储存红细胞（RBC）回输不良反应（TRAE）是目前研究热点，但其发生机制尚不明确。我们在前一研究中发现，以一氧化氮（NO）生物利用率降低为特征的内皮功能障碍动物，对TRAE尤为敏感。通过建立小鼠RBC储存模型，我们初步证实游离血红蛋白（Hb）对NO的清除在TRAE发生过程中发挥了重要作用。在此基础上结合最新研究进展，本项目大胆假设，Hb对NO弥散功能的调节也参与了TRAE的发生，力图在完善Hb对NO信号调节理论的同时，系统阐明TRAE发生的确切机制。同时本项目还创新性的提出在体外直接对储存RBC进行NO负载的方法，力争在增加NO含量的同时，将RBC中的游离Hb氧化为高铁Hb，使其丧失对NO的清除能力，从而实现减少TRAE发生的目的。这些研究可以拓展对TRAE发生机制的认识，并在此基础上开发具有临床推广前景的潜在治疗方法，为增强临床用血的安全性和有效性提供理论支持和实验依据。

The putative “red blood cell (RBC) hypothermic storage lesion during ex vivo storage” is the focus of intense interest and investigation in recent years. However, the clinical significance of transfusion of “old blood” remains unclear. Recently, several meta-analysis indicate that certain pathologic conditions sensitize the recipients, including those undergoing cardiac surgery, trauma victims, and critically ill patients, to the old blood transfusion related adverse effects (TRAE). These susceptible hosts are endothelial dysfunctional with nitric oxide (NO) reduction considered to be the hallmark. This raises fundamental question regarding the actual risk associated with transfusion of stored blood: If endothelial dysfunction is expected to promote TRAE. In the previous study, we reveal that syngeneic transfusion of stored mouse RBCs induces TRAE in mice suffering endothelial dysfunction (HFD and db/db mice), whereas such response are not evident in wild-type (healthy) mice. In addition, our previous study also implicates extracellular free hemoglobin as the offending molecule. Extracellular free hemoglobin avidly scavenges NO and thus reduces NO bioavailability. Furthermore, it has recently been proved Hb also regulates NO diffusion from endothelium to smooth muscle via Hbα expressed in endothelial cells and at the myoendothelial junction. The hypothesis that will be testified in this project is that the increased free Hb after stored blood transfusion down-regulates NO signaling through scavenging NO and decreasing NO diffusion from endothelium to smooth muscles, and thus cause adverse reactions to old blood transfusion. This grant application proposes studies to investigate the underlying mechanisms of TRAE and meanwhile to explore simple methods to prevent TRAE by reducing Hb-NO interaction via treating stored blood in vitro before transfusion. Learning which patient populations and why they are at great risk of, and finding a effective method to alleviate the adverse responses to transfusion of stored blood would be a major advance allowing better utilization of blood bank resources.