Vascular endothelial cell growth factor (VEGF) was originally described as a potent vascular permeability factor (VPF) that importantly contributes to vascular pathobiology. The signaling pathways that underlie VEGF/VPF-induced permeability are not well defined. Furthermore, endogenous vascular peptides that regulate this important VPF function are currently unknown. We report here that VPF significantly enhances permeability in aortic endothelial cells via a linked signaling pathway, sequentially involving Src, ERK, JNK, and phosphatidylinositol 3-kinase/AKT. This leads to the serine/threonine phosphorylation and redistribution of actin and the tight junction (TJ) proteins, zona occludens-1 and occludin, and the loss of the endothelial cell barrier architecture. Atrial natriuretic peptide (ANP) inhibited VPF signaling, TJ protein phosphorylation and localization, and VPF-induced permeability. This involved both guanylate cyclase and natriuretic peptide clearance receptors. In vivo, transgenic mice that overexpress ANP showed significantly less VPF-induced kinase activation and vascular permeability compared with non-transgenic littermates. Thus, ANP acts as an anti-permeability factor by inhibiting the signaling functions of VPF that we define here and by preserving the endothelial cell TJ functional morphology.
"Even more, beyond the direct physiological mild permeability-increasing (volume-regulating) effects on quiescent endothelial cells, ANP seems to exert the opposite, namely barrier-enhancing effects on an inflammation-activated endothelium in the systemic circulation . In cultured HUVEC ANP prevented barrier disruption by inflammatory agents acting through very different types of receptors and cellular pathways, such as VEGF (Pedram et al., 2002), TNF-a (Kiemer et al., 2002) or histamine (Fürst et al., 2008). At the molecular level, ANP pretreatment attenuated the TNF-a-induced expression of adhesion molecules and monocyte chemoattractant protein-1 by inhibiting NF-kB activation and p38 mitogen-activated protein kinase signalling (Kiemer et al., 2002). "
[Show abstract][Hide abstract] ABSTRACT: The cardiac hormone atrial natriuretic peptide (ANP) is critically involved in the maintenance of arterial blood pressure and intravascular volume homeostasis. Its cGMP-producing GC-A receptor is densely expressed in the microvascular endothelium of the lung and systemic circulation, but the functional relevance is controversial. Some studies reported that ANP stimulates endothelial cell permeability, whereas others described that the peptide attenuates endothelial barrier dysfunction provoked by inflammatory agents such as thrombin or histamine. Many studies in vitro addressed the effects of ANP on endothelial proliferation and migration. Again, both pro- and anti-angiogenic properties were described. To unravel the role of the endothelial actions of ANP in vivo, we inactivated the murine GC-A gene selectively in endothelial cells by homologous loxP/Cre-mediated recombination. Our studies in these mice indicate that ANP, via endothelial GC-A, increases endothelial albumin permeability in the microcirculation of the skin and skeletal muscle. This effect is critically involved in the endocrine hypovolaemic, hypotensive actions of the cardiac hormone. On the other hand the homologous GC-A-activating B-type NP (BNP), which is produced by cardiac myocytes and many other cell types in response to stressors such as hypoxia, possibly exerts more paracrine than endocrine actions. For instance, within the ischaemic skeletal muscle BNP released from activated satellite cells can improve the regeneration of neighbouring endothelia. This review will focus on recent advancements in our understanding of endothelial NP/GC-A signalling in the pulmonary versus systemic circulation. It will discuss possible mechanisms accounting for the discrepant observations made for the endothelial actions of this hormone-receptor system and distinguish between (patho)physiological and pharmacological actions. Lastly it will emphasize the potential therapeutical implications derived from the actions of NPs on endothelial permeability and regeneration.
British Journal of Pharmacology 01/2012; 166(2):522-31. DOI:10.1111/j.1476-5381.2012.01827.x · 4.84 Impact Factor
"ANP is present in the normal circulation at low levels (0.1–0.3 ng ml −1 , i.e. < 0.1 nM). When vascular volume is expanded, ANP is released from specialized cells in the heart at concentrations that approach 1 ng ml −1 (approx 0.3 nM (Pedram et al. 2002; Schreier et al. 2008)). Infusion of ANP at rates to achieve close to this level in the plasma produce an increase in albumin clearance in a range of organs, particularly skin, muscle and the GI tract of both rats and mice (Tucker et al. 1992; Renkin & Tucker, 1998; Sabrane et al. 2005). "
[Show abstract][Hide abstract] ABSTRACT: Natriuretic peptides (such as atrial natriuretic peptide, ANP) are normally present at very low levels in the blood and are part of physiological systems that control blood volume. During diseases such as heart failure and sepsis, circulating levels of ANP increase, leading to an increase in blood vessel permeability and loss of blood fluid volume to the tissues. Other studies show that some inflammatory responses are strongly blocked by increased intracellular cAMP. Here we tested whether rolipram, an inhibitor of the degradation of cAMP, could counteract the movement of protein and fluid out of the blood that is induced by ANP. We found that rolipram almost completely blocked the ANP-induced loss of blood volume. Stabilizing the endothelial barrier by controlling cAMP levels to offset ANP-induced increases in vascular permeability may be part of a strategy to maintain plasma volume in disease states with elevated natriuretic peptides.
Abstract Inhibition of phosphodiesterase 4 (PDE4) to increase endothelial cAMP and stabilize the endothelial barrier attenuates acute inflammatory increases in vascular permeability. We extended this approach to attenuate physiological increases in vascular permeability in response to atrial natriuretic peptide (ANP), which acts with the kidney to regulate plasma volume. We measured blood-to-tissue albumin clearance and changes in plasma volume in isoflurane-anaesthetized mice (C57BL/6J) pre-treated with rolipram (8 mg kg−1 i.p., 30 min). Rolipram significantly reduced albumin permeability, measured using a dual-label fluorescence method, in skin and skeletal muscle compared with ANP alone (500 ng kg−1 min−1). Skin and muscle tissue accounted for 70% of the reduction in whole body albumin clearance taking into account albumin clearance in gastrointestinal (GI) tissue, heart and kidney. The action of ANP and rolipram to modify albumin clearances in duodenum and jejunum could be accounted for by local increases in vascular perfusion to increase surface area for exchange. ANP increased haematocrit from 40.6% to 46.8%, corresponding to an average loss of 22% plasma fluid volume (227 μl), and this was almost completely reversed with rolipram. Renal water excretion accounted for less than 30% of plasma fluid loss indicating that reduced albumin permeability and reduced filtration into vasodilated GI tissue were the predominant actions of PDE4 inhibition. Similar fluid retention was measured in mice with endothelial-restricted deletion of the guanylyl cyclase-A receptor for ANP. Stabilizing the endothelial barrier to offset ANP-induced increases in vascular permeability may be part of a strategy to maintain plasma volume.
The Journal of Physiology 01/2011; 589(Pt 2):341-53. DOI:10.1113/jphysiol.2010.199588 · 5.04 Impact Factor
"Attenuation of Rho pathway as vascular barrier protective mechanism triggered by ANP has been previously tested in the aseptic model of thrombin-induced EC hyper-permeability (Birukova et al., 2008b; Klinger et al., 2006). ANP also inhibited VEGF-induced signaling and attenuated EC permeability in part by preserving the endothelial cell tight junction functional morphology (Pedram et al., 2002). Mechanistic analysis revealed that ANP stimulated Rac GTPase via PKA-and Epac-Rap1/Tiam1/Vav2-dependent signaling cascades (Birukova et al., 2008b). "
[Show abstract][Hide abstract] ABSTRACT: We have previously reported protective effects of atrial natriuretic peptide (ANP) against endothelial cell (EC) permeability induced by thrombin via suppression of Rho GTPase pathway of barrier dysfunction by protein kinase A and Epac-Rap1-Tiam1-Rac signaling cascades. This study tested effects of ANP on EC barrier dysfunction induced by inflammatory mediators lipopolysaccharide (LPS) and TNFalpha and linked them with activation of mitogen-activated protein kinase (MAPK) and NFkappaB signaling cascades known to promote EC hyperpermeability in the models of lung inflammation and sepsis. LPS and TNFalpha increased permeability in human pulmonary EC monitored by measurements of transendothelial electrical resistance, and caused disruption of EC monolayer integrity monitored by immunofluorescence staining for adherens junction marker protein VE-cadherin. Both disruptive effects were markedly attenuated by ANP. Both LPS and TNFalpha caused sustained activation of p38 and ERK1/2 MAP kinases, increased phosphorylation and degradation of negative regulator of NFkappaB signaling IkBalpha, and increased Rho-kinase mediated phosphorylation of myosin phosphatase MYPT1 leading to accumulation of phosphorylated myosin light chains. Consistent with protective effects on EC permeability and monolayer integrity, ANP dramatically attenuated activation of inflammatory signaling by LPS and TNFalpha in pulmonary EC. These results strongly suggest inhibitory effects of ANP on the LPS and TNFalpha induced inflammatory signaling as additional mechanism of EC barrier preservation in the models of acute lung injury and sepsis.
Microvascular Research 11/2009; 79(1):56-62. DOI:10.1016/j.mvr.2009.11.006 · 2.13 Impact Factor
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