Dataset Information

Derivation of ligands for the complement C3a receptor from the C-terminus of C5a.

ABSTRACT: The complement cascade is a highly sophisticated network of proteins that are well regulated and directed in response to invading pathogens or tissue injury. Complement C3a and C5a are key mediators produced by this cascade, and their dysregulation has been linked to a plethora of inflammatory and autoimmune diseases. Consequently, this has stimulated interest in the development of ligands for the receptors for these complement peptides, C3a receptor, and C5a1 (C5aR/CD88). In this study we used computational methods to design novel C5a1 receptor ligands. However, functional screening in human monocyte-derived macrophages using the xCELLigence label-free platform demonstrated altered specificity of our ligands. No agonist/antagonist activity was observed at C5a1, but we instead saw that the ligands were able to partially agonize the closely related complement receptor C3a receptor. This was verified in the presence of C3a receptor antagonist SB 290157 and in a stable cell line expressing either C5a1 or C3a receptor alone. C3a agonism has been suggested to be a potential treatment of acute neutrophil-driven traumatic pathologies, and may have great potential as a therapeutic avenue in this arena.

SUBMITTER: Halai R

PROVIDER: S-EPMC4263610 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Derivation of ligands for the complement C3a receptor from the C-terminus of C5a.

Halai Reena R Bellows-Peterson Meghan L ML Branchett Will W Smadbeck James J Kieslich Chris A CA Croker Daniel E DE Cooper Matthew A MA Morikis Dimitrios D Woodruff Trent M TM Floudas Christodoulos A CA Monk Peter N PN

European journal of pharmacology 20141030

The complement cascade is a highly sophisticated network of proteins that are well regulated and directed in response to invading pathogens or tissue injury. Complement C3a and C5a are key mediators produced by this cascade, and their dysregulation has been linked to a plethora of inflammatory and autoimmune diseases. Consequently, this has stimulated interest in the development of ligands for the receptors for these complement peptides, C3a receptor, and C5a1 (C5aR/CD88). In this study we used ...[more]

PMID: 25446428

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Project description:BackgroundHepatitis B virus (HBV) infections represent a global health problem and chronic hepatitis B (CHB) leads to liver cirrhosis and hepatocellular carcinoma. Thus, timely diagnosis of hepatitis B is crucial to ensure adequate treatment. We developed a powerful and rapid whole blood-based cytokine release assay assessing cellular immune responses to HBV antigens. IL-2 and IFNγ release in this assay depicts hepatitis B vaccination status. Of note, CHB goes along with elevated C5a concentrations in plasma. We aim at mimicking the proinflammatory microenvironment associated with HBV infection to enhance the diagnostic quality of our HBV specific cytokine release assay. We specifically investigated the potential of the complement factors C3a and C5a as costimulators and analyzed their potential effects on activation marker expression on T cells and antigen presenting cells.ResultsWhole blood from 87 healthy individuals (n = 59 hepatitis B vaccinated, n = 28 unvaccinated) was stimulated with HBV surface antigen (HBsAg) in presence or absence of C3a or C5a, respectively. Further, C3a and C5a were used in combination to investigate potential synergistic effects. IL-2 and IFNγ levels in plasma were quantified using ELISA. Complement factor C5a specifically enhances HBsAg-mediated IL-2 (690.3 ± 195.4 pg/ml vs. 789.4 ± 216.5 pg/ml) and IFNγ (146.0 ± 43.1 pg/ml vs. 336.7 ± 67.9 pg/ml) responses in whole blood. Similar cytokine levels were measured when both C3a and C5a were used. With a diagnostic specificity of 90% the IFNγ release assay reached a diagnostic sensitivity of 49.2% upon whole blood stimulation with HBsAg alone, but of 78.9% when HBsAg was combined with C3a and C5a.ConclusionsInnate signals mediated via complement pathways contribute to HBV-specific cellular immune responses. The massively improved diagnostic sensitivity of the IFNγ release assay after addition of C3a and C5a demonstrates that these effects render whole blood-based cytokine release assays even more potent as screening tools in HBV immunology and HBV vaccination studies.

Project description:Early-onset pre-eclampsia is characterized by decreased placental perfusion, new-onset hypertension, angiogenic imbalance, and endothelial dysfunction associated with excessive activation of the innate immune complement system. Although our previous studies demonstrated that inhibition of complement activation attenuates placental ischemia-induced hypertension using the rat reduced uterine perfusion pressure (RUPP) model, the important product(s) of complement activation has yet to be identified. We hypothesized that antagonism of receptors for complement activation products C3a and C5a would improve vascular function and attenuate RUPP hypertension. On gestational day (GD) 14, rats underwent sham surgery or vascular clip placement on ovarian arteries and abdominal aorta (RUPP). Rats were treated once daily with the C5a receptor antagonist (C5aRA), PMX51 (acetyl-F-[Orn-P-(D-Cha)-WR]), the C3a receptor antagonist (C3aRA), SB290157 (N(2)-[(2,2-diphenylethoxy)acetyl]-l-arginine), or vehicle from GD 14-18. Both the C3aRA and C5aRA attenuated placental ischemia-induced hypertension without affecting the decreased fetal weight or decreased concentration of free circulating vascular endothelial growth factor (VEGF) also present in this model. The C5aRA, but not the C3aRA, attenuated placental ischemia-induced increase in heart rate and impaired endothelial-dependent relaxation. The C3aRA abrogated the acute pressor response to C3a peptide injection, but it also unexpectedly attenuated the placental ischemia-induced increase in C3a, suggesting nonreceptor-mediated effects. Overall, these results indicate that both C3a and C5a are important products of complement activation that mediate the hypertension regardless of the reduction in free plasma VEGF. The mechanism by which C3a contributes to placental ischemia-induced hypertension appears to be distinct from that of C5a, and management of pregnancy-induced hypertension is likely to require a broad anti-inflammatory approach.

Dataset Information

Derivation of ligands for the complement C3a receptor from the C-terminus of C5a.

Publications

Derivation of ligands for the complement C3a receptor from the C-terminus of C5a.

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