Objective-Sepsis is a major cause of death for intensive care patients. High concentrations of inflammatory cytokines are characteristic of severe systemic inflammation and activated monocytes are their predominant cellular source. To identify targets for antiinflammatory intervention, we investigated the response of human macrophages to inflammatory and antiinflammatory mediators. Methods and Results-We profiled gene expression in human macrophages exposed to lipopolysaccharide (LPS) and interferon (IFN)-␥ in the presence or absence of recombinant activated protein C (APC) or IL-10 and identified Wnt5A as one of the transcripts most highly induced by LPS/IFN-␥ and suppressed by APC and IL-10. We confirmed regulation of Wnt5A protein in macrophages and detected it in sera and bone marrow macrophages of patients with severe sepsis. We established that a functional Wnt5A/frizzled-5/CaMKII signaling pathway was essential for macrophage inflammatory activation. To prove the essential contribution of Wnt5A we measured inflammatory cytokines after stimulation with Wnt5A, silenced Wnt5A by siRNA, and blocked receptor binding with soluble Frizzled-related peptide-1 (sFRP1). Key Words: geneexpression Ⅲ macrophages Ⅲ activated protein C S epsis is a suspected or proven infection with a systemic inflammatory response. In severe sepsis, organ dysfunction also occurs and it is associated with a high mortality and morbidity. Severe sepsis still causes about 9.3% of all deaths in the USA. 1,2
Conclusion-Wnt5A is critically involved in inflammatory macrophage
See accompanying article on page 400During sepsis, the extent of plasma protein C depletion correlates with the severity of the outcome. 3 In animal studies 4 and clinical trials APC prevented death from severe sepsis or septic shock. 5 Although this beneficial effect of APC is mostly ascribed to its anticoagulant properties, antiinflammatory effects of APC have also been proposed. 6 The direct modulation of inflammation by APC has recently been described in gene expression profiling studies with human endothelial cells. 7,8 Recently, recombinant human APC has been introduced as a therapeutic agent for treatment of patients with severe sepsis because of its unique anticoagulant and antiinflammatory properties; however, the exact mechanism of antiinflammatory action is still unknown. 9 Macrophages play a central role in inflammation by responding to and releasing of numerous inflammatory cytokines and chemokines, leading to severe systemic inflammation and septic shock. However, the knowledge of antiinflammatory interactions on the level of monocytes/macrophages is scant. Therefore, we decided to expand our investigations on antiinflammatory effects of APC on this cellular system. In the present study, we were using a whole genome expression analysis approach, to define novel targets of APC in an in vitro model of inflammatory macrophage activation. Using probes obtained from human macrophages stimulated by INF-␥ (IFN-␥) and endotoxin (LPS), we consistently found Wnt5A to ...
Release of hemoglobin (Hb) into the circulation is a central pathophysiologic event that contributes to morbidity and mortality in chronic hemolytic anemias and severe malaria. These toxicities arise from Hb-mediated vasoactivity, possibly due to NO scavenging and localized tissue oxidative processes. Currently, there is no established treatment that targets circulating extracellular Hb. Here, we assessed the role of haptoglobin (Hp), the primary scavenger of Hb in the circulation, in limiting the toxicity of cell-free Hb infusion. Using a canine model, we found that glucocorticoid stimulation of endogenous Hp synthesis prevented Hb-induced hemodynamic responses. Furthermore, guinea pigs administered exogenous Hp displayed decreased Hbinduced hypertension and oxidative toxicity to extravascular environments, such as the proximal tubules of the kidney. The ability of Hp to both attenuate hypertensive responses during Hb exposure and prevent peroxidative toxicity in extravascular compartments was dependent on Hb-Hp complex formation, which likely acts through sequestration of Hb rather than modulation of its NO-and O 2 -binding characteristics. Our data therefore suggest that therapies involving supplementation of endogenous Hb scavengers may be able to treat complications of acute and chronic hemolysis, as well as counter the adverse effects associated with Hb-based oxygen therapeutics.
Wnt proteins are members of the highly conserved wingless family of proteins responsible for cell differentiation and development and for neoplastic and degenerative processes. Recently, Toll-like receptor-mediated Wnt signaling was found to be associated with innate immunity in Drosophila. Upregulation of Wnt5A in human macrophages upon microbial challenge indicated a similar mechanism. Toll-like receptor-mediated Wnt5A expression is a key process for sustained inflammatory macrophage activation through autocrine and paracrine signaling. Downregulation of Wnt5A expression and subsequent attenuation of inflammatory macrophage responses by activated protein C supports the link between inflammation and coagulation, another highly conserved biologic system. Direct evidence for the relevance of Wnt5A in severe systemic inflammation is provided by the finding of higher Wnt5A levels in patients with sepsis than in healthy individuals. The fact that Wnt5A signaling can be modulated by anti-inflammatory mediators makes this effector molecule an attractive target for therapeutic intervention in inflammatory diseases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.