Cytoprotective pathways in the vascular endothelium. Do they represent a viable therapeutic target?

The vascular endothelium is a critical interface, which separates the organs from the blood and its contents. The endothelium has a wide variety of functions and maintenance of endothelial homeostasis is a multi-dimensional active process, disruption of which has potentially deleterious consequences if not reversed. Vascular injury predisposes to endothelial apoptosis, dysfunction and development of atherosclerosis. Endothelial dysfunction is an end-point, a central feature of which is increased ROS generation, a reduction in endothelial nitric oxide synthase and increased nitric oxide consumption. A dysfunctional endothelium is a common feature of diseases including rheumatoid arthritis, systemic lupus erythematosus, diabetes mellitus and chronic renal impairment. The endothelium is endowed with a variety of constitutive and inducible mechanisms that act to minimise injury and facilitate repair. Endothelial cytoprotection can be enhanced by exogenous factors such as vascular endothelial growth factor, prostacyclin and laminar shear stress. Target genes include endothelial nitric oxide synthase, heme oxygenase-1, A20 and anti-apoptotic members of the B cell lymphoma protein-2 family. In light of the importance of endothelial function, and the link between its disruption and the risk of atherothrombosis, interest has focused on therapeutic conditioning and reversal of endothelial dysfunction. A detailed understanding of cytoprotective signalling pathways, their regulation and target genes is now required to identify novel therapeutic targets. The ultimate aim is to add vasculoprotection to current therapeutic strategies for systemic inflammatory diseases, in an attempt to reduce vascular injury and prevent or retard atherogenesis

The efficacy of antihypertensiye drugs in chronic intermittent hypoxia conditions

The authors would like to thank the Portuguese Fundacao para a Ciencia e a Tecnologia (FCT) and CEDOC (Chronic Diseases Research Centre, Lisbon, Portugal). Lucilia N. Diogo is supported by an FCT fellowship (SFRH/BD/48335/2008; PTDC/SAU-TOX/112264/2009).Sleep apnea/hypopnea disorders include centrally originated diseases and obstructive sleep apnea (OSA). This last condition is renowned as a frequent secondary cause of hypertension (HT). The mechanisms involved in the pathogenesis of HT can be summarized in relation to two main pathways: sympathetic nervous system stimulation mediated mainly by activation of carotid body (CB) chemoreflexes and/or asphyxia, and, by no means the least important, the systemic effects of chronic intermittent hypoxia (CIH). The use of animal models has revealed that CIH is the critical stimulus underlying sympathetic activity and hypertension, and that this effect requires the presence of functional arterial chemoreceptors, which are hyperactive in CIH. These models of CIH mimic the HT observed in humans and allow the study of CIH independently without the mechanical obstruction component. The effect of continuous positive airway pressure (CRAP), the gold standard treatment for OSA patients, to reduce blood pressure seems to be modest and concomitant antihypertensive therapy is still required. We focus this review on the efficacy of pharmacological interventions to revert HT associated with CIH conditions in both animal models and humans. First, we explore the experimental animal models, developed to mimic HT related to CIH, which have been used to investigate the effect of antihypertensive drugs (AHDs). Second, we review what is known about drug efficacy to reverse HT induced by CIH in animals. Moreover, findings in humans with OSA are cited to demonstrate the lack of strong evidence for the establishment of a first-line antihypertensive regimen for these patients. Indeed, specific therapeutic guidelines for the pharmacological treatment of HT in these patients are still lacking. Finally, we discuss the future perspectives concerning the non-pharmacological and pharmacological management of this particular type of HT.publishersversionpublishe

Dysfonction endothéliale et polyarthrite rhumatoïde : cinétique, mécanismes et traitements. Etude chez le rat

Rheumatoid arthritis (RA) is the most common systemic autoimmune disease which is associated with excessive cardiovascular (CV) mortality and morbidity. Endothelial dysfunction (ED) has been identified as a key element in the development of atherosclerosis and CV complications in RA. However, both pathophysiology and therapeutic options of ED are still ill-defined. In this work we aimed to determine the time-course of ED in RA, the differences of ED between macro- and microvasculature, the link between ED and circulating markers of inflammation or endothelial activation, and the effect of an anti-TNFα agent, Etanercept, for reversing ED. Experiments have been conducted on the model of adjuvant-induced arthritis (AIA) in Lewis rats. Endothelial function was assessed in isolated aortic rings (macrovasculature) and in isolated mesenteric arteries (microvasculature). In a first study, we showed that ED occurred earlier in microvascular bed (first symptoms of arthritis) than in macrovascular bed (at maximal inflammation), and is more sustainable. Circulating levels of CRP, ICAM-1 and VCAM-1 cannot be used as markers of ED in arthritis.In a second study, we characterized the mechanisms involved in ED in AIA rats. Our results showed that despite the absence of aortic ED in the early stage of arthritis (first symptoms of arthritis), endothelial abnormalities are already present but initially compensated by an increase in NOS activity. We identified plasma levels of IL-1β, TNF-α and MIP-1α as potential circulating markers of macrovascular ED in RA.Our third study demonstrated the ability of a curative treatment with Etanercept, an anti-TNFα, to improve endothelial function in the AIA model, regardless its impact on traditional CV risk factors and on the severity of the diseaseIn conclusion, our results led to improve the understanding of ED in case of arthritis. They provide diagnostic and therapeutic perspectives to enhance the management of CV risk in RA patientsLa polyarthrite rhumatoïde (PR) représente le plus fréquent des rhumatismes inflammatoires chroniques. En plus d’une atteinte ostéo-articulaire responsable de l’invalidité fonctionnelle, la PR est associée à une surmortalité d’origine cardiovasculaire (CV). Les données récentes de la littérature identifient la dysfonction endothéliale (DE) comme la pierre angulaire du processus athéromateux et des complications CV au cours de la PR. Cependant, la physiopathologie et les possibilités thérapeutiques de cette DE sont mal connues. L’objectif de mon travail a été d’étudier la cinétique de la DE au cours de la PR, la différence de sa survenue entre les lits macrovasculaire et microvasculaire, le lien entre la DE et des marqueurs circulants d’inflammation ou d’activation endothéliale, et l’impact de l’Etanercept, un anti-TNFα utilisé comme traitement de fond de la PR, sur la DE. Les expériences ont été réalisées sur le modèle d’Arthrite Induite à l’Adjuvant (AIA) chez le rat Lewis, la fonction endothéliale étant étudiée sur des anneaux aortiques isolés (macrocirculation) ou des artères mésentériques isolées (microcirculation).Dans la première étude, nous avons montré que la DE microvasculaire est d’apparition plus précoce que la DE macrovasculaire (premiers symptômes d’arthrite versus inflammation maximale), et plus durable. Les taux circulants de CRP, ICAM-1 et VCAM-1 ne peuvent pas être utilisés comme marqueurs de DE dans l’arthrite.Dans la deuxième étude, nos résultats ont montré que, malgré l’absence de DE aortique au stade précoce de l’arthrite (premiers symptômes d’arthrite), les anomalies endothéliales sont déjà présentes mais initialement compensées par une augmentation de l’activité de la NOS. Nous avons identifié l’IL-1β, le TNF-α et le MIP-1α plasmatiques comme des marqueurs circulants potentiels de la DE macrovasculaire dans la PR.Notre troisième étude a démontré la capacité d’un traitement curatif par Etanercept : un anti TNF-α, à améliorer la fonction endothéliale dans le modèle AIA, indépendamment de son impact sur les facteurs traditionnels de risque CV et sur la sévérité de la maladie.En conclusion, nos travaux ont permis de mieux comprendre la DE en cas d’arthrite, et ont apporté des éléments qui ouvrent des perspectives diagnostiques et thérapeutiques pour une meilleure prise en charge du risque CV du patient P

Endothelial dysfunction and rheumatoïd arthritis : time-course, mechanisms and treatment. Study in adjuvant-induced arthritis rat model

La polyarthrite rhumatoïde (PR) représente le plus fréquent des rhumatismes inflammatoires chroniques. En plus d’une atteinte ostéo-articulaire responsable de l’invalidité fonctionnelle, la PR est associée à une surmortalité d’origine cardiovasculaire (CV). Les données récentes de la littérature identifient la dysfonction endothéliale (DE) comme la pierre angulaire du processus athéromateux et des complications CV au cours de la PR. Cependant, la physiopathologie et les possibilités thérapeutiques de cette DE sont mal connues. L’objectif de mon travail a été d’étudier la cinétique de la DE au cours de la PR, la différence de sa survenue entre les lits macrovasculaire et microvasculaire, le lien entre la DE et des marqueurs circulants d’inflammation ou d’activation endothéliale, et l’impact de l’Etanercept, un anti-TNFα utilisé comme traitement de fond de la PR, sur la DE. Les expériences ont été réalisées sur le modèle d’Arthrite Induite à l’Adjuvant (AIA) chez le rat Lewis, la fonction endothéliale étant étudiée sur des anneaux aortiques isolés (macrocirculation) ou des artères mésentériques isolées (microcirculation).Dans la première étude, nous avons montré que la DE microvasculaire est d’apparition plus précoce que la DE macrovasculaire (premiers symptômes d’arthrite versus inflammation maximale), et plus durable. Les taux circulants de CRP, ICAM-1 et VCAM-1 ne peuvent pas être utilisés comme marqueurs de DE dans l’arthrite.Dans la deuxième étude, nos résultats ont montré que, malgré l’absence de DE aortique au stade précoce de l’arthrite (premiers symptômes d’arthrite), les anomalies endothéliales sont déjà présentes mais initialement compensées par une augmentation de l’activité de la NOS. Nous avons identifié l’IL-1β, le TNF-α et le MIP-1α plasmatiques comme des marqueurs circulants potentiels de la DE macrovasculaire dans la PR.Notre troisième étude a démontré la capacité d’un traitement curatif par Etanercept : un anti TNF-α, à améliorer la fonction endothéliale dans le modèle AIA, indépendamment de son impact sur les facteurs traditionnels de risque CV et sur la sévérité de la maladie.En conclusion, nos travaux ont permis de mieux comprendre la DE en cas d’arthrite, et ont apporté des éléments qui ouvrent des perspectives diagnostiques et thérapeutiques pour une meilleure prise en charge du risque CV du patient PRRheumatoid arthritis (RA) is the most common systemic autoimmune disease which is associated with excessive cardiovascular (CV) mortality and morbidity. Endothelial dysfunction (ED) has been identified as a key element in the development of atherosclerosis and CV complications in RA. However, both pathophysiology and therapeutic options of ED are still ill-defined. In this work we aimed to determine the time-course of ED in RA, the differences of ED between macro- and microvasculature, the link between ED and circulating markers of inflammation or endothelial activation, and the effect of an anti-TNFα agent, Etanercept, for reversing ED. Experiments have been conducted on the model of adjuvant-induced arthritis (AIA) in Lewis rats. Endothelial function was assessed in isolated aortic rings (macrovasculature) and in isolated mesenteric arteries (microvasculature). In a first study, we showed that ED occurred earlier in microvascular bed (first symptoms of arthritis) than in macrovascular bed (at maximal inflammation), and is more sustainable. Circulating levels of CRP, ICAM-1 and VCAM-1 cannot be used as markers of ED in arthritis.In a second study, we characterized the mechanisms involved in ED in AIA rats. Our results showed that despite the absence of aortic ED in the early stage of arthritis (first symptoms of arthritis), endothelial abnormalities are already present but initially compensated by an increase in NOS activity. We identified plasma levels of IL-1β, TNF-α and MIP-1α as potential circulating markers of macrovascular ED in RA.Our third study demonstrated the ability of a curative treatment with Etanercept, an anti-TNFα, to improve endothelial function in the AIA model, regardless its impact on traditional CV risk factors and on the severity of the diseaseIn conclusion, our results led to improve the understanding of ED in case of arthritis. They provide diagnostic and therapeutic perspectives to enhance the management of CV risk in RA patient

Vasorelaxing effect of a TrkB receptor agonist on mesenteric arteries

International audienceIntroduction: Brain-derived neurotrophic factor (BDNF) is a neurotrophin unanimously recognized for its promoting effect on neuroplasticity and cognition, through activation of tropomyosin receptor kinase B (TrkB). In opposition with the traditional thinking that neurons are the main source of BDNF, endothelial cells were found to express large amounts of BDNF. Exogenous BDNF was reported to exert vasodilating properties on isolated pulmonary artery and aorta. However, whether peripheral vascular resistances are controlled by endothelial BDNF is not known. To address this question, we investigated the vasorelaxant properties and the underlying signaling pathways of a TrkB agonist (LM22A4) on mesenteric arteries in rat.Material and methods: Experiments were conducted on third-order mesenteric arteries harvested from 24 male Wistar rats (6–8 week-old) and mounted in isometric conditions. Intact or endothelium-denuded arteries were pre-constricted with phenylephrine (3 × 10−5 m) and relaxed with cumulative concentrations LM22A4 (10−11–10−4 m). Cyclotraxin B (10−6 m) was used as a TrkB antagonist. Vessels were also incubated with various specific inhibitors to assess the signaling pathways activated by LM22A4 including nitric oxide- (L-NAME, 10−4 m), endothelium-derived hyperpolarizing factor- (EDHF, apamin 10−7 m and charybdotoxin 10−7 m), PGI2- (U51605, 10−6 m), PI3K/Akt- (wortmannin 3 × 10−8 m), CaM/CaMKII (Calmidazolium 10−5 m, KN-62 10−5 m) and PLCγ- (U73122 10−5 m) dependent pathways.Results: Our results showed that LM22A4 induced vasorelaxation in mesenteric arteries, with maximal effect Emax 51 ± 7% and concentration for 50% of maximal effect (EC50) of approximately 0.025 μm. Endothelium removal as well as cyclotraxin B significantly blunted the effect of LM22A4. In addition, endothelium-dependent relaxant effect of LM22A4 was reduced by inhibitors of NO, EDHF, PGI2 production and PI3K/Akt signaling pathways. By contrast, vasodilating effect of LM22A4 was not modified by inhibition of CaM/CaMKII and PLCγ pathways.Discussion/Conclusion: In conclusion, our data demonstrated for the first time the capacity of a TrkB agonist to vasodilate peripheral resistance arteries. This effect involved activation of endothelial TrkB receptors and relied on production of NO, EDHF, PGI2 and activation of PI3K/Akt pathway. These data, combined with evidence that endothelial BDNF expression is decreased by hypertension and increased by physical training, suggest a possible role of BDNF in endothelial dysfunction

Contextualized phosphorus recycling: potential diminution of phosphorus criticality at territory scale - Application to agricultural LCA

International audiencePhosphate rock is classified as critical raw material for the European Union's economy. It provides phosphorus (P), which is an essential element for food production and is used as a mineral fertilizer. Due to a lack of a phosphorus substitute in fertilization, recycling is presently the only solution to reduce criticality, especially for countries such as France, that has no phosphate rock reserve and thus, must depend on foreign countries for its P needs for agricultural purposes. MAFOR or fertilizer mineral/organic matter from waste can contain available phosphorus. However, the recycling of P from these deposits for agriculture involves many actors (farmers, regulators, etc.) and depends on the studied spatial scale and its context (economic, regulatory, social, etc.) which can be either constraints or drivers for P recycling. Nevertheless, these issues are not taken into account in the recycling rate used in the raw material criticality assessment nor in the LCA methods. Therefore, it is necessary to contextualize P recycling for a better understanding of phosphorus recycling, and to allow a relevant phosphorus criticality assessment and an environmental impact assessment of phosphorus recycling at a local scale. In order to achieve this, a contextualized model is developed. The goal is to be able to quantify phosphorus which would potentially be used by farmers, originated from the total available quantities of deposits, by respecting the context of the studied territory. The originality of the model lies in the integration of context-factors that can affect the use of P contained in MAFOR by farmers. As output of the model, four indicators are expected: the effectiveness and efficiency of phosphorus recycling, the dependence on phosphate mineral fertilizers imported from outside France and the contextualized balance between supply and demand in P recycling-derived fertilizers. The model gives a methodology advancement, which would improve or be a complement of the LCA tool to assess territorialized recycling scenarii. The output indicators would improve the understanding of P circularity and, help determine a suitable P recycling pathway to reduce P criticality at a territorial scale and relevant from an environmental point of view

Vasorelaxing effect of a TrkB receptor agonist on mesenteric arteries

International audienceIntroduction: Brain-derived neurotrophic factor (BDNF) is a neurotrophin unanimously recognized for its promoting effect on neuroplasticity and cognition, through activation of tropomyosin receptor kinase B (TrkB). In opposition with the traditional thinking that neurons are the main source of BDNF, endothelial cells were found to express large amounts of BDNF. Exogenous BDNF was reported to exert vasodilating properties on isolated pulmonary artery and aorta. However, whether peripheral vascular resistances are controlled by endothelial BDNF is not known. To address this question, we investigated the vasorelaxant properties and the underlying signaling pathways of a TrkB agonist (LM22A4) on mesenteric arteries in rat.Material and methods: Experiments were conducted on third-order mesenteric arteries harvested from 24 male Wistar rats (6–8 week-old) and mounted in isometric conditions. Intact or endothelium-denuded arteries were pre-constricted with phenylephrine (3 × 10−5 m) and relaxed with cumulative concentrations LM22A4 (10−11–10−4 m). Cyclotraxin B (10−6 m) was used as a TrkB antagonist. Vessels were also incubated with various specific inhibitors to assess the signaling pathways activated by LM22A4 including nitric oxide- (L-NAME, 10−4 m), endothelium-derived hyperpolarizing factor- (EDHF, apamin 10−7 m and charybdotoxin 10−7 m), PGI2- (U51605, 10−6 m), PI3K/Akt- (wortmannin 3 × 10−8 m), CaM/CaMKII (Calmidazolium 10−5 m, KN-62 10−5 m) and PLCγ- (U73122 10−5 m) dependent pathways.Results: Our results showed that LM22A4 induced vasorelaxation in mesenteric arteries, with maximal effect Emax 51 ± 7% and concentration for 50% of maximal effect (EC50) of approximately 0.025 μm. Endothelium removal as well as cyclotraxin B significantly blunted the effect of LM22A4. In addition, endothelium-dependent relaxant effect of LM22A4 was reduced by inhibitors of NO, EDHF, PGI2 production and PI3K/Akt signaling pathways. By contrast, vasodilating effect of LM22A4 was not modified by inhibition of CaM/CaMKII and PLCγ pathways.Discussion/Conclusion: In conclusion, our data demonstrated for the first time the capacity of a TrkB agonist to vasodilate peripheral resistance arteries. This effect involved activation of endothelial TrkB receptors and relied on production of NO, EDHF, PGI2 and activation of PI3K/Akt pathway. These data, combined with evidence that endothelial BDNF expression is decreased by hypertension and increased by physical training, suggest a possible role of BDNF in endothelial dysfunction

Association between endothelial dysfunction and brain BDNF levels in a rat model of arthritis

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Activation of endothelial TrkB receptors induces relaxation of resistance arteries

International audienceWhile brain-derived neurotrophic factor (BDNF) was previously reported to induce relaxation of conduit artery, whether the BDNF/TrkB (tropomyosin-related kinase) pathway is involved in the tone control of resistance arteries is not known. This study investigated TrkB receptors levels/localization and the vasomotor effect of the TrkB receptor agonist LM22A-4 in isolated third-order mesenteric arteries from rats.Immunostaining revealed the presence of both full-length and truncated TrkB receptors, especially at the endothelial level. By using wire myography, LM22A-4 induced vascular relaxation that was significantly decreased by cyclotraxin B as a non-competitive TrkB antagonist and fully prevented by endothelium removal. Inhibitors of NO, EDHF, PGI2 production and the PI3K/Akt pathways separately reduced LM22A-4 inducedrelaxation. By contrast, inhibition of Raf/MEK, PLC gamma and CaM/CaMKII pathways did not change the relaxant effect of LM22A-4. Interestingly, BDNF also induced an endothelium and TrkB-dependent relaxation.These results indicate that endothelial TrkB activation results in the relaxation of resistance vessels via PI3K/ Akt-induced eNOS phosphorylation and production of EDHF and PGI(2). These data are consistent with the contribution of the endothelial BDNF/TrkB pathway to the regulation of peripheral vascular tone. They also validate the use of LM22A-4 as a reliable pharmacological agent for studying the vascular effect of BDNF