Cytokine Signaling Protein 3 Deficiency in Myeloid Cells Promotes Retinal Degeneration and Angiogenesis through Arginase-1 Up-Regulation in Experimental Autoimmune Uveoretinitis.

The suppressor of cytokine signaling protein 3 (SOCS3) critically controls immune cell activation, although its role in macrophage polarization and function remains controversial. Using experimental autoimmune uveoretinitis (EAU) as a model, we show that inflammation-mediated retinal degeneration is exaggerated and retinal angiogenesis is accelerated in mice with SOCS3 deficiency in myeloid cells (LysMCre/+SOCS3fl/fl). At the acute stage of EAU, the population of infiltrating neutrophils was increased and the population of macrophages decreased in LysMCre/+SOCS3fl/fl mice compared with that in wild-type (WT) mice. Real-time RT-PCR showed that the expression of tumor necrosis factor-α, IL-1ß, interferon-γ, granulocyte-macrophage colony-stimulating factor, and arginase-1 was significantly higher in the LysMCre/+SOCS3fl/fl EAU retina in contrast to the WT EAU retina. The percentage of arginase-1+ infiltrating cells was significantly higher in the LysMCre/+SOCS3fl/fl EAU retina than that in the WT EAU retina. In addition, bone marrow-derived macrophages and neutrophils from the LysMCre/+SOCS3fl/fl mice express significantly higher levels of chemokine (C-C motif) ligand 2 and arginase-1 compared with those from WT mice. Inhibition of arginase using an l-arginine analog amino-2-borono-6-hexanoic suppressed inflammation-induced retinal angiogenesis without affecting the severity of inflammation. Our results suggest that SOCS3 critically controls the phenotype and function of macrophages and neutrophils under inflammatory conditions and loss of SOCS3 promotes the angiogenic phenotype of the cells through up-regulation of arginase-1.

Antagonising Wnt/ß-catenin signalling ameliorates lens-capsulotomy-induced retinal degeneration in a mouse model of diabetes.

AIMS/HYPOTHESIS: Cataract surgery in diabetic individuals worsens pre-existing retinopathy and triggers the development of diabetic ocular complications, although the underlying cellular and molecular pathophysiology remains elusive. We hypothesise that lens surgery may exaggerate pre-existing retinal inflammation in diabetes, which may accelerate neurovascular degeneration in diabetic eyes. METHODS: Male heterozygous Ins2Akita mice (3 months of age) and C57BL/6 J age-matched siblings received either lens capsulotomy (to mimic human cataract surgery) or corneal incision (sham surgery) in the right eye. At different days post surgery, inflammation in anterior/posterior ocular tissues was assessed by immunohistochemistry and proinflammatory gene expression in the retina by quantitative PCR (qPCR). Degenerative changes in the retina were evaluated by electroretinography, in vivo examination of retinal thickness (using spectral domain optical coherence tomography [SD-OCT]) and morphometric analysis of retinal neurons. The therapeutic benefit of neutralising Wnt/ß-catenin signalling following lens capsulotomy was evaluated by intravitreal administration of monoclonal antibody against the co-receptor low-density lipoprotein receptor-related protein 6 (LRP6) (Mab2F1; 5 µg/µl in each eye). RESULTS: Lens capsulotomy triggered the early onset of retinal neurodegeneration in Ins2Akita mice, evidenced by abnormal scotopic a- and b-wave responses, reduced retinal thickness and degeneration of outer/inner retinal neurons. Diabetic Ins2Akita mice also had a higher number of infiltrating ionised calcium-binding adapter molecule 1 (IBA1)/CD68+ cells in the anterior/posterior ocular tissues and increased retinal expression of inflammatory mediators (chemokine [C-C motif] ligand 2 [CCL2] and IL-1ß). The expression of ß-catenin was significantly increased in the inner nuclear layer, ganglion cells and infiltrating immune cells in Ins2Akita mice receiving capsulotomy. Neutralisation of Wnt/ß-catenin signalling by Mab2F1 ameliorated ocular inflammation and prevented capsulotomy-induced retinal degeneration in the Ins2Akita mouse model of diabetes. CONCLUSIONS/INTERPRETATION: Targeting the canonical Wnt/ß-catenin signalling pathway may provide a novel approach for the postoperative management of diabetic individuals needing cataract surgery.

Cyclic adenosine monophosphate-response element-binding protein mediates the proangiogenic or proinflammatory activity of gremlin.

OBJECTIVE: Angiogenesis and inflammation are closely related processes. Gremlin is a novel noncanonical vascular endothelial growth factor receptor-2 (VEGFR2) ligand that induces a proangiogenic response in endothelial cells (ECs). Here, we investigated the role of the cyclic adenosine monophosphate-response element (CRE)-binding protein (CREB) in mediating the proinflammatory and proangiogenic responses of ECs to gremlin. APPROACH AND RESULTS: Gremlin induces a proinflammatory response in ECs, leading to reactive oxygen species and cyclic adenosine monophosphate production and the upregulation of proinflammatory molecules involved in leukocyte extravasation, including chemokine (C-C motif) ligand-2 (Ccl2) and Ccl7, chemokine (C-X-C motif) ligand-1 (Cxcl1), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1). Accordingly, gremlin induces the VEGFR2-dependent phosphorylation, nuclear translocation, and transactivating activity of CREB in ECs. CREB activation mediates the early phases of the angiogenic response to gremlin, including stimulation of EC motility and permeability, and leads to monocyte/macrophage adhesion to ECs and their extravasation. All these effects are inhibited by EC transfection with a dominant-negative CREB mutant or with a CREB-binding protein-CREB interaction inhibitor that competes for CREB/CRE binding. Also, both recombinant gremlin and gremlin-expressing tumor cells induce proinflammatory/proangiogenic responses in vivo that are suppressed by the anti-inflammatory drug hydrocortisone. Similar effects were induced by the canonical VEGFR2 ligand VEGF-A165. CONCLUSIONS: Together, the results underline the tight cross-talk between angiogenesis and inflammation and demonstrate a crucial role of CREB activation in the modulation of the VEGFR2-mediated proinflammatory/proangiogenic response of ECs to gremlin.

Hypoxia-induced responses by endothelial colony-forming cells are modulated by placental growth factor.

BACKGROUND: Endothelial colony-forming cells (ECFCs), also termed late outgrowth endothelial cells, are a well-defined circulating endothelial progenitor cell type with an established role in vascular repair. ECFCs have clear potential for cell therapy to treat ischaemic disease, although the precise mechanism(s) underlying their response to hypoxia remains ill-defined. METHODS: In this study, we isolated ECFCs from umbilical cord blood and cultured them on collagen. We defined the response of ECFCs to 1% O2 exposure at acute and chronic time points. RESULTS: In response to low oxygen, changes in ECFC cell shape, proliferation, size and cytoskeleton phenotype were detected. An increase in the number of senescent ECFCs also occurred as a result of long-term culture in 1% O2. Low oxygen exposure altered ECFC migration and tube formation in Matrigel®. Increases in angiogenic factors secreted from ECFCs exposed to hypoxia were also detected, in particular, after treatment with placental growth factor (PlGF). Exposure of cells to agents that stabilise hypoxia-inducible factors such as dimethyloxalylglycine (DMOG) also increased PlGF levels. Conditioned medium from both hypoxia-treated and DMOG-treated cells inhibited ECFC tube formation. This effect was reversed by the addition of PlGF neutralising antibody to the conditioned medium, confirming the direct role of PlGF in this effect. CONCLUSIONS: This study deepens our understanding of the response of ECFCs to hypoxia and also identifies a novel and important role for PlGF in regulating the vasculogenic potential of ECFCs.

Sustained intraocular VEGF neutralization results in retinal neurodegeneration in the Ins2(Akita) diabetic mouse.

Current therapies that target vascular endothelial growth factor (VEGF) have become a mainstream therapy for the management of diabetic macular oedema. The treatment involves monthly repeated intravitreal injections of VEGF inhibitors. VEGF is an important growth factor for many retinal cells, including different types of neurons. In this study, we investigated the adverse effect of multiple intravitreal anti-VEGF injections (200 ng/µl/eye anti-mouse VEGF164, once every 2 weeks totalling 5-6 injections) to retinal neurons in Ins2(Akita) diabetic mice. Funduscopic examination revealed the development of cotton wool spot-like lesions in anti-VEGF treated Ins2(Akita) mice after 5 injections. Histological investigation showed focal swellings of retinal nerve fibres with neurofilament disruption. Furthermore, anti-VEGF-treated Ins2(Akita) mice exhibited impaired electroretinographic responses, characterized by reduced scotopic a- and b-wave and oscillatory potentials. Immunofluorescent staining revealed impairment of photoreceptors, disruptions of synaptic structures and loss of amacrine and retinal ganglion cells in anti-VEGF treated Ins2(Akita) mice. Anti-VEGF-treated WT mice also presented mild amacrine and ganglion cell death, but no overt abnormalities in photoreceptors and synaptic structures. At the vascular level, exacerbated albumin leakage was observed in anti-VEGF injected diabetic mice. Our results suggest that sustained intraocular VEGF neutralization induces retinal neurodegeneration and vascular damage in the diabetic eye.

Bone morphogenetic proteins and their antagonists: current and emerging clinical uses.

Bone morphogenetic proteins (BMPs) are members of the TGFß superfamily of secreted cysteine knot proteins that includes TGFß1, nodal, activins and inhibins. BMPs were first discovered by Urist in the 1960s when he showed that implantation of demineralized bone into intramuscular tissue of rabbits induced bone and cartilage formation. Since this seminal discovery, BMPs have also been shown to play key roles in several other biological processes, including limb, kidney, skin, hair and neuronal development, as well as maintaining vascular homeostasis. The multifunctional effects of BMPs make them attractive targets for the treatment of several pathologies, including bone disorders, kidney and lung fibrosis, and cancer. This review will summarize current knowledge on the BMP signalling pathway and critically evaluate the potential of recombinant BMPs as pharmacological agents for the treatment of bone repair and tissue fibrosis in patients.

Under the right conditions: protecting podocytes from diabetes-induced damage.

Hyperglycemia-induced damage to the glomerular podocyte is thought to be a critical early event in diabetic nephropathy. Interventions that prevent podocyte damage or loss have been shown to have potential for the treatment of diabetic nephropathy. New data show that conditioned medium from adipocyte-derived mesenchymal stem cells has the potential to protect podocytes from high-glucose-induced damage. Furthermore, epidermal growth factor may be the critical ingredient mediating this effect. These data suggest that components of the conditioned medium of mesenchymal stem cells, in addition to the cells themselves, may have potential for the treatment of diseases such as diabetic nephropathy.

The gastrointestinal peptide obestatin induces vascular relaxation via specific activation of endothelium-dependent NO signalling.

BACKGROUND AND PURPOSE: Obestatin is a recently discovered gastrointestinal peptide with established metabolic actions, which is linked to diabetes and may exert cardiovascular benefits. Here we aimed to investigate the specific effects of obestatin on vascular relaxation. EXPERIMENTAL APPROACH: Cumulative relaxation responses to obestatin peptides were assessed in rat isolated aorta and mesenteric artery (n≥ 8) in the presence and absence of selective inhibitors. Complementary studies were performed in cultured bovine aortic endothelial cells (BAEC). KEY RESULTS: Obestatin peptides elicited concentration-dependent relaxation in both aorta and mesenteric artery. Responses to full-length obestatin(1-23) were greater than those to obestatin(1-10) and obestatin(11-23). Obestatin(1-23)-induced relaxation was attenuated by endothelial denudation, l-NAME (NOS inhibitor), high extracellular K(+) , GDP-ß-S (G-protein inhibitor), MDL-12,330A (adenylate cyclase inhibitor), wortmannin (PI3K inhibitor), KN-93 (CaMKII inhibitor), ODQ (guanylate cyclase inhibitor) and iberiotoxin (BK(Ca) blocker), suggesting that it is mediated by an endothelium-dependent NO signalling cascade involving an adenylate cyclase-linked GPCR, PI3K/PKB, Ca(2+) -dependent eNOS activation, soluble guanylate cyclase and modulation of vascular smooth muscle K(+) . Supporting data from BAEC indicated that nitrite production, intracellular Ca(2+) and PKB phosphorylation were increased after exposure to obestatin(1-23). Relaxations to obestatin(1-23) were unaltered by inhibitors of candidate endothelium-derived hyperpolarizing factors (EDHFs) and combined SK(Ca) /IK(Ca) blockade, suggesting that EDHF-mediated pathways were not involved. CONCLUSIONS AND IMPLICATIONS: Obestatin produces significant vascular relaxation via specific activation of endothelium-dependent NO signalling. These actions may be important in normal regulation of vascular function and are clearly relevant to diabetes, a condition characterized by endothelial dysfunction and cardiovascular complications.