The shedding-derived soluble receptor for advanced glycation endproducts sustains inflammation during acute Pseudomonas aeruginosa lung infection.

BACKGROUND: The membrane-bound isoform of the receptor for advanced glycation end products (FL-RAGE) is primarily expressed by alveolar epithelial cells and undergoes shedding by the protease ADAM10, giving rise to soluble cleaved RAGE (cRAGE). RAGE has been associated with the pathogenesis of several acute and chronic lung disorders. Whether the proteolysis of FL-RAGE is altered by a given inflammatory stimulus is unknown. Pseudomonas aeruginosa causes nosocomial infections in hospitalized patients and is the major pathogen associated with chronic lung diseases. METHODS: P. aeruginosa was injected in Rage-/- and wild-type mice and the impact on RAGE expression and shedding, levels of inflammation and bacterial growth was determined. RESULTS: Acute P. aeruginosa lung infection in mice induces a reduction of the active form of ADAM10, which determines an increase of FL-RAGE expression on alveolar cells and a concomitant decrease of pulmonary cRAGE levels. This was associated with massive recruitment of leukocytes and release of pro-inflammatory factors, tissue damage and relocation of cRAGE in the alveolar and bronchial cavities. The administration of sRAGE worsened bacterial burden and neutrophils infiltration. RAGE genetic deficiency reduced the susceptibility to P. aeruginosa infection, mitigating leukocyte recruitment, inflammatory molecules production, and bacterial growth. CONCLUSIONS: These data are the first to suggest that inhibition of FL-RAGE shedding, by affecting the FL-RAGE/cRAGE levels, is a novel mechanism for controlling inflammation to acute P. aeruginosa pneumonia. sRAGE in the alveolar space sustains inflammation in this setting. GENERAL SIGNIFICANCE: RAGE shedding may determine the progression of inflammatory lung diseases.

The receptor for advanced glycation end-products (RAGE) is only present in mammals, and belongs to a family of cell adhesion molecules (CAMs).

The human receptor for advanced glycation endproducts (RAGE) is a multiligand cell surface protein belonging to the immunoglobulin superfamily, and is involved in inflammatory and immune responses. Most importantly, RAGE is considered a receptor for HMGB1 and several S100 proteins, which are Damage-Associated Molecular Pattern molecules (DAMPs) released during tissue damage. In this study we show that the Ager gene coding for RAGE first appeared in mammals, and is closely related to other genes coding for cell adhesion molecules (CAMs) such as ALCAM, BCAM and MCAM that appeared earlier during metazoan evolution. RAGE is expressed at very low levels in most cells, but when expressed at high levels, it mediates cell adhesion to extracellular matrix components and to other cells through homophilic interactions. Our results suggest that RAGE evolved from a family of CAMs, and might still act as an adhesion molecule, in particular in the lung where it is highly expressed or under pathological conditions characterized by an increase of its protein levels.

Ypt32p and Mlc1p bind within the vesicle binding region of the class V myosin Myo2p globular tail domain.

Myosin V is an actin-based motor essential for a variety of cellular processes including skin pigmentation, cell separation and synaptic transmission. Myosin V transports organelles, vesicles and mRNA by binding, directly or indirectly, to cargo-bound receptors via its C-terminal globular tail domain (GTD). We have used the budding yeast myosin V Myo2p to shed light on the mechanism of how Myo2p interacts with post-Golgi carriers. We show that the Rab/Ypt protein Ypt32p, which associates with membranes of the trans-Golgi network, secretory vesicles and endosomes and is related to the mammalian Rab11, interacts with the Myo2p GTD within a region previously identified as the 'vesicle binding region'. Furthermore, we show that the essential myosin light chain 1 (Mlc1p), required for vesicle delivery at the mother-bud neck during cytokinesis, binds to the Myo2p GTD in a region overlapping that of Ypt32p. Our data are consistent with a role of Ypt32p and Mlc1p in regulating the interaction of post-Golgi carriers with Myo2p subdomain II.

Anorexia nervosa is characterized by increased adiponectin plasma levels and reduced nonoxidative glucose metabolism.

The aim of the present study was to examine the effects of anorexia nervosa (AN) on adipocytokines (leptin and adiponectin) plasma concentrations and insulin-stimulated glucose disposal in adolescent and young adult women. Adiponectin and leptin plasma levels, along with insulin-stimulated glucose disposal (as measured by the euglycemic-hyperinsulinemic glucose clamp) and oxidative and nonoxidative glucose metabolism (as measured by indirect calorimetry during the last 60 min of the insulin clamp), were measured in 11 anorectic patients and 26 normal-weight healthy female controls. Leptin levels were significantly lower in AN patients, according to the reduced body mass index and their respective fat mass. On the contrary, adiponectin plasma levels were significantly higher in AN patients than in control women. Likewise, insulin-stimulated glucose disposal and nonoxidative glucose metabolism were significantly lower in AN patients. In conclusion, our study shows that young women affected by AN have higher adiponectin plasma levels than healthy female controls of similar age, despite the presence of an impairment of insulin-stimulated glucose disposal, with a prevalent failure of nonoxidative glucose metabolism. Taken together, these data suggest that the reduction of fat mass may play the major role in the control of adiponectin release, with respect to changes in insulin sensitivity.