Different signal pathways regulate IL-1β-induced mature and primary miRNA-146a expression in human alveolar
1Xi'an Jiaotong University Department of Genetics and Molecular Biology, School of Medicine 76 Yanta West Road Xi'an, Shaanxi 710061 China University of Manchester NIHR Translational Research Facility in Respiratory Medicine Group, School of Translational Medicine Manchester UK.
Abstract:
It was known that IL-1β-induced rapid expression of miR-146a, which regulated the secretion of inflammatory chemokines in human A549 alveolar epithelial cells. However, little is known about the level of primary miR-146a and the downstream biogenesis of miR-146a in A549 cells. We examined the levels of primary miR-146a and mature miR-146a in A549 cells following treatment with pharmacological inhibitors of IKK-2 (TPCA-1), MEK-1/2 (PD098059), JNK-1/2 (SP600125), p38 MAPK (SB 203580) and PI-3k (LY294002). Our studies showed that exposure to PD98059, TPCA-1 and LY294002 resulted in a dose-dependent reduction in the expression of mature miR-146a while the primary miR-146a expression was not changed by any inhibitor. Western blot showed that IL-1β induced an increase of TRBP at 30 min, following by an extended expression at 24 h compared to the non-IL-1β controls in A549 cells. In conclusion, our studies indicated that miR-146a expression in alveolar epithelial cells was regulated at the post-transcriptional level via a MEK-1/2 and IKK2 pathway, and also for the first time via PI-3k pathway. The longer expression of TRBP following stimulation with IL-1β suggests that TRBP might play a role in the process of regulating the processing of primary miR-146a to mature miR-146a in human alveolar epithelial cells.
Insights
Interleukin-1 beta (IL-1β) triggers microRNA-146a (miR-146a) expression in lung cells via MEK/IKK2 and PI3K pathways. This regulation occurs post-transcriptionally, impacting inflammatory chemokine secretion.
Area of Science:
- Molecular Biology
- Cell Biology
- Immunology
Background:
- Interleukin-1 beta (IL-1β) is known to induce microRNA-146a (miR-146a) expression in human A549 alveolar epithelial cells, regulating inflammatory chemokines.
- The precise mechanisms controlling primary miR-146a levels and its downstream biogenesis in these cells remain largely uncharacterized.
Purpose of the Study:
- To investigate the regulatory pathways involved in miR-146a biogenesis in A549 cells.
- To determine the role of specific signaling pathways (MEK, IKK-2, JNK, p38 MAPK, PI-3k) in the post-transcriptional regulation of miR-146a.
- To examine the expression of TAR RNA-binding protein (TRBP) in response to IL-1β stimulation.
Main Methods:
- A549 cells were treated with pharmacological inhibitors targeting IKK-2 (TPCA-1), MEK-1/2 (PD098059), JNK-1/2 (SP600125), p38 MAPK (SB 203580), and PI-3k (LY294002).
- Quantitative analysis of primary and mature miR-146a expression levels.
- Western blot analysis was used to assess TRBP protein levels following IL-1β stimulation.
Main Results:
- Inhibition of MEK-1/2, IKK-2, and PI-3k pathways led to a dose-dependent decrease in mature miR-146a expression.
- Primary miR-146a expression levels were unaffected by any of the tested inhibitors.
- IL-1β stimulation resulted in an early increase and sustained expression of TRBP in A549 cells.
Conclusions:
- miR-146a expression in alveolar epithelial cells is regulated post-transcriptionally via MEK-1/2, IKK2, and PI-3k signaling pathways.
- The sustained expression of TRBP suggests its potential involvement in the processing of primary miR-146a to mature miR-146a in human alveolar epithelial cells.
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