology
- Microbiology
- Molecular Biology
Background:
- Shigellosis is an infectious disease caused by Shigella bacteria.
- Cytokines play a crucial role in the immune response to infection.
- Understanding the regulation of cytokine production is vital for managing shigellosis.
Purpose of the Study:
- To investigate the dynamics of cytokine mRNA and protein expression in rectal tissues during shigellosis.
- To explore the role of Shigella antigens in regulating cytokine mRNA translation.
Main Methods:
- In situ hybridization and immunohistochemistry were used to detect cytokine mRNA and protein in rectal biopsy samples.
- Peripheral blood mononuclear cells were stimulated in vitro with Shigella lipopolysaccharide and shiga toxin.
Main Results:
- Cytokine mRNA (including IL-1 beta, TNF-alpha, IL-6, IFN-gamma) gradually accumulated in rectal tissues during convalescence.
- Cytokine protein expression showed a steady-state pattern.
- The frequency of cytokine mRNA-expressing cells was significantly higher (3-100 fold) than protein-expressing cells.
- In vitro stimulation showed congruent mRNA and protein expression, refuting shiga toxin-induced translational down-regulation.
Conclusions:
- The accumulation of cytokine mRNA during shigellosis is a long-lasting phenomenon potentially linked to immunopathogenesis.
- Assessing both cytokine mRNA and protein provides complementary insights into the immune response.
- Shiga toxin does not appear to down-regulate cytokine mRNA translation in peripheral blood mononuclear cells.