Palmitic Acid Upregulates Type I Interferon-Mediated Antiviral Response and Cholesterol Biosynthesis in Human Astrocytes

Chronic intake of a high-fat diet increases saturated fatty acids in the brain causing the progression of neurodegenerative diseases. Palmitic acid is a free fatty acid abundant in the diet that at high concentrations may penetrate the blood brain barrier and stimulate the production of pro-inflammatory cytokines, leading to inflammation in astrocytes. The use of the synthetic neurosteroid tibolone in protection against fatty acid toxicity is emerging, but its transcriptional effects on palmitic acid induced lipotoxicity remain unclear. Herein, we performed a transcriptome profiling of normal human astrocytes to investigate the molecular mechanisms by which palmitic acid causes cellular damage to astrocytes, and whether tibolone could reverse its detrimental effects. Astrocytes undergo a profound transcriptional change at 2 mM palmitic acid, affecting the expression of 739 genes, 366 upregulated and 373 downregulated. However, tibolone at 10 nM does not entirely reverse palmitic acid effects. Additionally, the protein protein interaction reveals two novel gene clustering modules. The first module involves astrocyte defense responses by upregulation of pathways associated with antiviral innate immunity, and the second is linked to lipid metabolism. Our data suggest that activation of viral response signaling pathways might be so far, the initial molecular mechanism of astrocytes in response to a lipotoxic insult by palmitic acid, triggered particularly upon increased expression levels of *IFIT2*, *IRF1*, and *XAF1*. Therefore, this novel approach using a global gene expression analysis may shed light on the pleiotropic effects of palmitic acid on astrocytes, and provide a basis for future studies addressed to elucidate these responses in neurodegenerative conditions, which is highly valuable for the design of therapeutic strategies. Normal Human Astrocytes (NHA) cell cultures were treated with Palmitic Acid, Tibolone, and Palmitic Acid + Tibolone. There are two controls: 1. DMEM, for the treatment with Tibolone, and 2. Vehicle, for the treatments with Palmitic Acid and Palmitic Acid + Tibolone. The vehicle contains 1.35% BSA and 2mM carnitine. Each of these 5 treatments have 2 technical replicates (RNA coming from the same NHA donor) and 3 biological replicates (RNA coming from different NHA donors with different sex) summing up 30 samples in total. NHA1 is from a male donor, NHA2 is from a female donor, and NHA3 is from a female donor too.