Sildenafil-Induced Revascularization of Rat Hindlimb Involves Arteriogenesis through PI3K/AKT and eNOS Activation.

Hypoxia and inflammation play a major role in revascularization following ischemia. Sildenafil inhibits phosphodiesterase-5, increases intracellular cGMP and induces revascularization through a pathway which remains incompletely understood. Thus, we investigated the effect of sildenafil on post-ischemic revascularization. The left femoral artery was ligated in control and sildenafil-treated (25 mg/kg per day) rats. Vascular density was evaluated and expressed as the left/right leg (L/R) ratio. In control rats, L/R ratio was 33 ± 2% and 54 ± 9%, at 7- and 21-days post-ligation, respectively, and was significantly increased in sildenafil-treated rats to 47 ± 4% and 128 ± 11%, respectively. A neutralizing anti-VEGF antibody significantly decreased vascular density (by 0.48-fold) in control without effect in sildenafil-treated animals. Blood flow and arteriolar density followed the same pattern. In the ischemic leg, HIF-1α and VEGF expression levels increased in control, but not in sildenafil-treated rats, suggesting that sildenafil did not induce angiogenesis. PI3-kinase, Akt and eNOS increased after 7 days, with down-regulation after 21 days. Sildenafil induced outward remodeling or arteriogenesis in mesenteric resistance arteries in association with eNOS protein activation. We conclude that sildenafil treatment increased tissue blood flow and arteriogenesis independently of VEGF, but in association with PI3-kinase, Akt and eNOS activation.

Topical delivery of mitogen-activated protein kinase inhibitor binimetinib prevents the development of cutaneous neurofibromas in neurofibromatosis type 1 mutant mice.

Cutaneous neurofibromas (cNFs) are a hallmark of patients with the neurofibromatosis type 1 (NF1) genetic disorder. These benign nerve sheath tumors, which can amount to thousands, develop from puberty onward, often cause pain and are considered by patients to be the primary burden of the disease. Mutations of NF1, encoding a negative regulator of the RAS signaling pathway, in the Schwann cell (SCs) lineage are considered to be at the origin of cNFs. The mechanisms governing cNFs development are poorly understood, and therapeutics to reduce cNFs are missing, mainly due to the lack of appropriate animal models. To address this, we designed the Nf1-KO mouse model that develops cNFs. Using this model, we found that cNFs development is a singular event and goes through 3 successive stages: initiation, progression, and stabilization characterized by changes in the proliferative and MAPK activities of tumor SCs. We found that skin trauma accelerated the development of cNFs and further used this model to explore the efficacy of the MEK inhibitor binimetinib to cure these tumors. We showed that while topically delivered binimetinib has a selective and minor effect on mature cNFs, the same drug prevents their development over long periods.

Protease-activated receptor-1 antagonist F 16618 reduces arterial restenosis by down-regulation of tumor necrosis factor α and matrix metalloproteinase 7 expression, migration, and proliferation of vascular smooth muscle cells.

Wound healing after angioplasty or stenting is associated with increased production of thrombin and the activation of protease-activated receptor 1 (PAR1). The aim of the present study was to examine the effects of a new selective PAR1 antagonist, 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)-penta-1,3-dienyl]-benzonitrile (F 16618), in restenosis and vascular smooth muscle cell (SMC) proliferation and migration using both in vivo and in vitro approaches. Daily oral administration of F 16618 inhibited the restenosis induced by balloon angioplasty on rat carotid artery in a dose-dependent manner. Furthermore, single intravenous administration of F 16618 during the angioplasty procedure was sufficient to protect the carotid artery against restenosis. In vitro, F 16618 inhibited the growth of human aortic SMCs in a concentration-dependent manner with maximal effects at 10 µM. At that concentration, F 16618 also prevented thrombin-mediated SMC migration. In vivo, oral and intravenous F 16618 treatments reduced by 30 and 50% the expression of the inflammatory cytokine tumor necrosis factor α (TNFα) 24 h after angioplasty. However, only acute intravenous administration prevented the induction of matrix metalloproteinase 7 expression. In contrast, F 16618 treatments had no effect on early SMC de-differentiation and transcription of monocyte chemoattractant protein-1 and interleukin-6 and late re-endothelialization of injured arteries. Furthermore, F 16618 compensated for the carotid endothelium loss by inhibiting PAR1-mediated contraction. Altogether, these data demonstrate that PAR1 antagonists such as F 16618 are a highly effective treatment of restenosis after vascular injury, by inhibition of TNFα, matrix metalloproteinase 7, and SMC migration and proliferation in addition to an antithrombotic effect.

Neurofilaments bind tubulin and modulate its polymerization.

Neurofilaments assemble from three intermediate-filament proteins, contribute to the radial growth of axons, and are exceptionally stable. Microtubules are dynamic structures that assemble from tubulin dimers to support intracellular transport of molecules and organelles. We show here that neurofilaments, and other intermediate-filament proteins, contain motifs in their N-terminal domains that bind unassembled tubulin. Peptides containing such motifs inhibit the in vitro polymerization of microtubules and can be taken up by cultured cells in which they disrupt microtubules leading to altered cell shapes and an arrest of division. In transgenic mice in which neurofilaments are withheld from the axonal compartment, axonal tubulin accumulation is normal but microtubules assemble in excessive numbers. These observations suggest a model in which axonal neurofilaments modulate local microtubule assembly. This capacity also suggests novel mechanisms through which inherited or acquired disruptions in intermediate filaments might contribute to pathogenesis in multiple conditions.

Cutaneous neurofibromas: patients' medical burden, current management and therapeutic expectations: results from an online European patient community survey.

BACKGROUND: Neurofibromatosis type 1 is an inherited condition with variable phenotypic expression and a high medical and social burden. The objectives of this patient survey were to better understand the real-world experiences of patients living with cutaneous neurofibromas (cNF), to perceive their satisfaction and feelings about cNF current management (only laser and surgery are currently available), and to highlight their expectations of new therapeutic modalities. RESULTS: One hundred seventy patients from 4 European countries took part in the study, 65% (n = 110) were women and mean age was 39 years old. 96% (n = 164) of respondents have cNF on visible parts of the body and the survey confirmed that total number of cNF and visibility increase with age. Patients reported that cNF mainly impacts everyday mood, general daily life and social life. The visibility of cNF had a higher impact than their number. 92% (n = 156) of patients have a regular and multidisciplinary medical follow-up. The dermatologist is one of the most consulted healthcare professionals. 76% (n = 130) of respondents have treated their cNF: 65% (n = 111) had surgery and 38% (n = 64) had multiple laser sessions. Frequency of operations and regrowth of cNF were the two most unsatisfactory aspects with both treatments for patients. Indeed, after removal, new cNF appear in more than 75% (n = 128) of cases. As a future treatment, patients expected a topical (30%, n = 51) or oral medication (29%, n = 50). Around 2 out of 3 patients would agree to take it at least once a day or more for life but they would like a well-tolerated treatment. According to patients, the most important effectiveness criteria of a new treatment are to block cNF growth and reduce their number. 70% (n = 119) of patients would consider a future treatment moderately effective to very effective if it could clear 30% of cNF. CONCLUSIONS: This first cNF European patient community survey confirmed that the visible stigma and unaesthetic aspect of cNF have an important impact on patients' quality of life. The survey highlighted that patients were not entirely satisfied with the actual surgery and laser treatments and revealed their clear and realistic expectations for future treatment of cNF.

Review of the multiple aspects of neurofilament functions, and their possible contribution to neurodegeneration.

Neurofilaments (NF) are the most abundant cytoskeletal component of large myelinated axons from adult central and peripheral nervous system. Here, we provide an overview of the complementary approaches, including biochemistry, cell biology and transgenic technology that were used to investigate the assembly, axonal transport and functions of NF in normal and pathological situations. Following their synthesis and assembly in the cell body, NFs are transported along the axon. This process is finely regulated via phosphorylation of the carboxy-terminal part of the two high-molecular-weight subunits of NF. The correct formation of an axonal network of NF is crucial for the establishment and maintenance of axonal calibre and consequently for the optimisation of conduction velocity. The frequent disorganisation of NF network observed in several neuropathologies support their contribution. However, despite the presence of NF mutations found in some patients, the exact relations between these mutations, the abnormal NF organisation and the pathological process remain a challenging field of investigation.

Effects of red wine polyphenols on postischemic neovascularization model in rats: low doses are proangiogenic, high doses anti-angiogenic.

Polyphenols, present in green tea, grapes, or red wine, have paradoxical properties: they protect against cardiac and cerebral ischemia but inhibit angiogenesis in vitro. So we investigated the effects of polyphenols in vivo on postischemic neovascularization. Rats treated with low (0.2 mg x kg(-1) x day(-1)) or high (20 mg x kg(-1) x day(-1)) doses of red wine polyphenolic compounds (RWPC) were submitted to femoral artery ligature on the left leg. Two wks after ligature, high doses of RWPC (i.e., 7 glasses of red wine) reduced arterial, arteriolar, and capillary densities and blood flow in association with an inhibition of a PI3 kinase-Akt-endothelial NO synthase (eNOS) pathway, decreased VEGF expression, and lower metalloproteinase (MMP) activation. Low doses of RWPC (i.e., 1/10th glass of red wine) increased the left/right (L/R) leg ratio to control level in association with an increased blood flow and microvascular density. This angiogenic effect was associated with an overexpression of PI3 kinase-Akt-eNOS pathway and an increased VEGF production without effect on MMP activation. Thus, low and high doses RWPC have respectively pro- and anti-angiogenic properties on postischemic neovascularization in vivo. This unique dual effect of RWPC offers important perspectives for the treatment and prevention of ischemic diseases (low dose) or cancer growth (high dose).

Protease-activated receptor 1 antagonists prevent platelet aggregation and adhesion without affecting thrombin time.

The aim of this study was to investigate the in vitro antithrombotic effects of two PAR1 antagonists, ER121958 and SCH203099 on both SFLLR-induced platelet adhesion and aggregation and on the thrombin time in human and guinea-pig platelets. ER121958 inhibited SFLLR-induced guinea-pig and human platelet adhesion with the IC(50) values of 1.73nM and 2.91nM, respectively and SFLLR-induced guinea-pig and human platelet aggregation with the IC(50) values of 2.74nM and 11.9nM, respectively. Similarly, SCH203099 exhibited a non competitive profile of inhibition on both SFLLR-induced guinea-pig and human platelet adhesion with the IC(50) values of 93nM and 127nM, respectively or SFLLR-induced guinea-pig and human platelet aggregation with the IC(50) values of 1.74microM and 2.36microM, respectively. These two antagonists failed to prolong the thrombin time. Altogether, these results highlighted the potent anti-platelets properties of both ER121958 and SCH203099 in an in vitro model of aggregation as well as in a static model of adhesion without any effect on the last step of coagulation cascade. Moreover, this work emphasized that guinea-pig is a suitable animal model to study the role of PAR1 antagonists since the magnitude of the effects of ER121958 and SCH203099 on both SFLLR-induced platelet adhesion and aggregation were similar in both species.

Effects of a new PAR1 antagonist, F 16618, on smooth muscle cell contraction.

This study evaluated the effects of two PAR1 antagonists on vessels contracted by SFLLR. ER 121958 antagonized the SFLLR-induced contraction on rat denuded superior mesenteric artery and pig coronary artery in a non-competitive manner (IC(50) values were 22 [7.5-43.6] nM and 2.9 [2.09-4.02] nM, respectively). F 16618 inhibited the SFLLR-induced superior mesenteric arteries and coronary arteries contraction in a competitive manner (pA(2) values of 7.3 and 6.2, respectively). PAR1 antagonists do not affect vessel resting tension or haemodynamic parameters in anaesthetized rats. Thus, PAR1 antagonists could have beneficial effects against vasospasm due to vessel injury.

Discovery of novel protease activated receptors 1 antagonists with potent antithrombotic activity in vivo.

Protease activated receptors (PARs) or thrombin receptors constitute a class of G-protein-coupled receptors (GPCRs) implicated in the activation of many physiological mechanisms. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1. This article describes the discovery of new antagonists of these receptors and more specifically two compounds: 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)penta-1,3-dienyl]benzonitrile 36 (F 16618) and 3-(2-chlorophenyl)-1-[4-(4-fluorobenzyl)piperazin-1-yl]propenone 39 (F 16357), obtained after optimization. Both compounds are able to inhibit SFLLR-induced human platelet aggregation and display antithrombotic activity in an arteriovenous shunt model in the rat after iv or oral administration. Furthermore, these compounds are devoid of bleeding side effects often observed with other types of antiplatelet drugs, which constitutes a promising advantage for this new class of antithrombotic agents.

Key role of alpha(1)beta(1)-integrin in the activation of PI3-kinase-Akt by flow (shear stress) in resistance arteries.

Resistance arteries are the site of the earliest manifestations of many cardiovascular and metabolic diseases. Flow (shear stress) is the main physiological stimulus for the endothelium through the activation of vasodilatory pathways generating flow-mediated dilation (FMD). The role of FMD in local blood flow control and angiogenesis is well established, and alterations in FMD are early markers of cardiovascular disorders. alpha(1)-Integrin, which has a role in angiogenesis, could be involved in FMD. FMD was studied in mesenteric resistance arteries (MRA) isolated in arteriographs. The role of alpha(1)-integrins in FMD was tested with selective antibodies and mice lacking the gene encoding for alpha(1)-integrins. Both anti-alpha(1) blocking antibodies and genetic deficiency in alpha(1)-integrin in mice (alpha(1)(-/-)) inhibited FMD without affecting receptor-mediated (acetylcholine) endothelium-dependent dilation or endothelium-independent dilation (sodium nitroprusside). Similarly, vasoconstrictor tone (myogenic tone and phenylephrine-induced contraction) was not affected. In MRA phosphorylated Akt and phosphatidylinositol 3-kinase (PI3-kinase) were significantly lower in alpha(1)(-/-) mice than in alpha(1)(+/+) mice, although total Akt and endothelial nitric oxide synthase (eNOS) were not affected. Pharmacological blockade of PI3-kinase-Akt pathway with LY-294002 inhibited FMD. This inhibitory effect of LY-294002 was significantly lower in alpha(1)(-/-) mice than in alpha(1)(+/+) mice. Thus alpha(1)-integrin has a key role in flow (shear stress)-dependent vasodilation in resistance arteries by transmitting the signal to eNOS through activation of PI3-kinase and Akt. Because of the central role of flow (shear stress) activation of the endothelium in vascular disorders, this finding opens new perspectives in the pathophysiology of the microcirculation and provides new therapeutic targets.

Paradoxical role of angiotensin II type 2 receptors in resistance arteries of old rats.

The role of angiotensin II type 2 receptors (AT2Rs) remains a matter of controversy. Its vasodilatory and antitrophic properties are well accepted. Nevertheless, in hypertensive rats, AT2R stimulation induces a vasoconstriction counteracting flow-mediated dilation (FMD). This contraction is reversed by hydralazine. Because FMD is also decreased in aging, another risk factor for cardiovascular diseases, we hypothesized that AT2R function might be altered in old-rat resistance arteries. Mesenteric resistance arteries (250 mum in diameter) were isolated from old (24 months) and control (4 months) rats receiving hydralazine (16 mg/kg per day; 2 weeks) or water. FMD, NO-mediated dilation, and endothelial NO synthase expression were lower in old versus control rats. AT2R blockade improved FMD in old rats, suggesting that AT2R stimulation produced vasoconstriction. AT2R expression was higher in old rats and mainly located in the smooth muscle layer. In old rats, AT2R stimulation induced endothelium-independent contraction, which was suppressed by the antioxidant Tempol. Reactive oxygen species level was higher in old-rat arteries than in controls. Hydralazine improved FMD and NO-dependent dilation in old rats without change in AT2R expression and location. In old rats treated with hydralazine, reactive oxygen species level was reduced in endothelial and smooth muscle cells, and AT2R-dependent contraction was abolished. Thus, AT2R stimulation induced vasoconstriction through activation of reactive oxygen species production, contributing to decrease FMD in old-rat resistance arteries. Hydralazine suppressed AT2R-dependent reactive oxygen species production and AT2R-dependent contraction, improving FMD. Importantly, endothelial alterations in aging were reversible. These findings are important to consider in the choice of vasoactive drugs in aging.

Flow-induced remodeling in resistance arteries from obese Zucker rats is associated with endothelial dysfunction.

Chronic increases in blood flow increase arterial diameter and NO-dependent dilation in resistance arteries. Because endothelial dysfunction accompanies metabolic syndrome, we hypothesized that flow-mediated remodeling might be impaired in obese rat resistance arteries. Obese and lean Zucker rat mesenteric resistance arteries were exposed to chronic flow increases through arterial ligation in vivo: arteries exposed to high flow were compared with normal flow arteries. Diameter was measured in vitro in cannulated arteries using pressure arteriography. After 7 days, outward remodeling (diameter increased from 346+/-9 to 412+/-11 mum at 100 mm Hg) occurred in lean high-flow arteries. Endothelium-dependent tone was reduced in high-flow arteries from obese rats by contrast with lean animals. On the other hand, diameter enlargement occurred similarly in the 2 strains. The involvement of NO in endothelium-dependent dilation (evidenced by NO blockade) and endothelial NO synthase phosphorylation was smaller in obese than in lean rats. Superoxide anion and reduced nicotinamide-adenine dinucleotide phosphate oxidase subunit expression (p67phox and gp91phox) increased in obese rats and were higher in high-flow than in control arteries. Acute Tempol (a catalase mimetic), catalase plus superoxide dismutase, and l-arginine plus tetrahydrobiopterin restored endothelium-dependent dilation in obese rat normal and high-flow arteries to the level found in lean control arteries. Thus, flow-induced remodeling in obese resistance arteries was associated with a reduced endothelium-mediated dilation because of a decreased NO bioavailability and an excessive superoxide production. This dysfunction might have negative consequences in ischemic diseases in patients with obesity or metabolic syndrome.