The receptor for advanced glycation end products mediates lung endothelial activation by RBCs

Abstract

The receptor for advanced glycation end products (RAGE) is a multiligand pattern recognition receptor implicated in multiple disease states. Although RAGE is expressed on systemic vascular endothelium, the expression and function of RAGE on lung endothelium has not been studied. Utilizing in vitro (human) and in vivo (mouse) models, we established the presence of RAGE on lung endothelium. Because RAGE ligands can induce the expression of RAGE and stored red blood cells express the RAGE ligand N ε -carboxymethyl lysine, we investigated whether red blood cell (RBC) transfusion would augment RAGE expression on endothelium utilizing a syngeneic model of RBC transfusion. RBC transfusion not only increased lung endothelial RAGE expression but enhanced lung inflammation and endothelial activation, since lung high mobility group box 1 and vascular cell adhesion molecule 1 expression was elevated following transfusion. These effects were mediated by RAGE, since endothelial activation was absent in RBCtransfused RAGE knockout mice. Thus, RAGE is inducibly expressed on lung endothelium, and one functional consequence of RBC transfusion is increased RAGE expression and endothelial activation. receptor for advanced glycation end products; red blood cell transfusion; endothelial cell; lung inflammation; red blood cells THE RECEPTOR FOR ADVANCED glycation end products (RAGE) is widely expressed on systemic endothelium and functions as a pattern recognition receptor for multiple ligands, including advanced glycation end products (AGEs), high mobility group box 1 (HMGB1), calgranulins (s100A12 and s100B), amyloid ␤-proteins, Mac-1, phosphotidylserine, and lipopolysaccharide (10,24,26,35). AGEs, a heterogenous group of adducts formed during pathological states, hyperglycemia, and periods of increased oxidative stress, lead to increased generation of reactive oxygen species (ROS) and inflammatory cytokines following ligation of RAGE expressed on vascular endothelium (25,31,32). We have previously shown that stored red blood cells (RBCs) that express the RAGE ligand N ε -carboxymethyl lysine (N ε -CML) trigger lung endothelial ROS generation that was attenuated by soluble receptor for advanced glycation end products (sRAGE), the extracellular ligandbinding domain of the receptor that acts as a decoy by binding RAGE ligands (19). This finding supports the hypothesis that RAGE ligands on the surface of stored RBCs promote activation of lung endothelium, thus contributing to the pathogenesis of lung injury in susceptible transfusion recipients.Because RAGE is abundantly expressed on alveolar epithelium, particularly type I epithelial cells, and is utilized as a specific marker of alveolar epithelial injury, the existence of RAGE on pulmonary endothelium has come into question (9,28,30). Indeed, prior studies failed to detect RAGE in lung endothelium (9, 28). However, the complexities of RAGE biology render it a difficult molecule to study, since RAGE is known to exist in several different isoforms, subject to cleavage by proteases, ra...

Red Blood Cells Induce Necroptosis of Lung Endothelial Cells and Increase Susceptibility to Lung Inflammation

“…Naive mice were transfused with syngeneic RBCs as previously described (12). As depicted in Figure 7A, RBC transfusion led to enhanced RIP1-RIP3 interactions in murine lung.…”

“…In vivo, syngeneic RBC transfusion led to increased lung endothelial activation and elevated levels of the proinflammatory danger signal highmobility group box 1 (HMGB1) in the lung (12). HMGB1 is referred to as a classic damage-associated molecular pattern (DAMP) because intracellular HMGB1 is present in all nucleated cells and is critical in the homeostasis of most living cells, whereas extracellular HMGB1 possesses immunomodulatory capabilities.…”

“…Based on our previous findings of vascular activation and increased lung HMGB1 expression following RBC transfusion we hypothesized that RBC transfusions enhance susceptibility to lung inflammation though HMGB1 release (12). We asked whether human lung EC released HMGB1 following interaction with RBCs and examined the role of regulated necrotic death as a mechanism of HMGB1 release from lung endothelium (11).…”

Giving New Identities to Alveolar Epithelial Type I Cells

“…Although highly expressed by AT1 cells (2), it can also be found in pulmonary capillary endothelial cells (4). AGER mRNA, but not protein, can be detected in AT2 cells (5).…”

Guanidinylations of albumin decreased binding capacity of hydrophobic metabolites

“…Several post‐translational modifications have been described in recent years, for example advanced glycosylation (Mangalmurti et al . , Sun et al . ), oxidation (Hollyfield et al .…”