Abstract Body: Background: There is a growing appreciation that neutrophils demonstrate plasticity, not unlike the macrophage, and can modulate both inflammation and repair following organ injury. Neutrophils are rapidly recruited to the heart after acute myocardial infarction (MI) and participate in cardiac inflammation and remodeling. Nevertheless, mechanisms regulating neutrophil function during heart injury remain largely unknown.
Research Question/Aim: Previous work demonstrated that Yes-Associated Protein (YAP) regulates macrophage function during heart injury. However, whether YAP regulates neutrophil function in any context, including reperfused MI (I/R), remains unexplored.
Approach: We generated neutrophil-specific YAP KO mice (MRP8^Cre) and subjected them to I/R to elicit inflammation and injury. Cell-based experiments were performed using primary isolated mouse neutrophils. We utilized flow cytometry, single-cell RNAseq, and histological and biochemical assays to investigate underlying mechanisms.
Results: Neutrophils isolated from the blood and heart of WT mice subjected to I/R revealed increased YAP expression. Compared to control mice, neutrophil YAP KO hearts had decreased infarct size after 24 hours reperfusion, and better cardiac function after 2 weeks. Single-cell RNAseq of heart leukocytes indicated suppression of inflammatory, migratory, and superoxide production pathways in YAP KO neutrophils. Characterization of neutrophils by flow cytometry indicated a shift toward reparative polarization in YAP KO mice during early reperfusion. Bone marrow-derived neutrophils (BMDNs) from KO mice had attenuated inflammatory gene expression and ROS production compared to control cells. Pharmacological inhibition of YAP using verteporfin produced comparable results. Ongoing experiments are investigating how YAP modulates neutrophil inflammatory function, and will determine the therapeutic potential of targeted YAP inhibition for I/R injury.
Conclusion: These results suggest that YAP regulates neutrophil function during I/R injury in the heart and that suppression of neutrophil YAP affords cardioprotection.