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AP-1 transcription factors roles in the control of macrophage polarization

Subject Area Immunology
Parasitology and Biology of Tropical Infectious Disease Pathogens
Rheumatology
Term from 2017 to 2021
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 387043890
 
Final Report Year 2022

Final Report Abstract

Macrophages play pivotal roles in the innate and adaptive immune system. On one side, they are essential for the uptake, killing and degradation of pathogens and for the processing and presentation of antigens. On the other side, they are crucial for the termination of inflammatory processes and the restoration of tissue homeostasis. To fulfil all these functions, Mφ can express a large spectrum of activation statuses ranging from classically activated Mφ (M1 Mφ) to the alternatively activated Mφ (M2 Mφ). While substantial information on the role of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) exist in Mφ functions, we have uncovered new roles of AP-1 transcription factor in this context. We have discovered an important role of Fra-1 for the functional reprogramming of macrophages. Analyses of the K/BxN arthritis mouse model and of tissue sections of patients with active or inactive RA revealed an inverse correlation between Fra-1 and Arg1. Fra-1 directly suppressed Arg1 gene transcription and thereby altered macrophage responses, which impeded the resolution of inflammation. Moreover, we could also show that FRA-1 and lipocalin 2 (cn2) were positively correlated in response to LPS, both in tolerant murine and human macrophage in vitro. Using ChIP-seq and ChIP-qPCR, FRA-1 was shown to bind Lcn2 promoter, especially in the tolerant state. Finally, in vivo septic model using consecutive injection of LPS showed a decreased resolution as well as an increased inflammation in FRA-1 depleted conditions, likely dependent on the low level of Lcn 2 in these mice. Collectively, our results indicate that FRA-1 transcription factor is involved in myeloid cell tolerant responses by mediating the functional reprogramming of Lcn2 transcription is sepsis responses.

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