Investigation of the phenotypic and metabolic profile of human astrocytes conditioned with stress stimuli

Astrocytes provide essential metabolic support to neurons by regulating the supply of energy substrates, maintaining ion balance, and modulating neurotransmitter levels; however, under conditions of metabolic stress, their dysfunction can contribute to neurodegeneration by shifting from a neuroprotective to a neurotoxic phenotype. This study investigates the effects of stress factors applied on astrocytes and their relationship with Aryl hydrocarbon Receptor (AhR) signaling, which is known to mediate cellular responses to environmental toxins and stressors. Immortalized human astrocytes were treated for 24 hours with various agents and doses: TNF-α 10,100 ng/mL, LPS 100 ng/mL, TGF-β1 2,5,10 ng/mL, AhR agonisti 6-Formylindolo[3,2-b] carbazole/FICZ 100,1000 nM; AhR-antagonisti 1,5 µM Stem Regenin-1 /SR1. Metabolome analyses of the supernatants (conditioned medium) were performed using GC-MS. RT-qPCR was used to analyze seventeen genes involved in neuroprotective and neurotoxic astrocyte responses and AhR-signaling. Increased expression of inflammatory genes was observed in the TNF-α and LPS groups and decreased expression in TGF-β1 group. Significant changes in the expression of both neurotoxic and neuroprotective-specific genes were noted in all groups. Metabolome analysis revealed higher ornithine levels and lower level of energy metabolites in the TNF-α, LPS, SR1, and low-dose TGF-β1 groups suggesting ornithine as a potential therapeutic target in neurodegeneration. Together with these findings, AhR agonist FICZ- and antagonist SR1- induced alterations in expression of the astrocyte A1 and A2 genes suggested the presence of an intermediate phase in astrocytes. Keywords: Astrocyte, stress, Neurodegeneration, neurotoxic/neuroprotective phenotypes, AhR-signaling This work was supported by the HU-BAP (Grant no: TYL-2022-20617), and partially by the TUBITAK (Grant no: 220S759)