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IL-4 regulation of p38 MAPK signalling is dependent on cell type
Abigail E Hunt1, Lynn M Williams, Ferdinand V Lali
1UCSF Cancer Center, 2340 Sutter Street, 94115, USA.
Abstract:
p38 MAPK was originally characterized as a stress-induced kinase, along with JNK. Subsequently, p38 MAPK was found to be activated by stimuli other than cellular stress, such as growth factors and mitogens, like interleukin (IL)-2, IL-7 and IL-3. A notable exception was IL-4, as studies in mast cells showed no activation of p38 MAPK by this cytokine. In this study we show that the regulation of p38 MAPK is cell type dependent. Like other cytokines that signal through the gamma (gamma)(c), IL-4 can activate p38 MAPK in the CT6 T-cell line and BA/F3 pro-B-cells. However, IL-4 was unable to activate p38 MAPK in the murine macrophage cell line, RAW 264.7 and, indeed, prolonged exposure of cells to IL-4 results in suppression of LPS-induced MAPK activation. This result correlates with the well defined inhibitory effect of IL-4 on tumour necrosis factor alpha (TNFalpha) production. In contrast, studies in primary human monocytes showed that prolonged exposure to IL-4 resulted in enhanced activation of LPS-stimulated p38 MAPK; this correlated with an enhanced TNFalpha production. These data highlight the complexity of IL-4 signalling mechanisms, the diversity that can exist in the regulation of a given signalling pathway by a given cytokine and, furthermore, indicate the problems that can arise from extrapolation between different cell systems.
Insights
Interleukin-4 (IL-4) signaling pathways regulating p38 MAPK activation are cell-type dependent, impacting tumor necrosis factor alpha (TNFα) production differently across various cell lines and primary cells.
Area of Science:
- Cellular and Molecular Biology
- Immunology
- Signal Transduction
Background:
- p38 Mitogen-Activated Protein Kinase (MAPK) is activated by stress, growth factors, and cytokines like IL-2, IL-7, and IL-3.
- Interleukin-4 (IL-4) was previously thought not to activate p38 MAPK, based on studies in mast cells.
Purpose of the Study:
- To investigate the cell-type specificity of p38 MAPK regulation by IL-4.
- To understand the implications of IL-4's diverse effects on p38 MAPK activation for cytokine production.
Main Methods:
- Utilized CT6 T-cell lines, BA/F3 pro-B-cells, RAW 264.7 macrophage cell lines, and primary human monocytes.
- Stimulated cells with IL-4 and lipopolysaccharide (LPS) to assess p38 MAPK activation.
- Measured tumor necrosis factor alpha (TNFα) production in response to IL-4 treatment.
Main Results:
- IL-4 activated p38 MAPK in CT6 T-cells and BA/F3 pro-B-cells, but not in RAW 264.7 macrophages.
- In RAW 264.7 cells, IL-4 suppressed LPS-induced p38 MAPK activation and TNFα production.
- In primary human monocytes, IL-4 enhanced LPS-stimulated p38 MAPK activation and TNFα production.
Conclusions:
- p38 MAPK regulation by IL-4 is highly cell-type dependent.
- Extrapolation of findings between different cell systems can be problematic due to signaling diversity.
- IL-4 exhibits complex signaling mechanisms influencing immune responses.