In search of genes differentially expressed between M1 (pro‐Th1 or pro‐inflammatory) and M2 (pro‐Th2 or pro‐tolerogenic) macrophages, BIC (microRNA 155 hosting gene) was found up regulated under inflammatory conditions. MicroRNAs are non coding RNAs of ~22nt in length that inhibit gene expression upon pairing to the 3’UTR (UnTranslated Region) of target mRNAs. In silico analysis predicted two pro‐Th2 targets for miR‐155: PU.1 and IL13R1. PU.1 is a transcription factor essential in myelopoiesis and dendritic cells (DCs) that favours a Th2 profiling; moreover, PU.1 had been shown to regulate the transcription of DC‐SIGN (Dendritic Cell‐ Specific ICAM‐3 Grabbing Non‐integrin 1) which is a pathogen receptor expressed in DCs controlled by Th2 stimuli. IL13R1 is the chain receptor for the Th2 cytokine IL‐13, which promotes M2 differentiation. Pro Th1 stimuli cause maturation of DCs, cells that orchestrate the immune response between Th1 and Th2 profiles; moreover, Th1 stimuli cause classical (M1) macrophages activation versus an alternative (M2) one. My hypothesis was that miR‐155 contributes to the pro‐Th1 profile by down regulating pro‐Th2 factors. MiR‐155 was found up regulated during DC maturation and both PU.1 and IL13R1 were demonstrated as direct targets of miR‐155. Employing a developed monocytic cell line which harbors a miR‐155 transgene under the control of a Tet‐On system (THP1‐155 cells), both PU.1 and IL13R1 were shown to be down regulated following miR‐155 induction in these cells. Moreover, THP1‐155 cells showed that DC‐SIGN transcription is regulated by miR‐155 levels through PU.1 targeting, and that IL‐13 signalling cascade through STAT6 transcription factor was down regulated when miR‐155 was over expressed. Using Anti miR‐155 transfections in DCs, miR‐155 was shown to modulate not only DC‐SIGN expression, but also DC pathogen binding ability. Using the same technique in macrophages, miR‐155 was shown to modulate IL13R1 and STAT6 activation, and to regulate the expression of IL‐13/STAT6 dependent genes. Therefore, miR‐155 contributes to the pro‐Th1 profile by down regulating pro‐Th2 factors, acting as a pro‐Th1/anti‐Th2 modulator in myeloid cells under inflammatory conditions
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:536300 |
| Date | January 2010 |
| Creators | Martinez-Nunez, Rocio Teresa |
| Contributors | Sanchez-Elsner, Tilman |
| Publisher | University of Southampton |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://eprints.soton.ac.uk/196569/ |
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