Int J Mol Sci

The role of Hedgehog (Hh) signaling in vascular biology has first been highlighted in embryos by Pepicelli et al. in 1998 and Rowitch et al. in 1999. Since then, the proangiogenic role of the Hh ligands has been confirmed in adults, especially under pathologic conditions. More recently, the Hh signaling has been proposed to improve vascular integrity especially at the blood-brain barrier (BBB). However, molecular and cellular mechanisms underlying the role of the Hh signaling in vascular biology remain poorly understood and conflicting results have been reported. As a matter of fact, in several settings, it is currently not clear whether Hh ligands promote vessel integrity and quiescence or destabilize vessels to promote angiogenesis. The present review relates the current knowledge regarding the role of the Hh signaling in vasculature development, maturation and maintenance, discusses the underlying proposed mechanisms and highlights controversial data which may serve as a guideline for future research. Most importantly, fully understanding such mechanisms is critical for the development of safe and efficient therapies to target the Hh signaling in both cancer and cardiovascular/cerebrovascular diseases

Arterioscler Thromb Vasc Biol

Evidences accumulated within the past decades identified hedgehog signaling as a new regulator of endothelium integrity. More specifically, we recently identified Dhh (desert hedgehog) as a downstream effector of Klf2 (Kruppel-like factor 2) in endothelial cells (ECs). The purpose of this study is to investigate whether hedgehog coreceptors Gas1 (growth arrest-specific 1) and Cdon (cell adhesion molecule-related/downregulated by oncogenes) may be used as therapeutic targets to modulate Dhh signaling in ECs. Approach and Results: We demonstrated that both Gas1 and Cdon are expressed in adult ECs and relied on either siRNAs- or EC-specific conditional knockout mice to investigate their role. We found that Gas1 deficiency mainly phenocopies Dhh deficiency especially by inducing VCAM-1 (vascular cell adhesion molecule 1) and ICAM-1 (intercellular adhesion molecule 1) overexpression while Cdon deficiency has opposite effects by promoting endothelial junction integrity. At a molecular level, Cdon prevents Dhh binding to Ptch1 (patched-1) and thus acts as a decoy receptor for Dhh, while Gas1 promotes Dhh binding to Smo (smoothened) and as a result potentiates Dhh effects. Since Cdon is upregulated in ECs treated by inflammatory cytokines, including TNF (tumor necrosis factor)-α and Il (interleukin)-1β, we then tested whether Cdon inhibition would promote endothelium integrity in acute inflammatory conditions and found that both fibrinogen and IgG extravasation were decreased in association with an increased Cdh5 (cadherin-5) expression in the brain cortex of EC-specific Cdon knockout mice administered locally with Il-1β. Altogether, these results demonstrate that Gas1 is a positive regulator of Dhh in ECs while Cdon is a negative regulator. Interestingly, Cdon blocking molecules may then be used to promote endothelium integrity, at least in inflammatory conditions

PLoS Biol

Inflammation of the central nervous system (CNS) induces endothelial blood-brain barrier (BBB) opening as well as the formation of a tight junction barrier between reactive astrocytes at the Glia Limitans. We hypothesized that the CNS parenchyma may acquire protection from the reactive astrocytic Glia Limitans not only during neuroinflammation but also when BBB integrity is compromised in the resting state. Previous studies found that astrocyte-derived Sonic hedgehog (SHH) stabilizes the BBB during CNS inflammatory disease, while endothelial-derived desert hedgehog (DHH) is expressed at the BBB under resting conditions. Here, we investigated the effects of endothelial Dhh on the integrity of the BBB and Glia Limitans. We first characterized DHH expression within endothelial cells at the BBB, then demonstrated that DHH is down-regulated during experimental autoimmune encephalomyelitis (EAE). Using a mouse model in which endothelial Dhh is inducibly deleted, we found that endothelial Dhh both opens the BBB via the modulation of forkhead box O1 (FoxO1) transcriptional activity and induces a tight junctional barrier at the Glia Limitans. We confirmed the relevance of this glial barrier system in human multiple sclerosis active lesions. These results provide evidence for the novel concept of "chronic neuroinflammatory tolerance" in which BBB opening in the resting state is sufficient to stimulate a protective barrier at the Glia Limitans that limits the severity of subsequent neuroinflammatory disease. In summary, genetic disruption of the BBB generates endothelial signals that drive the formation under resting conditions of a secondary barrier at the Glia Limitans with protective effects against subsequent CNS inflammation. The concept of a reciprocally regulated CNS double barrier system has implications for treatment strategies in both the acute and chronic phases of multiple sclerosis pathophysiology

Role of endothelial cell dysfunction in the pathophysiology of heart failure

L’insuffisance cardiaque engendre un décès toutes les 7 minutes en France. Cependant, il n’existe aucun traitement pour l’insuffisance cardiaque à fraction d’éjection préservée (ICFEp) qui représente aujourd’hui 50% des cas d’insuffisance cardiaque et dont la prévalence augmente constamment avec le vieillissement de la population. Mieux comprendre l’étiologie et la physiopathologie de cette maladie est primordial pour découvrir des thérapies efficaces pour la prise en charge de cette maladie. L’objectif de cette thèse est d’explorer le rôle de la maladie des petits vaisseaux dans la physiopathologie de l’ICFEp. Plus précisément, nous nous sommes attachés (1) à mieux caractériser le phénotype des capillaires cardiaques chez des souris présentant une dysfonction diastolique, (2) à caractériser les conséquences d’une dysfonction endothéliale sur la structure et la fonction cardiaque et (3) à mieux appréhender les mécanismes moléculaires impliqués dans la régulation de l’intégrité endothéliale par la voie de signalisation Hedgehog (Hh).Nous avons démontré pour la première fois dans un modèle physiopathologique d’ICFEp que les mastocytes sont des acteurs cruciaux du développement de la maladie des microvaisseaux et de la dysfonction diastolique. Nous avons également établi qu’une dysfonction endothéliale caractérisée principalement par une augmentation de la perméabilité vasculaire peut induire une dysfonction diastolique en absence de tout autre facteur de risque cardiovasculaire. En outre, nous avons démontré que le ligand Desert Hedgehog maintient l’intégrité vasculaire en régulant la dégradation de la métalloprotéinase Adam17 dans les cellules endothéliales.L’ensemble de ces résultats démontrent le rôle crucial de la dysfonction endothéliale dans la physiopathologie de l’ICFEp, ainsi que le rôle majeur de Dhh et de la voie de signalisation Hh dans l’intégrité vasculaire notamment dans le cœur.Heart failure causes one death every 7 minutes in France. Yet, there is no treatment for heart failure with preserved ejection fraction (HFpEF) which represents 50% of heart failure cases and of which prevalence increases constantly with the aging of the population. A better understanding of the etiology and pathophysiology of this disease is primordial to discover efficient therapeutics for its treatment. The objective of this thesis is to explore the role of microvessels disease in the pathophysiology of HFpEF. More precisely, we strive (1) to better characterize the cardiac capillaries phenotype in mice presenting a diastolic dysfunction, (2) to characterize the consequences of an endothelial dysfunction on the cardiac structure and function and (3) to better understand the molecular mechanisms implicated in the regulation of endothelial integrity by the Hedgehog (Hh) signaling pathway.We demonstrated for the first time in pathophysiological model of HFpEF that mast cells are crucial players in the development of the microvessels disease and diastolic dysfunction. We also established that an endothelial dysfunction mainly characterized by an increased in vascular permeability can induce a diastolic dysfunction, without any cardiovascular risk factor. Furthermore, we showed that Desert Hedgehog ligand maintains vascular integrity by regulating the degradation of the metalloprotease Adam17 in endothelial cells.Overall, there results show the crucial role of endothelial dysfunction in the pathophysiology of HFpEF, as well as the major role of Dhh and the Hh signaling pathway in the vascular integrity, notably in the heart

Rôle de la dysfonction endothéliale dans la physiopathologie de l'insuffisance cardiaque

Heart failure causes one death every 7 minutes in France. Yet, there is no treatment for heart failure with preserved ejection fraction (HFpEF) which represents 50% of heart failure cases and of which prevalence increases constantly with the aging of the population. A better understanding of the etiology and pathophysiology of this disease is primordial to discover efficient therapeutics for its treatment. The objective of this thesis is to explore the role of microvessels disease in the pathophysiology of HFpEF. More precisely, we strive (1) to better characterize the cardiac capillaries phenotype in mice presenting a diastolic dysfunction, (2) to characterize the consequences of an endothelial dysfunction on the cardiac structure and function and (3) to better understand the molecular mechanisms implicated in the regulation of endothelial integrity by the Hedgehog (Hh) signaling pathway.We demonstrated for the first time in pathophysiological model of HFpEF that mast cells are crucial players in the development of the microvessels disease and diastolic dysfunction. We also established that an endothelial dysfunction mainly characterized by an increased in vascular permeability can induce a diastolic dysfunction, without any cardiovascular risk factor. Furthermore, we showed that Desert Hedgehog ligand maintains vascular integrity by regulating the degradation of the metalloprotease Adam17 in endothelial cells.Overall, there results show the crucial role of endothelial dysfunction in the pathophysiology of HFpEF, as well as the major role of Dhh and the Hh signaling pathway in the vascular integrity, notably in the heart.L’insuffisance cardiaque engendre un décès toutes les 7 minutes en France. Cependant, il n’existe aucun traitement pour l’insuffisance cardiaque à fraction d’éjection préservée (ICFEp) qui représente aujourd’hui 50% des cas d’insuffisance cardiaque et dont la prévalence augmente constamment avec le vieillissement de la population. Mieux comprendre l’étiologie et la physiopathologie de cette maladie est primordial pour découvrir des thérapies efficaces pour la prise en charge de cette maladie. L’objectif de cette thèse est d’explorer le rôle de la maladie des petits vaisseaux dans la physiopathologie de l’ICFEp. Plus précisément, nous nous sommes attachés (1) à mieux caractériser le phénotype des capillaires cardiaques chez des souris présentant une dysfonction diastolique, (2) à caractériser les conséquences d’une dysfonction endothéliale sur la structure et la fonction cardiaque et (3) à mieux appréhender les mécanismes moléculaires impliqués dans la régulation de l’intégrité endothéliale par la voie de signalisation Hedgehog (Hh).Nous avons démontré pour la première fois dans un modèle physiopathologique d’ICFEp que les mastocytes sont des acteurs cruciaux du développement de la maladie des microvaisseaux et de la dysfonction diastolique. Nous avons également établi qu’une dysfonction endothéliale caractérisée principalement par une augmentation de la perméabilité vasculaire peut induire une dysfonction diastolique en absence de tout autre facteur de risque cardiovasculaire. En outre, nous avons démontré que le ligand Desert Hedgehog maintient l’intégrité vasculaire en régulant la dégradation de la métalloprotéinase Adam17 dans les cellules endothéliales.L’ensemble de ces résultats démontrent le rôle crucial de la dysfonction endothéliale dans la physiopathologie de l’ICFEp, ainsi que le rôle majeur de Dhh et de la voie de signalisation Hh dans l’intégrité vasculaire notamment dans le cœur

Role of Hedgehog Signaling in Vasculature Development, Differentiation, and Maintenance

International audienceThe role of Hedgehog (Hh) signaling in vascular biology has first been highlighted in embryos by Pepicelli et al. in 1998 and Rowitch et al. in 1999. Since then, the proangiogenic role of the Hh ligands has been confirmed in adults, especially under pathologic conditions. More recently, the Hh signaling has been proposed to improve vascular integrity especially at the blood-brain barrier (BBB). However, molecular and cellular mechanisms underlying the role of the Hh signaling in vascular biology remain poorly understood and conflicting results have been reported. As a matter of fact, in several settings, it is currently not clear whether Hh ligands promote vessel integrity and quiescence or destabilize vessels to promote angiogenesis. The present review relates the current knowledge regarding the role of the Hh signaling in vasculature development, maturation and maintenance, discusses the underlying proposed mechanisms and highlights controversial data which may serve as a guideline for future research. Most importantly, fully understanding such mechanisms is critical for the development of safe and efficient therapies to target the Hh signaling in both cancer and cardiovascular/cerebrovascular diseases

Cardiovasc Res

The therapeutic potential of Hedgehog (Hh) signalling agonists for vascular diseases is of growing interest. However, molecular and cellular mechanisms underlying the role of the Hh signalling in vascular biology remain poorly understood. The purpose of the present paper is to clarify some conflicting literature data. : With this goal we have demonstrated that, unexpectedly, ectopically administered N-terminal Sonic Hedgehog (N-Shh) and endogenous endothelial-derived Desert Hedgehog (Dhh) induce opposite effects in endothelial cells (ECs). Notably, endothelial Dhh acts under its full-length soluble form (FL-Dhh) and activates Smoothened in ECs, while N-Shh inhibits it. At molecular level, N-Shh prevents FL-Dhh binding to Patched-1 demonstrating that N-Shh acts as competitive antagonist to FL-Dhh. Besides, we found that even though FL-Hh ligands and N-Hh ligands all bind Patched-1, they induce distinct Patched-1 localization. Finally, we confirmed that in a pathophysiological setting i.e. brain inflammation, astrocyte-derived N-Shh act as a FL-Dhh antagonist. The present study highlights for the first time that FL-Dhh and N-Hh ligands have antagonistic properties especially in ECs. As a consequence, Hh ligands or forms of Hh ligands cannot be used instead of another for therapeutic purposes

Arterioscler Thromb Vasc Biol

[Figure: see text]

Restoring Endothelial Function by Targeting Desert Hedgehog Downstream of Klf2 Improves Critical Limb Ischemia in Adults

RATIONALE: Klf (kruppel-like factor) 2 is critical to establish and maintain endothelial integrity. OBJECTIVE: Therefore, determining upstream and downstream mediators of Klf2 would lead to alternative therapeutic targets in cardiovascular disease management. METHODS AND RESULTS: Here we identify Dhh (desert hedgehog) as a downstream effector of Klf2, whose expression in endothelial cells (ECs) is upregulated by shear stress and decreased by inflammatory cytokines. Consequently, we show that Dhh knockdown in ECs promotes endothelial permeability and EC activation and that Dhh agonist prevents TNF-α (tumor necrosis factor alpha) or glucose-induced EC dysfunction. Moreover, we demonstrate that human critical limb ischemia, a pathological condition linked to diabetes mellitus and inflammation, is associated to major EC dysfunction. By recreating a complex model of critical limb ischemia in diabetic mice, we found that Dhh-signaling agonist significantly improved EC function without promoting angiogenesis, which subsequently improved muscle perfusion. CONCLUSION: Restoring EC function leads to significant critical limb ischemia recovery. Dhh appears to be a promising target, downstream of Klf2, to prevent the endothelial dysfunction involved in ischemic vascular diseases