TGFβ signalling plays an important role in IL4-induced alternative activation of microglia

Xiaolai Zhou1, Björn Spittau, Kerstin Krieglstein

  • 1Institute for Anatomy and Cell Biology, Department of Molecular Embryology, Albert-Ludwigs-University Freiburg, Albertstraße 17, Freiburg 79104, Germany.

Abstract

Insights

Transforming growth factor beta (TGFβ) enhances interleukin-4 (IL4)-induced alternative activation of microglia, revealing its crucial role in neuroinflammation and immune regulation.

Area of Science:

  • Neuroscience
  • Immunology
  • Cell Biology

Background:

  • Microglia, the central nervous system's immune cells, are implicated in neurodegenerative diseases.
  • Microglia exhibit classical (M1) and alternative (M2) activation states, similar to peripheral macrophages.
  • Transforming growth factor beta (TGFβ) is a key anti-inflammatory cytokine, primarily studied for inhibiting M1 activation, with its role in M2 activation unexplored.

Purpose of the Study:

  • To investigate the role of TGFβ in interleukin-4 (IL4)-induced alternative activation of microglia.
  • To elucidate the signaling pathways involved in TGFβ-mediated modulation of microglial alternative activation.

Main Methods:

  • Utilized BV2 and primary mouse microglia treated with IL4, TGFβ, or both.
  • Assessed alternative activation markers (Arginase1 and Chitinase 3-like 3) via quantitative RT-PCR and western blots.
  • Investigated TGFβ signaling pathways using receptor inhibitors and measured endogenous TGFβ release.

Main Results:

  • TGFβ significantly enhanced IL4-induced expression of alternative activation markers (Arg1, Ym1) in microglia.
  • This synergistic effect was dependent on TGFβ receptor signaling and partially mediated by MAPK pathways.
  • IL4 treatment induced endogenous TGFβ2 release, and TGFβ alone upregulated IL4 receptor alpha, increasing microglial sensitivity to IL4.

Conclusions:

  • TGFβ plays a novel, crucial role in promoting IL4-induced alternative activation of microglia.
  • These findings highlight TGFβ's function as an anti-inflammatory and immunoregulatory factor in microglia.
  • The study consolidates TGFβ's importance in modulating microglial immune responses within the central nervous system.

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