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Published on: August 13, 2013
miR-155 promotes Th17 differentiation by targeting FOXP3 to aggravate inflammation in MRSA pneumonia
Keyin Tian1, Weihua Xu2, Mingxiao Chen2
1Children's Medical Center of Anhui Medical University, Department of Pediatric nephrology, Hefei 230051, Anhui, China; The Fifth Clinical College of Anhui Medical University, Hefei 230051, Anhui, China; Anhui Provincial Children's Hospital, Department of Pediatric emergency, Hefei 230051, Anhui, China.
Background:
Previous researches have clarified that miR-155 is increased in methicillin-resistant Staphylococcus aureus (MRSA) pneumonia, and modulates Th9 differentiation. Like Th9 cells, Th17 cells were also a subset of CD4+ T cells and involved in MRSA pneumonia progression. This work aimed to investigate the role and mechanism of miR-155 in Th17 differentiation.
Methods:
Bronchoalveolar lavage fluid (BALF) was collected from children with MRSA pneumonia and bronchial foreign bodies. MRSA-infected murine model was established followed by collecting BALF and lung tissues. qRT-PCR, ELISA and flow cytometry were performed to examine the mRNA expression and concentration of IL-17 and the number of Th17 cells in above samples. HE and ELISA were used to evaluate inflammatory responses in lung. Furthermore, CD4+ T cells were isolated from BALF of children for in vitro experiments. After treatments with miR-155 mimic/inhibitor, the roles of miR-155 in Th17/IL-17 regulation were determined. The downstream of miR-155 was explored by qRT-PCR, western blotting, dual luciferase reporter analysis and RIP assay.
Results:
The levels of IL-17 and the proportion of Th17 cells were increased in children with MRSA pneumonia. A similar pattern was observed in MRSA-infected mice. On the contrary, IL-17 neutralization abolished the activation of Th17/IL-17 induced by MRSA infection. Furthermore, IL-17 blockade diminished the inflammation caused by MRSA. In vitro experiments demonstrated miR-155 positively regulated IL-17 expression and Th17 differentiation. Mechanistically, FOXP3 was a direct target of miR-155. miR-155 inhibited FOXP3 level via binding between FOXP3 and Argonaute 2 (AGO2), the key component of RNA-induced silencing complex (RISC). FOXP3 overexpression reversed elevated IL-17 levels and Th17 differentiation induced by miR-155.
Conclusions:
miR-155 facilitates Th17 differentiation by reducing FOXP3 through interaction of AGO2 and FOXP3 to promote the pathogenesis of MRSA pneumonia. IL-17 blockade weakens the inflammation due to MRSA, which provides a nonantibiotic treatment strategy for MRSA pneumonia.
Insights
MicroRNA-155 (miR-155) promotes methicillin-resistant Staphylococcus aureus (MRSA) pneumonia by enhancing Th17 cell differentiation. Blocking IL-17 offers a potential nonantibiotic treatment strategy for MRSA pneumonia.
Area of Science:
- Immunology
- Molecular Biology
- Microbiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is associated with increased miR-155 levels.
- Both Th9 and Th17 cells, subsets of CD4+ T cells, are implicated in MRSA pneumonia pathogenesis.
- The specific role of miR-155 in Th17 cell differentiation requires elucidation.
Purpose of the Study:
- To investigate the role of miR-155 in Th17 cell differentiation in MRSA pneumonia.
- To elucidate the underlying molecular mechanisms by which miR-155 influences Th17 responses.
Main Methods:
- Analysis of bronchoalveolar lavage fluid (BALF) and lung tissues from children and mice with MRSA pneumonia.
- Quantitative real-time PCR (qRT-PCR), ELISA, and flow cytometry to assess IL-17 levels and Th17 cell populations.
- In vitro experiments using isolated CD4+ T cells treated with miR-155 mimics/inhibitors, followed by mechanistic studies including Western blotting and dual-luciferase reporter assays.
Main Results:
- Elevated IL-17 levels and increased Th17 cell proportions were observed in MRSA pneumonia patients and mice.
- miR-155 was found to positively regulate IL-17 expression and promote Th17 differentiation in vitro.
- FOXP3 was identified as a direct target of miR-155, with miR-155 inhibiting FOXP3 expression via the AGO2/RISC complex.
Conclusions:
- miR-155 promotes Th17 differentiation by downregulating FOXP3, thereby exacerbating MRSA pneumonia pathogenesis.
- IL-17 blockade effectively reduces MRSA-induced inflammation, suggesting a potential nonantibiotic therapeutic approach.
