ARYL HYDROCARBON RECEPTOR CYTOPLASMIC RETENTION BY P27^KIP1 IN SENESCENT ASTROCYTES

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor involved in diverse physiological processes, including neuroinflammation, dysbiosis, cellular senescence, and other processes related to aging, neurodegeneration, and cancer. We investigated the mechanisms underlying AhR dysfunction in senescent human astrocytes, specifically identifying the cyclin-dependent kinase inhibitor p27^Kip1 as a critical AhR mediator.
Using the SVPg12 human astrocyte cell line—induced into senescence via oxidative stress—we analyzed AhR localization and expression through confocal immunofluorescence. Changes in protein expression levels, transcriptional activity, and related molecular mechanisms were quantified by Western blot, RT-qPCR, and ELISAs. Protein interactions were assessed by immunoprecipitation and in silico simulations. AhR activation was also evaluated in senescent astrocytes by exposure to indole-3-propionic acid (IPA).
The results show an increase of up to 66% and cytoplasmic localization of AhR in senescent astrocytes, followed by a decrease of up to 57% in CYP1A1 expression, its target gene. The interaction of AhR with p27^{^Kip1} in the cytoplasm was also observed experimentally and in silico studies. Activation of AhR by IPA promoted its nuclear translocation and restored its transcriptional activity.
Our findings suggest that p27^Kip1-mediated cytoplasmic retention is a primary driver of AhR dysfunction during astrocyte senescence. Furthermore, we suggest that some ligands may compete with p27^Kip1 for its transactivation site, thereby making this pathway a therapeutic target to mitigate the pro-inflammatory and degenerative effects of astrocyte aging.