Abstract
Abstract only Introduction: About 65% of women in their reproductive years use contraception, with combined oral contraceptives (OC) being among the most popular. OC, which contain estrogen and progestin, are linked to a higher risk of stroke, particularly in the first year of use. This study aims to explore the mechanisms and effects of OC exposure on stroke outcomes. Methods: Adult female Sprague-Dawley rats (n= 6-8/group) were randomly assigned to receive either a placebo or OC by oral gavage for 12-14 estrous cycles. The animals were divided into two cohorts following treatment. In the first cohort, brain tissue was harvested to obtain an unbiased global metabolomic profile (Metabolon Inc.) This metabolomic analysis was supplemented with western blotting and enzyme activity measurements of key altered pathways. The second cohort underwent either transient middle cerebral artery occlusion (tMCAO; 90 min) or sham surgery and was observed for 21 days. During this post-tMCAO/sham period, cognition was assessed using the Morris water maze, followed by brain collection for histopathological and immunohistochemical analysis. Results: OC exposure significantly increased infarct volume and impaired cognition in rats compared to the placebo group. Metabolomic analysis revealed significant alterations in sphingolipid metabolism, particularly an increase in sphingosine 1-phosphate (S1P) levels (p<0.05) in OC-exposed brains. A crucial enzyme for generation of S1P is Sphingosine Kinase 2 (SphK2) in the brain. Western blot analysis confirmed significant increases in SphK2 protein levels upon OC exposure. Additionally, OC exposure led to a significant decrease in sphingosine 1-phosphate lyase protein levels, responsible for S1P degradation. We also observed a notable increase in S1P receptor 3 protein levels, which plays a key role in inflammation. Therefore, microglial activation was quantified in the brain following tMCAO. Conclusion: The data indicate that OC exposure worsens ischemic outcomes by altering S1P metabolism. Future studies are needed to better understand S1P's role in OC-induced ischemic outcomes, which could help identify potential therapeutic targets.