Palmitic acid induces Oxidative Stress, Senescence and Downregulates Glutamate Transporter Expression in Human Brainstem Astrocytes

Abstract

Glial cells have emerged as critical players in sympathoexcitation and neurogenic hypertension in recent years. Glutamate reuptake transporters display a high vulnerability to oxidative stress resulting in reduced uptake function. We have previously shown that obesity increases superoxide production and 3-nitro-tyrosine levels in the RVLM, suggesting that obesity-induced reduction in EAAT2 expression and activity might be mediated through oxidative stress. Our preliminary studies in human primary brainstem astrocytes (HBAs) also suggest that oxidative stress negatively impacts EAAT2 expression. However, what obesity-related factors induce oxidative stress in the brainstem of obese animals is not clear. In this study, we will test the role of palmitic acid on oxidative stress and astrocytic function in the brainstem. Cultured human brainstem astrocytes were treated with palmitic acid at the dose rate of 25μM for 24 hours. After the treatment period, the cells were collected and processed for real-time PCR analysis. Data was analyzed by unpaired student's t-test and a p-value less than 0.05 was considered statistically significant. Major findings from this study includes a) Palmitic acid mimicked obesity and increased lipid accumulation in brainstem astrocytes marked by significant increase in the expression lipid-droplet associated proteins, perilipin (PLIN) 1 and 2 b) We also found that the oxidative stress markers, NQO1, SOD2, and catalase were significantly higher in treatment group indicating that palmitic acid induced oxidative stress in brainstem astrocytes. c) Gene expression analysis of senescent markers revealed p21 and p53 were significantly upregulated in the treatment group. In addition, Lamin B1, a component of the nuclear envelope was significantly downregulated in the treatment group consistent with the senescence. d) Then we also observed increased gene expression levels of the senescence-associated secretory phenotype (SASP) factors, IL1α, TNFα, IL6, MCP1, and CXCL10, indicative of oxidative stress-induced senescence in brainstem astrocytes treated with palmitic acid. e) More importantly, the levels of glutamate reuptake transporters, EAAT1 and EAAT2 were significantly downregulated in the senescent brainstem astrocytes. Taken together all these results suggest that the palmitic acid induces oxidative stress, senescence and inflammation in the human brainstem astrocytes that could mediate sympathoexcitation through enhanced glutamate neurotransmission in the brainstem in obesity. National Heart, Blood and Lung Institute grant R15HL148844; American Heart Association Institutional Research Enhancement Award - 959725 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.