No abstract

Our findings indicate that product storage time and WBC burden increase the number and strength of adhesion of RBCs to vascular endothelium. These results may lead to greater understanding of the interaction of transfused RBCs with recipient endothelium and the biologic consequences of this adherence.

Oxysterols are oxygenated derivatives of cholesterol. They have been shown to influence a variety of biological functions including sterol metabolism, lipid trafficking, and apoptosis. Recently, 12 human OSBP-related genes have been identified. In this study, we have identified a family of 12 oxysterol-binding protein (OSBP)-related proteins (ORPs) in the mouse. A high level of amino acid identity (88-97%) was determined between mouse and human ORPs, indicating a very high degree of evolutionary conservation. All proteins identified contained the conserved OSBP amino acid sequence signature motif "EQVSHHPP," and most contained a pleckstrin homology (PH) domain. Using RT-PCR, each mouse ORP gene was found to exhibit a unique tissue distribution with many showing high expression in testicular, brain, and heart tissues. Interestingly, the tissue distribution of ORP-4 and ORP-10 were the most selective within the family. Expression of the various ORP genes was also investigated, specifically in highly purified populations of hemopoietic precursor cells defined by the lin(-) c-kit(+) Sca-1(+) (LKS(+)) and lin(-) c-kit(+) Sca-1(-) (LKS(-)) immunophenotype. Most ORP genes were expressed in both LKS(+) and LKS(-) populations, although ORP-4 appeared to be more highly expressed in the primitive, stem-cell enriched LKS(+) population, whereas ORP-10 was more highly expressed by maturing LKS(-) cells. The identification of a family of ORP proteins in the mouse, the frequently preferred animal model for in vivo studies, should further our understanding of the function of these proteins and their interactions with each other.

Red blood cells (RBCs) that have been stored prior to transfusion show increased adherence to vascular endothelium in vitro, which suggests a potential for stored blood transfusion to impede blood flow in some patients. Transfusion is often required in patients with sepsis or inflammation; however, whether activation of endothelium affects stored RBC-endothelial cell (EC) interactions is unknown. We investigated whether storage time and leukocyte content of RBC products influences the adhesion of RBCs to activated ECs. RBCs from nonleukocytereduced (S-RBCs), buffy-coat-poor (BCP-RBCs), and leukocyte-filtered (LF-RBCs) products and cultured EC layers were pretreated with endotoxin, tumor necrosis factor-a (TNF-a), or medium alone prior to perfusion of the RBCs across the EC layer in a continuous flow microchamber. After a single day of RBC storage, the number of adherent RBCs was increased in the endotoxin and TNF-a pretreated groups compared to the unactivated-control group. These differences were statistically significant for S-RBCs and LF-RBC products (P < 0.05). In contrast, there was no significant difference in RBC adherence to activated and unactivated endothelium at other time-points of RBC product storage. The strength of adhesion of stored RBCs from S-RBC products to activated ECs was not altered following treatment; however, endotoxin significantly increased the adhesive strength of LF-RBCs to endothelium. These results demonstrate that while fresh RBCs show increased adhesion to activated endothelium, storage of RBCs did not promote increased adhesion to activated endothelium. However, inflammatory conditions promote stronger adhesion of stored RBCs to ECs, which may contribute to impaired tissue perfusion in some transfusion recipients. Am. J. Hematol. 82:439-445, 2007. V V C 2006 Wiley-Liss, Inc.

Proteomics provides a valuable approach to examine storage-related effects on RBCs. Such analytical approaches may help to elucidate the mechanisms involved in the RBC storage lesion and provide insights into the biologic consequences of transfusion of stored RBC products.