Abstract Body (Do not enter title and authors here): Background: Thrombotic diseases such as myocardial infarction and stroke are closely associated with immune inflammation and high prevalent in COVID-19 and sepsis. The pathologic mechanism is due to dysregulation and hyperactivation of platelet induced thrombotic inflammation and vascular occlusion. We surprisingly found elevated expression of Nrf3 (Nuclear factor erythroid 2-related factor 3) in platelets from COVID-19 patients and septic mouse. Considering that the role of Nrf3 still remains unknown, we aimed to investigate the pathological mechanisms of Nrf3 in platelet and thrombo-inflammation.

METHODS: Nrf3 global knockout mice and Nrf3 megakaryocyte/platelet-specific knockout mice were used for research. Platelet aggregation/secretion, integrin αIIbβ3 activation, spreading, clot retraction and calcium flux were measured. In vivo thrombus formation was detected in carotid thrombosis and pulmonary embolism. Lipopolysaccharide (LPS) intravenous injection was used to establish septic model and explore the effects of Nrf3 on platelet-induced thrombo-inflammation.

RESULTS: We found that Nrf3 expression was increased in inflammation-stimulated platelets and positively correlated with increased platelet activity. In vitro detection indicated that deficiency of Nrf3 attenuated platelet activation without significant effects on platelet counts and other types of peripheral blood cells. Nrf3^-/- mice showed reduced thrombus formation with little tendency to hemorrhage. Additionally, we demonstrated that loss of Nrf3 reduced pro-inflammatory chemokines content (IL-1β, TNF-α and S100A4), platelet-leukocyte complex and neutrophil extracellular traps (NETs), and further alleviated micro-thrombosis and inflammatory infiltration in sepsis-induced multi-organ injury. Meanwhile, Nrf3^-/- platelets exhibited lower ATP content, oxygen consumption rate (OCR) and extracellular acidification rate (ECAR), indicating that Nrf3 is closely involved in platelet energy metabolism.

CONCLUSION: Collectively, these results demonstrated that Nrf3 regulated platelet activity, thrombosis and platelet-induced inflammation by influencing energy metabolism, suggesting that Nrf3 could be a potential target for therapeutic intervention in patients at risk of thrombo-inflammation.