Characterisation of the Fpr2 null mouse

PhDA novel Fpr2-/- mouse colony was used to explore the biology of Fpr2, a GPCR related to the human FPR2/ALX receptor that recognises lipoxin A4 (LXA4) annexin A1 (AnxA1) and serum amyloid A (SAA). Southern blotting, PCR and radio-ligand binding confirmed receptor deletion in the mouse Fpr2-/- colony. A GFP target/reporter strategy was employed in generating this novel transgenic to monitor promoter activity in living cells. This study revealed a propensity of Fpr2 for granulocytes, as well as a distinct role in macrophage (Mφ) maturation. Characterisation of Fpr2-/- Mφ revealed selective ERK phosphorylation triggered by the AnxA1-derived peptide Ac2-26, W peptide and Compound 43 (C43). Despite this Fpr-dependent signalling cascade via ERK, it was not a functional prognostic for cell migration in vitro or in vivo. Formyl peptide (fMLP) and serum amyloid A (SAA) chemotactic action was attenuated in Fpr2-/- Mφ, as well as the pro-phagocytic effects of Ac2-26 and LXA4. There was no observable naïve phenotype associated with Fpr2 depletion. To investigate the patho-physiology of Fpr2, acute and chronic inflammatory models were investigated in vivo to dissect different aspects of the receptor during disease progression. Notably Fpr2-/- mice exhibited stimulus specific discrepancies in inflammatory response. An acute IL-1β-induced air pouch model 6 revealed predominantly anti-migratory pharmacology of Fpr2 ligands, with a notable exception of SAA, discovered to be anti-migratory in the absence of Fpr2. Analysis of the full time-course of the zymosan peritonitis pointed to a subtle role for Fpr2 in neutrophil and monocyte migration as well as Mφ maturation. Of interest, exudate levels of SAA were augmented in Fpr2-/- mice revealing complex regulatory receptor/ligand circuits active during on-going inflammatory reactions. Finally, Fpr2-/- mice displayed pronounced arthritic responses upon treatment with the K/BxN arthrogenic serum, in comparison to their wild type controls. We conclude that Fpr2 can serve varied regulatory functions during the host response to inflammatory insult

The endothelial transcription factor ERG promotes vascular stability and growth through Wnt/β-catenin signaling.

Blood vessel stability is essential for embryonic development; in the adult, many diseases are associated with loss of vascular integrity. The ETS transcription factor ERG drives expression of VE-cadherin and controls junctional integrity. We show that constitutive endothelial deletion of ERG (Erg(cEC-KO)) in mice causes embryonic lethality with vascular defects. Inducible endothelial deletion of ERG (Erg(iEC-KO)) results in defective physiological and pathological angiogenesis in the postnatal retina and tumors, with decreased vascular stability. ERG controls the Wnt/β-catenin pathway by promoting β-catenin stability, through signals mediated by VE-cadherin and the Wnt receptor Frizzled-4. Wnt signaling is decreased in ERG-deficient endothelial cells; activation of Wnt signaling with lithium chloride, which stabilizes β-catenin levels, corrects vascular defects in Erg(cEC-KO) embryos. Finally, overexpression of ERG in vivo reduces permeability and increases stability of VEGF-induced blood vessels. These data demonstrate that ERG is an essential regulator of angiogenesis and vascular stability through Wnt signaling.This work was funded by grants from the British Heart Foundation (PG/09/096 and RG/11/17/29256). A.V.S. is a recipient of a National Lung and Heart Institute Foundation Studentship. I.M.A. is a recipient of a DOC-fFORTE fellowship of the Austrian Academy of Sciences at the London Research Institute.This paper was published by Cell Press in Developmental Cell (GM Birdsey, AV Shah, N Dufton, LE Reynolds, LO Almagro, Y Yang, IM Aspalter, ST Khan, JC Mason, E Dejana, B Göttgens, K Hodivala-Dilke, Gerhardt, RH Adams, AM Randi, Developmental Cell 2015, 32, 82-96

Up-Regulation of Annexin-A1 and Lipoxin A4 in Individuals with Ulcerative Colitis May Promote Mucosal Homeostasis

PubMed ID: 22723974This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference

Anti-inflammatory role of the murine formyl-peptide receptor 2:ligand-specific effects on leukocyte responses and experimental inflammation

The human formyl-peptide receptor (FPR)-2 is a G protein-coupled receptor that transduces signals from lipoxin A(4), annexin A1, and serum amyloid A (SAA) to regulate inflammation. In this study, we report the creation of a novel mouse colony in which the murine FprL1 FPR2 homologue, Fpr2, has been deleted and describe its use to explore the biology of this receptor. Deletion of murine fpr2 was verified by Southern blot analysis and PCR, and the functional absence of the G protein-coupled receptor was confirmed by radioligand binding assays. In vitro, Fpr2(−/−) macrophages had a diminished response to formyl-Met-Leu-Phe itself and did not respond to SAA-induced chemotaxis. ERK phosphorylation triggered by SAA was unchanged, but that induced by the annexin A1-derived peptide Ac2–26 or other Fpr2 ligands, such as W-peptide and compound 43, was attenuated markedly. In vivo, the antimigratory properties of compound 43, lipoxin A(4), annexin A1, and dexamethasone were reduced notably in Fpr2(−/−) mice compared with those in wild-type littermates. In contrast, SAA stimulated neutrophil recruitment, but the promigratory effect was lost following Fpr2 deletion. Inflammation was more marked in Fpr2(−/−) mice, with a pronounced increase in cell adherence and emigration in the mesenteric microcirculation after an ischemia–reperfusion insult and an augmented acute response to carrageenan-induced paw edema, compared with that in wild-type controls. Finally, Fpr2(−/−) mice exhibited higher sensitivity to arthrogenic serum and were completely unable to resolve this chronic pathology. We conclude that Fpr2 is an anti-inflammatory receptor that serves varied regulatory functions during the host defense response. These data support the development of Fpr2 agonists as novel anti-inflammatory therapeutics

Endothelial dimethylarginine dimethylaminohydrolase 1 is an important regulator of angiogenesis but does not regulate vascular reactivity or hemodynamic homeostasis

Background—Asymmetrical dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthesis and a risk factor for cardiovascular disease. Dimethylarginine dimethylaminohydrolase (DDAH) enzymes are responsible for ADMA breakdown. It has been reported that endothelial DDAH1 accounts for the majority of ADMA metabolism. However, we and others have shown strong DDAH1 expression in a range of nonendothelial cell types, suggesting that the endothelium is not the only site of metabolism. We have developed a new endothelium-specific DDAH1 knockout mouse (DDAH1En−/−) to investigate the significance of endothelial ADMA in cardiovascular homeostasis. Methods and Results—DDAH1 deletion in the DDAH1En−/− mouse was mediated by Tie-2 driven Cre expression. DDAH1 deletion was confirmed through immunocytochemistry, whereas Western blotting showed that DDAH1 remained in the kidney and liver, confirming expression in nonendothelial cells. Plasma ADMA was unchanged in DDAH1En−/− mice, and cultured aortas released amounts of ADMA to similar to controls. Consistent with these observations, vasoreactivity ex vivo and hemodynamics in vivo were unaltered in DDAH1En−/− mice. In contrast, we observed significantly impaired angiogenic responses both ex vivo and in vivo. Conclusions—We demonstrate that endothelial DDAH1 is not a critical determinant of plasma ADMA, vascular reactivity, or hemodynamic homeostasis. DDAH1 is widely expressed in a range of vascular and nonvascular cell types; therefore, the additive effect of DDAH1 expression in multiple organ systems determines plasma ADMA concentrations. Endothelial deletion of DDAH1 profoundly impairs the angiogenic capacity of endothelial cells, indicating that intracellular ADMA is a critical determinant of endothelial cell response