Reduced expression of microRNA-130a promotes endothelial cell senescence and age-dependent impairment of neovascularization.

Aging is associated with impaired neovascularization in response to ischemia. MicroRNAs are small noncoding RNAs emerging as key regulators of physiological and pathological processes. Here we investigated the potential role of microRNAs in endothelial cell senescence and age-dependent impairment of neovascularization. Next generation sequencing and qRT-PCR analyses identified miR-130a as a pro-angiogenic microRNA which expression is significantly reduced in old mouse aortic endothelial cells (ECs). Transfection of young ECs with a miR-130a inhibitor leads to accelerated senescence and reduced angiogenic functions. Conversely, forced expression of miR-130a in old ECs reduces senescence and improves angiogenesis. In a mouse model of hindlimb ischemia, intramuscular injection of miR-130a mimic in older mice restores blood flow recovery and vascular densities in ischemic muscles, improves mobility and reduces tissue damage. miR-130a directly targets antiangiogenic homeobox genes MEOX2 and HOXA5. MEOX2 and HOXA5 are significantly increased in the ischemic muscles of aging mice, but forced expression of miR-130a reduces the expression of these factors. miR-130a treatment after ischemia is also associated with increased number and improved functional activities of pro-angiogenic cells (PACs). Forced expression of miR-130a could constitute a novel strategy to improve blood flow recovery and reduce ischemia in older patients with ischemic vascular diseases.

Neonatal exposure to high oxygen levels leads to impaired ischemia-induced neovascularization in adulthood.

Adverse perinatal conditions can lead to developmental programming of cardiovascular diseases. Prematurely born infants are often exposed to high oxygen levels, which in animal models has been associated with endothelial dysfunction, hypertension, and cardiac remodeling during adulthood. Here we found that adult mice that have been transiently exposed to O2 after birth show defective neovasculariation after hindlimb ischemia, as demonstrated by impaired blood flow recovery, reduced vascular density in ischemic muscles and increased tissue damages. Ischemic muscles isolated from mice exposed to O2 after birth exhibit increased oxidative stress levels and reduced expression of superoxide dismutase 1 (SOD1) and vascular endothelial growth factor (VEGF). Pro-angiogenic cells (PACs) have been shown to have an important role for postnatal neovascularisation. We found that neonatal exposure to O2 is associated with reduced number of PACs in adults. Moreover, the angiogenic activities of both PACs and mature mouse aortic endothelial cells (MAECs) are significantly impaired in mice exposed to hyperoxia after birth. Our results indicate that neonatal exposure to high oxygen levels leads to impaired ischemia-induced neovascularization during adulthood. The mechanism involves deleterious effects on oxidative stress levels and angiogenic signals in ischemic muscles, together with dysfunctional activities of PACs and mature endothelial cells.

MicroRNA-150 Modulates Ischemia-Induced Neovascularization in Atherosclerotic Conditions.

OBJECTIVE: Hypercholesterolemia is an atherosclerotic condition that is associated with impaired neovascularization in response to ischemia. This study sought to define the role of microRNAs in that pathophysiology. APPROACH AND RESULTS: Next-generation sequencing and quantitative reverse transcription polymerase chain reaction analyses identified miR-150 as a proangiogenic microRNA, which expression is significantly reduced in the ischemic muscles of hypercholesterolemic apolipoprotein E-deficient (ApoE-/-) mice, and in human umbilical vein endothelial cells exposed to oxidized low-density lipoprotein. Forced expression of miR-150 using a miR mimic could rescue oxidized low-density lipoprotein-mediated impairment of endothelial cell migration and tubule formation in vitro. In a mouse model of hindlimb ischemia, intramuscular injection of miR-150 mimic restored blood flow recuperation, vascular densities in ischemic muscles, and functional mobility in ApoE-/- mice. Treatment of ApoE-/- mice with miR-150 also increased the number and the activities of proangiogenic cells. miR-150 targets SRC kinase signaling inhibitor 1, an important regulator of Src (proto-oncogene tyrosine-protein kinase Src) activity. Here we found that hypercholesterolemia and oxidized low-density lipoprotein exposure are associated with increased SRC kinase signaling inhibitor 1 expression and decreased Src activity. However, treatment with miR-150 mimic reduces SRC kinase signaling inhibitor 1 expression and restores Src and downstream endothelial nitric oxide synthase and Akt (protein kinase B) activities both in vitro and in vivo. We also demonstrate the interrelation between miR-150 and SRC kinase signaling inhibitor 1 and their importance for endothelial cell angiogenic activities. CONCLUSIONS: Hypercholesterolemia is associated with reduced expression of miR-150, impaired Src signaling, and inefficient neovascularization in response to ischemia. Forced expression of miR-150 using a miR mimic could constitute a novel therapeutic strategy to improve ischemia-induced neovascularization in atherosclerotic conditions.

Reduced expression of let-7f activates TGF-ß/ALK5 pathway and leads to impaired ischaemia-induced neovascularization after cigarette smoke exposure.

This study sought to determine the potential role of microRNAs (miRNAs) in the detrimental effects of cigarette smoke on angiogenesis and neovascularization. Using large-scale miRNA profiling and qRT-PCR analyses, we identified let-7f as a pro-angiogenic miRNA which expression is significantly reduced in HUVECs treated with cigarette smoke extracts (CSE), and in the ischemic muscles of mice that are exposed to cigarette smoke (MES). In a mouse model of hindlimb ischaemia, intramuscular injection of let-7f mimic restored ischaemia-induced neovascularization in MES. Doppler flow ratios and capillary density in ischemic muscles were significantly improved in MES treated with let-7f mimic. Clinically, this was associated with reduced ambulatory impairment and hindlimb ischaemic damage. Treatment with let-7f mimic could also rescue pro-angiogenic cell (PAC) number and function (attachment, proliferation, migration) in MES. ALK5 (TGF-ßR1), an important modulator of angiogenesis, is a target of let-7f. Here we show that ALK5 is increased in HUVECs exposed to CSE and in the ischaemic muscles of MES. This is associated with a downstream activation of the anti-angiogenic factors SMAD2/3 and PAI-1. Importantly, treatment with let-7f mimic reduces the expression of ALK5, SMAD2/3 and PAI-1 both in vitro and in vivo. Moreover, let-7f overexpression or ALK5 inhibition can rescue angiogenesis in HUVECs exposed to CSE. Cigarette smoke exposure is associated with reduced expression of let-7f and activation of the anti-angiogenic TGF-ß/ALK5 pathway. Overexpression of let-7f using a miRNA mimic could constitute a novel therapeutic strategy to improve ischaemia-induced neovascularization in pathological conditions.

Direct renin inhibition with aliskiren improves ischemia-induced neovascularization: blood pressure-independent effect.

BACKGROUND: Renin is the rate limiting step for the activation of the renin-angiotensin-aldosterone system, which is linked to the development of endothelial dysfunction, hypertension and atherosclerosis. However, the specific role of renin during physiological responses to tissue ischemia is currently unknown. Aliskiren is the only direct renin inhibitor that is clinically used as an orally active antihypertensive drug. Here we tested the hypothesis that aliskiren might improve neovascularization in response to ischemia. METHODS AND RESULTS: At a dose that did not modulate blood pressure (10 mg/kg), aliskiren led to improved blood flow recovery after hindlimb ischemia in C57BL/6 mice (Doppler flow ratios 0.71 ± 0.07 vs. 0.55 ± 0.03; P < 0.05). In ischemic muscles, treatment with aliskiren was associated with a significant increase of vascular density, reduced oxidative stress levels and increased expression of VEGF and eNOS. Aliskiren treatment also significantly increased the number of bone marrow-derived endothelial progenitor cells (EPCs) after hindlimb ischemia. Moreover, the angiogenic properties of EPCs (migration, adhesion, integration into tubules) were significantly improved in mice treated with aliskiren. In vitro, aliskiren improves cellular migration and tubule formation in HUVECs. This is associated with an increased expression of nitric oxide (NO), and a significant reduction of oxidative stress levels. Importantly, the angiogenic properties of aliskiren in vitro and in vivo are completely abolished following treatment with the NOS inhibitor l-NAME. CONCLUSION: Direct renin inhibition with aliskiren leads to improved ischemia-induced neovascularization that is not dependant on blood pressure lowering. The mechanism involves beneficial effects of aliskiren on oxidative stress and NO angiogenic pathway, together with an increase in the number and the functional activities of EPCs.

Psychological stress impairs ischemia-induced neovascularization: Protective effect of fluoxetine.

BACKGROUND: Psychological stress (PS) has been associated with the development of cardiovascular diseases and adverse long-term outcomes after ischemic events. However, the precise mechanisms involved are not completely understood. Here we investigated the effect of PS on ischemia-induced neovascularization, and the potential therapeutic effect of fluoxetine in this condition. METHODS AND RESULTS: Balb/c mice were subjected or not to chronic restraint stress. After 3 weeks, hindlimb ischemia was surgically induced by femoral artery removal. We found that blood flow recovery was significantly impaired in mice exposed to PS compared to controls (Doppler flow ratio (DFR) 0.61 ± 0.07 vs. 0.80 ± 0.07, p < 0.05). At the microvascular level, capillary density was significantly reduced in ischemic muscles of mice exposed to PS (38 ± 1 vs. 74 ± 3 capillaries per field, p < 0.001). This correlated with increased oxidative stress levels and reduced expression of VEGF and VEGF signalling molecules (p44/p42 MAPK, Akt) in ischemic muscles. We found that the number of pro-angiogenic cells (PACs) was significantly reduced in mice exposed to PS. In addition, oxidative stress levels (DCF-DA, DHE) were increased in PACs isolated from mice exposed to PS, and this was associated with impaired PAC functional activities (migration, adhesion, and integration into tubules). Importantly, treatment of mice exposed to PS with the selective serotonin reuptake inhibitor (SSRI) fluoxetine improved all the angiogenic parameters, and completely rescued PS-induced impairment of neovascularization. CONCLUSION: PS impairs ischemia-induced neovascularization. Potential mechanisms involved include reduced activation of the VEGF pathway in ischemic tissues, increased oxidative stress levels and reduced number and functional activities of PACs. Our results suggest that fluoxetine may represent a novel therapeutic strategy to improve neovascularization and reduce ischemia in patients suffering from cardiovascular diseases and exposed to PS.

Elsibucol inhibits atherosclerosis following arterial injury: multifunctional effects on cholesterol levels, oxidative stress and inflammation.

BACKGROUND: Elsibucol is a metabolically stable derivative of probucol with antioxidant, anti-inflammatory and antiproliferative properties. Here we investigated the effect of elsibucol on the development of atherosclerosis following arterial injury in hypercholesterolemic rabbits. METHODS AND RESULTS: New Zealand White rabbits were fed a high cholesterol diet that was supplemented or not with 0.5% elsibucol, 1% elsibucol or 1% probucol. An angioplasty of the iliac artery was performed after 3 weeks of diet. We found that treatment with elsibucol significantly decreases blood total cholesterol, LDLc and triglyceride levels. This is associated with a significant 46% reduction of neointimal hyperplasia following arterial injury. Interestingly, the effect of elsibucol on cholesterol levels and neointimal formation appears to be more pronounced than that of probucol. In vitro, elsibucol reduces vascular smooth muscle cell proliferation without affecting cell viability. In vivo, treatment with elsibucol is associated with a significant reduction of cellular proliferation (PCNA immunostaining), oxidative stress (nitrotyrosine immunostaining), VCAM-1 expression and macrophage infiltration in injured arteries. Despite its potent effect on neointimal hyperplasia, elsibucol does not prevent endothelial healing (Evans blue staining) following arterial injury. CONCLUSIONS: In hypercholesterolemic animals, elsibucol inhibits atherosclerosis and preserves endothelial healing following arterial injury. The mechanisms involved include lowering of blood cholesterol levels together with a reduction of oxidative stress and inflammation in injured arteries.