Oxidative Stress‐Induced Senescence Alters Glutamate Transporter Expression in Human Brainstem Astrocytes

Oxidative stress in the rostral ventrolateral medulla (RVLM), a key brainstem region for sympathetic cardiovascular control, has been implicated in the pathogenesis of sympathetic nervous system overactivity in obesity. Previous studies from our lab have shown that increased oxidative stress is associated with DNA damage and induction of cellular senescence in the brainstem of obese mice. Neurons are post‐mitotic and do not undergo senescence. On the other hand, glial cells especially astrocytes have been reported to undergo senescence in aging and neurodegenerative diseases. In the brainstem, astrocytes play a critical role in regulating excitatory neurotransmission through extracellular glutamate reuptake mediated by astrocytic glutamate transporters (EAAT1 and EAAT2). We hypothesized that oxidative stress induces senescence and affects glutamate transporter expression in brainstem astrocytes. To address this hypothesis, we established a cell culture system to investigate the molecular changes associated with oxidative stress‐induced senescence in human brainstem astrocytes. To mimic oxidative stress observed in high fat diet‐induced obesity, we treated cultured human brainstem astrocytes with hydrogen peroxide (H 2 O 2 ) at a dose of 300μM for 2 hrs. Senescence was assessed in the cells after 5 days by SA‐beta gal staining and using gene expression analysis of senescence markers at the end of 7 days. Data was analyzed by unpaired student's t‐test and a p‐value less than 0.05 was considered statistically significant. H 2 O 2 treatment reduced cell count and increased SA‐beta gal activity in human brainstem astrocytes. Further, we also observed increased gene expression levels of cell cycle inhibitor p21 and senescence‐associated secretory phenotype (SASP) factors including MCP1, CXCL1, IL8, CXCL10 and MMP3, suggesting oxidative stress induces senescence in human brainstem astrocytes. More importantly, senescent brainstem astrocytes had significant downregulation of glutamate reuptake transporters, EAAT1 and EAAT2. This suggests that senescent astrocytes could mediate sympathoexcitation through enhanced glutamate neurotransmission in the brainstem in obesity. Future in‐vivo studies will investigate the mechanism behind senescence‐induced alterations in glia‐neuron interaction in obesity mediated sympathoexcitation. Support or Funding Information NIH‐HL148844 and RED account funds