Abstract
Abstract only Introduction: The rise in popularity of nicotine-containing electronic cigarettes (ECs) globally necessitates a deeper understanding of their effects on stroke outcomes. This study investigates the influence of EC exposure on post-ischemic inflammation. Methods: Adult Sprague-Dawley rats of both sexes were randomly assigned to either air or EC vapor exposure (5% nicotine Juul pods) for 16 nights, followed by transient middle cerebral artery occlusion (tMCAO; 90 minutes) or sham surgery. Post-surgery, animals were divided into two cohorts. In the first cohort, cortical brain tissue was collected 24 hours after tMCAO or sham surgery for Western blot analysis of inflammasome proteins, including Caspase-1, Interleukin-1β (IL-1β), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and gasdermin-D (GSDMD). The second cohort was sacrificed 21 days post-tMCAO for immunohistochemical analysis of microglial marker ionized calcium-binding adapter molecule-1 (Iba-1). De-ramified microglia were quantified across three serial coronal sections (10 μm) using the optical fractionator probe in StereoInvestigator software, with a counting frame of 100x100 μm and approximately 40 sampling sites per section. Microglial morphology and Sholl analysis were performed by capturing three cortical images per slide, each containing at least three microglia, and across three slides per subject, resulting in 18 images for peri-infarct and contralateral areas. Analysis was conducted using ImageJ software. Results: Western blot analysis revealed a significant increase in Caspase-1 and ASC protein levels in the ipsilateral cortex of EC-exposed female rats compared to males after tMCAO (p<0.05). Quantification of Iba-1 indicated an increase in de-ramified microglia in the cortex of EC-exposed female rats as compared to air-exposed after tMCAO, potentially exacerbating post-stroke infarction. Microglial morphology analysis showed increased cell soma size and decreased branch length in EC-exposed female rats. Sholl analysis demonstrated reduced microglial complexity in EC-exposed group as compared to air-exposed after tMCAO, with a smaller area under the curve and fewer peak intersections in the cortex. Conclusion: EC exposure exacerbates stroke-induced inflammation and cognitive deficits in female rats. Future research should explore whether EC withdrawal mitigates ischemic severity and determine the necessary duration of withdrawal for potential recovery.