Macrophage migration inhibitory factor (MIF) is a pivotal regulator of the immune response. Neutralization or genetic deletion of MIF does not completely abrogate activation responses, however, and deletion of the MIF receptor, CD74, produces a more pronounced phenotype than MIF deficiency. We hypothesized that these observations may be explained by a second MIF-like ligand, and we considered a probable candidate to be the protein encoded by the homologous, D-dopachrome tautomerase (D-DT) gene. We show that recombinant D-DT protein binds CD74 with high affinity, leading to activation of ERK1/2 MAP kinase and downstream proinflammatory pathways. Circulating D-DT levels correlate with disease severity in sepsis or malignancy, and the specific immunoneutralization of D-DT protects mice from lethal endotoxemia by reducing the expression of downstream effector cytokines. These data indicate that D-DT is a MIF-like cytokine with an overlapping spectrum of activities that are important for our understanding of MIF-dependent physiology and pathology.inflammation | lipopolysaccharide | septic shock M acrophage migration inhibitory factor (MIF) is the first cytokine activity described and a key regulatory mediator that is released upon activation of different cell types (1-3). MIF increases macrophage antimicrobial responses and it is expressed upstream of cytokines such as tumor necrosis factor (TNF)-α, IFN-γ, and IL-1β (4). MIF activates immune cells by binding to CD74, leading to the recruitment of CD44 into a signaling complex, the stimulation of nonreceptor tyrosine kinases, and initiation of the ERK1/2 MAP kinase pathway (5, 6). The chemokine receptors CXCR2 and CXCR4 also become activated by MIF via noncognate interactions that are reinforced in the presence of CD74 (7). Among mesenchymal cell types, MIF binding to cardiomyocyte CD74 stimulates the AMP-activated kinase (AMPK) cascade to mediate protection from ischemic injury (8, 9).Although MIF receptor knockout mice (CD74) phenocopy features of MIF deficiency (10-12), recent observations have led to the hypothesis that there may be a second ligand for CD74. MIF-deficient B cells, for example, are more sensitive to apoptosis than wild-type B cells, but the magnitude of this defect is twofold more pronounced in CD74-deficient cells (13). Intravital microscopy studies also have shown a more pronounced effect of antagonism of CD74 than MIF in monocyte arrest (7). Finally, anti-MIF antibodies, although highly effective in experimental studies, do not completely inhibit CD74-dependent cellular activation responses (14).We hypothesized that these observations may be explained by a second MIF-like ligand, and we considered a likely candidate to be the protein encoded by the DDT gene, D-dopachrome tautomerase (D-DT). DDT and MIF show a conserved intron-exon structure and their coding regions are highly homologous. The genes for MIF and D-DT are in close apposition to each other and to two theta-class glutathione S-transferases, suggesting that these gene clusters arose by...

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It is well known that the immune response decreases during aging, leading to a higher susceptibility to infections, cancers and autoimmune disorders. Most widely studied have been alterations in the adaptive immune response. Recently, the role of the innate immune response as a first-line defence against bacterial invasion and as a modulator of the adaptive immune response has become more widely recognized. One of the most important cell components of the innate response is neutrophils and it is therefore important to elucidate their function during aging. With aging there is an alteration of the receptor-driven functions of human neutrophils, such as superoxide anion production, chemotaxis and apoptosis. One of the alterations underlying these functional changes is a decrease in signalling elicited by specific receptors. Alterations were also found in the neutrophil membrane lipid rafts. These alterations in neutrophil functions and signal transduction that occur during aging might contribute to the significant increase in infections in old age.

Emergency colectomy reduces mortality in some patients with fulminant CDAD.

ELABELA (ELA) was recently discovered as a novel endogenous ligand of the apelin receptor (APJ), a G protein-coupled receptor. ELA signaling was demonstrated to be crucial for normal heart and vasculature development during embryogenesis. We delineate here ELA's structure-activity relationships and report the identification of analogue 3 (ELA(19-32)), a fragment of ELA that binds to APJ, activates the Gαi1 and β-arrestin-2 signaling pathways, and induces receptor internalization similarly to its parent endogenous peptide. An alanine scan performed on 3 revealed that the C-terminal residues are critical for binding to APJ and signaling. Finally, using isolated-perfused hearts and in vivo hemodynamic and echocardiographic measurements, we demonstrate that ELA and 3 both reduce arterial pressure and exert positive inotropic effects on the heart. Altogether, these results present ELA and 3 as potential therapeutic options in managing cardiovascular diseases.