Clearance kinetics and matrix binding partners of the receptor for advanced glycation end products

Elucidating the sites and mechanisms of sRAGE action in the healthy state is vital to better understand the biological importance of the receptor for advanced glycation end products (RAGE). Previous studies in animal models of disease have demonstrated that exogenous sRAGE has an anti-inflammatory effect, which has been reasoned to arise from sequestration of pro-inflammatory ligands away from membrane-bound RAGE isoforms. We show here that sRAGE exhibits in vitro binding with high affinity and reversibly to extracellular matrix components collagen I, collagen IV, and laminin. Soluble RAGE administered intratracheally, intravenously, or intraperitoneally, does not distribute in a specific fashion to any healthy mouse tissue, suggesting against the existence of accessible sRAGE sinks and receptors in the healthy mouse. Intratracheal administration is the only effective means of delivering exogenous sRAGE to the lung, the organ in which RAGE is most highly expressed; clearance of sRAGE from lung does not differ appreciably from that of albumin. Copyright: © 2014 Milutinovic et al

Lack of the Receptor for Advanced Glycation End-Products Attenuates E. coli Pneumonia in Mice

Background: The receptor for advanced glycation end-products (RAGE) has been suggested to modulate lung injury in models of acute pulmonary inflammation. To study this further, model systems utilizing wild type and RAGE knockout (KO) mice were used to determine the role of RAGE signaling in lipopolysaccharide (LPS) and E. coli induced acute pulmonary inflammation. The effect of intraperitoneal (i.p.) and intratracheal (i.t.) administration of mouse soluble RAGE on E. coli injury was also investigated. Methodology/Principal Findings: C57BL/6 wild type and RAGE KO mice received an i.t. instillation of LPS, E. coli, or vehicle control. Some groups also received i.p. or i.t. administration of mouse soluble RAGE. After 24 hours, the role of RAGE expression on inflammation was assessed by comparing responses in wild type and RAGE KO. RAGE protein levels decreased in wild type lung homogenates after treatment with either LPS or bacteria. In addition, soluble RAGE and HMGB1 increased in the BALF after E. coli instillation. RAGE KO mice challenged with LPS had the same degree of inflammation as wild type mice. However, when challenged with E. coli, RAGE KO mice had significantly less inflammation when compared to wild type mice. Most cytokine levels were lower in the BALF of RAGE KO mice compared to wild type mice after E. coli injury, while only monocyte chemotactic protein-1, MCP-1, was lower after LPS challenge. Neither i.p. nor i.t. administration of mouse soluble RAGE attenuated the severity of E. coli injury in wild type mice. Conclusions/Significance: Lack of RAGE in the lung does not protect against LPS induced acute pulmonary inflammation, but attenuates injury following live E. coli challenge. These findings suggest that RAGE mediates responses to E. coli-associated pathogen-associated molecular pattern molecules other than LPS or other bacterial specific signaling responses. Soluble RAGE treatment had no effect on inflammation. © 2011 Ramsgaard et al

Lack of the Receptor for Advanced Glycation End- Products Attenuates E. coli Pneumonia in Mice

Abstract Background: The receptor for advanced glycation end-products (RAGE) has been suggested to modulate lung injury in models of acute pulmonary inflammation. To study this further, model systems utilizing wild type and RAGE knockout (KO) mice were used to determine the role of RAGE signaling in lipopolysaccharide (LPS) and E. coli induced acute pulmonary inflammation. The effect of intraperitoneal (i.p.) and intratracheal (i.t.) administration of mouse soluble RAGE on E. coli injury was also investigated

Kinetics of binding of extracellular matrix proteins in solution to solid-phase sRAGE.

a<p>Not determined due to undetectable specific binding.</p

Organ biodistribution of intraperitoneally-administered sRAGE or MSA in mice.

<p>Organ biodistribution of mouse sRAGE or MSA (A) 1 hour, (B) 2 hours, (C) 4 hours, and (D) 12 hours after intraperitoneal injection of ∼1 µCi of tracer, corresponding to ∼0.6–1.4 µg of radiolabeled protein. Asterisks indicate statistically significant differences.</p

Clearance of intratracheally-administered sRAGE from mouse lung occurs at the alveolar-capillary interface.

<p>Representative light micrographs/autoradiographs recorded at 20× magnification of sections of lung from mice given mouse sRAGE (or MSA, shown for comparison) i.t. and sacrificed at the indicated time points thereafter. Lung from untreated mice serves as a control for background radiation.</p

sRAGE and MSA used in biodistribution and clearance studies are very pure.

<p>(A) SDS-PAGE separation and Coomassie Brilliant Blue staining of ∼2.5 µg of MSA or mouse sRAGE preparations used for radiolabeling. (B) SDS-PAGE separation and gel autoradiography of ¹²⁵I-labeled MSA and mouse sRAGE.</p

Organ biodistribution of intratracheally-administered sRAGE or MSA in mice.

<p>Organ biodistribution of mouse sRAGE or MSA (A) 1 hour, (B) 2 hours, (C) 4 hours, and (D) 12 hours after intratracheal instillation of ∼1 µCi of tracer, corresponding to ∼0.6–1.4 µg of radiolabeled protein. Asterisks indicate statistically significant differences.</p