Circulating Extracellular Vesicle-Mediated Immune Activation After Resuscitation From Cardiac Arrest in Swine

Objective: Systemic inflammation is a well-established contributor to morbidity and mortality in patients that are initially resuscitated from sudden cardiac arrest (SCA). However, our mechanistic understanding of immune activation in this context remains limited, impeding the development of targeted anti-inflammatory treatments. To address this knowledge gap, we tested the hypothesis that post-resuscitation immune cell activation is mediated, at least in part, by circulating extracellular vesicles (EVs). Methods: Swine (n=3) were subjected to 10 minutes of electrically-induced SCA followed by CPR with defibrillation and epinephrine (0.015 mg/kg iv) to achieve return of spontaneous circulation (ROSC). Blood samples were collected before SCA and 4-hours post-ROSC for isolation of plasma EVs from clarified plasma using 100kD filters, which were subsequently quantified by Nano-particle Tracking Analysis (ZetaView). Naïve PBMCs from healthy swine were cultured with basal media (negative control), lipopolysaccharide (LPS; positive control), or EVs isolated from pre-SCA or post ROSC plasma that were stained with lipophilic dye (DiD) to facilitate assessment of EV uptake (n=3 per group). After 24 hours in culture, PBMC activation was assessed via surface marker expression (flow cytometry) and inflammatory cytokine release (ELISA). Results: Compared with exposure to pre-SCA EVs and basal media, PBMCs exposed to post-ROSC EVs exhibited a significant shift toward an inflammatory phenotype, with enrichment of inflammatory dendritic cells (CD172+CD16+), inflammatory granulocytes (CD172+CD163-), and inflammatory macrophages (CD14+CD163+) in both DiD+ and DiD- cell populations (all p<0.05 vs. pre-SCA EVs). Although TNF-α, IFN-α, and IFN-γ were not detected after EV co-culture, a near-significant increase in IL-1β release was observed in PBMCs exposed to post-ROSC EVs vs. pre-SCA EVs (5.72±2.4 vs. 2.21±0.7 pg/mL; p=0.068). Conclusion: Our findings suggest that circulating plasma EVs may contribute to immune cell activation following systemic ischemia/reperfusion injury associated with resuscitation from SCA. Further studies to delineate mechanisms underlying EV-mediated pro-inflammatory shifts in immune cell phenotype and potentiation of IL-1β release may reveal novel therapeutic targets to mitigate post-resuscitation inflammation and improve patient outcomes following SCA. Supported by funding from the NIH and US Department of Veteran's Affairs. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.