Abstract DP318: Stroke-Induced Pulmonary Dysfunction Emerges from Redox Collapse and Temporal Immune Cell Redistribution

Ischemic stroke triggers a systemic inflammatory response that extends beyond the central nervous system, impacting peripheral organs. The lungs are particularly vulnerable to secondary injury following stroke, yet the underlying mechanisms remain incompletely defined. We hypothesized that ischemic stroke disrupts pulmonary function through time-dependent immune cell redistribution and loss of vascular barrier integrity mirroring changes that occur in the CNS. Adult male C57BL/6 mice underwent 60-minute middle cerebral artery occlusion (MCAo; n = 5) or SHAM surgery (n = 5), followed by 1- or 3-day reperfusion, and were compared to naïve controls (n = 4). Lung function and vascular integrity were assessed via pulmonary mechanics (FlexiVent), bronchoalveolar lavage (BALF), and Western blotting. A subset (SHAM: n = 3; MCAo: n = 4) underwent flow cytometry and imaging mass cytometry (IMC) of lung, brain, and spleen to evaluate immune responses. At 3 days post-MCAo, mice exhibited significantly decreased lung compliance and increased airway elastance and resistance compared to SHAM, despite preserved alveolar architecture. These physiological impairments were accompanied by elevated levels of 4-HNE adducts and VCAM-1 expression in lung tissue, indicating oxidative stress and endothelial activation. BALF analysis revealed increased total protein and cellularity, along with reduced claudin-5 expression and IgG extravasation, consistent with pulmonary barrier dysfunction. Imaging mass cytometry (IMC) showed that by day 3, inflammatory marker expression in the lung was similar between MCAo and SHAM. However, at day 1, MCAo lungs demonstrated markedly reduced expression of CD45, CD44, CD11b, Ly6G, Granzyme B, and iNOS relative to both naïve and SHAM controls, suggesting early immune cell egress. Flow cytometry corroborated these findings, revealing increased splenic neutrophils and cerebral macrophages at day 1 post-MCAo, supporting a model of peripheral immune cell redistribution following stroke. These findings suggest that MCAo is associated with impaired pulmonary barrier function and mechanics, correlating with redox imbalance and temporal immune cell redistribution. The early depletion of lung-resident immune effectors likely reflects systemic immunologic reprioritization, rendering the lung transiently vulnerable to secondary insults. This defines a post-stroke window of pulmonary susceptibility with implications for infection risk and therapeutic targeting.