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BACKGROUND: Repeated ischemia/reperfusion in a tissue/organ remote from the heart (remote ischemic conditioning, RIC) protects against injury from sustained myocardial ischemia/reperfusion (I/R). Platelets are considered as mediators/targets of RIC´s protection. We have recently reported that infusion of washed platelets, taken from healthy volunteers after RIC, reduced infarct size (IS) in isolated rat hearts (FASEB Journal 2021; 35; S1; DOI: 10.1096/fasebj.2021.35.S1.03444). Anti-platelet drugs are potential confounders of RIC. AIM: To study the impact of anti-platelet drugs, the cyclooxygenase inhibitor aspirin and the P2Y12 inhibitor ticagrelor, on the platelet-mediated transfer of cardioprotection. METHODS: We included 18 healthy volunteers. As a contemporary control, volunteers were subjected to RIC through 3 x 5 min blood pressure cuff inflation at 200 mmHg on the left upper arm/ 5 min deflation. After at least 2 weeks, these volunteers were again subjected to RIC 3 hours after pretreatment with oral aspirin (500-1000 mg) and again at least another 2 weeks later 2 hours after pretreatment with oral ticagrelor (180 mg). Venous blood samples were taken before RIC and 60 min after RIC, respectively. Washed platelets were prepared using apyrase, prostaglandin E1 and citrated Tyrode-buffer. The platelet count was adjusted to 2.5 x 105 platelets/µL. The functionality of washed platelets was tested in response to thrombin (1U/ml), aggregation measured with turbodimetric light transmission aggregometry and expressed as the increase in light transmission in percent of control. Platelet preparations with an aggregation

Purpose: The role of platelets during myocardial ischemia/reperfusion (I/R) is ambivalent. They contribute to injury but also to cardioprotection. Repeated blood flow restriction and reperfusion in a tissue/organ remote from the heart (remote ischemic conditioning, RIC) reduce myocardial I/R injury and attenuate platelet activation. Whether or not platelets mediate RIC’s cardioprotective signal is currently unclear. Methods and Results: Venous blood from healthy volunteers (without or with pretreatment of 500/1000 mg aspirin or 180 mg ticagrelor orally, 2–3 h before the study, n = 18 each) was collected before and after RIC (3 × 5 min blood pressure cuff inflation at 200 mmHg on the left upper arm/5 min deflation). Washed platelets were isolated. Platelet-poor plasma was used to prepare plasma-dialysates. Platelets (25 × 103/µL) or plasma-dialysates (1:10) prepared before and after RIC from untreated versus aspirin- or ticagrelor-pretreated volunteers, respectively, were infused into isolated buffer-perfused rat hearts. Hearts were subjected to global 30 min/120 min I/R. Infarct size was stained. Infarct size was less with infusion of platelets/plasma-dialysate after RIC (18 ± 7%/23 ± 9% of ventricular mass) than with platelets/plasma-dialysate before RIC (34 ± 7%/33 ± 8%). Aspirin pretreatment abrogated the transfer of RIC’s cardioprotection by platelets (after/before RIC, 34 ± 7%/33 ± 7%) but only attenuated that by plasma-dialysate (after/before RIC, 26 ± 8%/32 ± 5%). Ticagrelor pretreatment induced an in vivo formation of cardioprotective factor(s) per se (platelets/plasma-dialysate before RIC, 26 ± 7%/26 ± 7%) but did not impact on RIC’s cardioprotection by platelets/plasma-dialysate (20 ± 7%/21 ± 5%). Conclusion: Platelets serve as carriers for RIC’s cardioprotective signal through an aspirin-sensitive and thus cyclooxygenase-dependent mechanism. The P2Y12 inhibitor ticagrelor per se induces a humoral cardioprotective signal. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).