Abstract
Byline: Shahil H Patel, Neurology, Univ of Miami Miller Sch of Medicine, Miami, FL; Isabel Saul; Kunjan R Dave; Miguel A Perez-Pinzon; Ami P Raval Significance: Smoking-derived nicotine (N) is known to synergistically magnify the risk and severity of cerebral ischemia in females. Most importantly, smoking is the one preventable risk factor and giving up smoking reduces the risk for cerebral ischemia. However, how long the harmful effects of N on the brain persist after women stop smoking is unknown. In a laboratory study using an animal model of cerebral ischemia, we demonstrated that N alters brain energy metabolism and thus exacerbates ischemic brain damage. Therefore, the current study aims to investigate how long after N withdrawal (NW) N toxicity on brain energy metabolism persists and its impact on stroke outcomes in female rats. Methods: Female Sprague-Dawley rats (n=8/group) were randomly exposed to either saline or N (4.5 mg/kg) for 16-21 days after which point, they were withdrawn from N exposure and able to recover for 0, 15, or 30 days. These rats were then randomly assigned to either have their cortical tissue collected for global metabolomic (Metabolon Inc) and Western blot analysis or undergo a sham surgery or transient middle-cerebral artery occlusion (tMCAO; 90 min). Post-stroke cognition was tested with contextual fear conditioning at month following tMCAO, subsequently the brains were collected for infarct quantification. Results: Analysis of the metabolomics data revealed an increase in carbohydrate metabolites in the 30-day NW group when compared to the N-exposed group, suggesting persistence of N toxicity in the brain. Furthermore, fear conditioning data revealed a significantly lower freezing time in all NW groups when compared to the saline group implying that spatial memory deficits persist even after 30 days of NW. Lastly, the observed infarct volume was 26%(p<0.05), 25%(p<0.05), and 16%(p<0.05) higher in the 0, 15, and 30 day NW groups respectively, when compared to the saline group. Conclusion: Even after 30 days of NW, N-induced global metabolomic changes in the brain persist and may be responsible for increased ischemic brain damage as well as cognitive deficits in female rats.
