IMPAIRED SIGNALING OF NF-κB AND NRF2 IN CX3CR1-DEFICIENT MICROGLIA: IMPLICATIONS IN TAUOPATHIES.

Abstract

TAU protein aggregation is the main characteristic of neurodegenerative diseases known as tauopathies. Low-grade chronic inflammation is also another hallmark that indicates crosstalk between damaged neurons and glial cells. We have demonstrated that neurons overexpressing TAUP301L release CX3CL1, which activates anti-inflammatory NRF2 signalling in microglial cells in vitro and in vivo. However, the potential role of CX3CR1 in the context of tauopathies and its implication in neuroinflammation are poorly described. In this work we show that CX3CL1 activates the pro-inflammatory pathway as an early response mediated by the transcription factor NF-{kappa}B through the activation of mitogen-and stress-activated protein kinase-1 (MSK-1). At a functional level, CX3CR1-deficient microglia show decreased expression of NRF2, impaired cell migration and deficiency of phagocytosis. The relevance of these findings is evident in a tauopathy model, where the treatment with an inducer of NRF2, sulforaphane, is able to modulate astrogliosis but not microgliosis. These findings suggest that CX3CR1/NRF2 axis is essential in microglial activation associated with tauopathies and that polymorphisms have to be taken into account to development of therapeutic strategies