Endothelin Receptor Blockade Improves Cerebral Blood Flow-Mediated Dilation in a Mouse Model of Alzheimer's Disease.

INTRODUCTION: Cerebral blood flow (CBF) is reduced in patients with Alzheimer's disease (AD). Flow-mediated dilation (FMD), which plays a key role in the regulation of blood flow, is attenuated by endothelin-1. We hypothesized that endothelin receptor blockade may improve CBF in AD. METHODS: We investigated cerebrovascular reactivity in a mouse model of AD (APP-PS1; 5-6-month-old male subjects). We assessed the in vivo response to normoxic hypercapnia and in vitro FMD in isolated cerebral and mesenteric resistance arteries before and after endothelin receptor blockade (bosentan). RESULTS: Normoxic hypercapnia increased basilar trunk blood flow velocity (+12.3 ± 2.4%; p = 0.006, n = 6) in wild-type (WT) mice but reduced blood flow in APP-PS1 mice (-11.4 ± 1.2%; p < 0.0001, n = 8). Bosentan (50 mg/kg, acute intraperitoneal injection) restored cerebrovascular reactivity in APP-PS1 mice (+10.2 ± 2.2%; p < 0.0001, n = 8) but had no effect in WT. FMD was reduced in the posterior cerebral artery of APP-PS1 compared to WT and was normalized by bosentan (1 µmol/L, 30 min, or 50 mg/kg/day for 28 days). FMD was similar in the mesenteric artery of APPS-PS1 and WT. CONCLUSION: APP-PS1 mice exhibited cerebrovascular endothelial dysfunction. Acute and chronic blockade of endothelin receptors restored endothelial vasomotor function, suggesting a promising therapeutic approach to restoring cerebral vasoreactivity in AD.

Synergistic actions between angiotensin-converting enzyme inhibitors and statins in atherosclerosis.

AIMS: Hypertension and hypercholesterolemia are independent risk factors for atherosclerotic cardiovascular disease (ASCVD) by acting directly on the endothelium and activating the renin-angiotensin aldosterone system (RAAS) and mevalonate pathways. This review examines how the severity and duration of these risk factors may influence the cardiovascular risk through a reciprocal interplay leading to oxidative stress and pro-inflammatory response. DATA SYNTHESIS: The review highlights the clinical evidence supporting the benefits of statins and angiotensin-converting enzyme (ACE) inhibitors for hypertension, lipid disorders and ASCVD management, both individually and combined, at all stages of the cardiovascular continuum. CONCLUSION: Drug strategies incorporating an ACE-inhibitor and a statin, and in particular perindopril and atorvastatin, have consistently demonstrated reductions in the rate of ASCVD events in patients with hypertension and lipid disorders, cementing their position as first-line therapies for the management of atherosclerosis complications.

Postischemic revascularization: from cellular and molecular mechanisms to clinical applications.

After the onset of ischemia, cardiac or skeletal muscle undergoes a continuum of molecular, cellular, and extracellular responses that determine the function and the remodeling of the ischemic tissue. Hypoxia-related pathways, immunoinflammatory balance, circulating or local vascular progenitor cells, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis, and collateral growth, which act in concert to establish a functional vascular network in ischemic zones. In patients with ischemic diseases, most of the cellular (mainly those involving bone marrow-derived cells and local stem/progenitor cells) and molecular mechanisms involved in the activation of vessel growth and vascular remodeling are markedly impaired by the deleterious microenvironment characterized by fibrosis, inflammation, hypoperfusion, and inhibition of endogenous angiogenic and regenerative programs. Furthermore, cardiovascular risk factors, including diabetes, hypercholesterolemia, hypertension, diabetes, and aging, constitute a deleterious macroenvironment that participates to the abrogation of postischemic revascularization and tissue regeneration observed in these patient populations. Thus stimulation of vessel growth and/or remodeling has emerged as a new therapeutic option in patients with ischemic diseases. Many strategies of therapeutic revascularization, based on the administration of growth factors or stem/progenitor cells from diverse sources, have been proposed and are currently tested in patients with peripheral arterial disease or cardiac diseases. This review provides an overview from our current knowledge regarding molecular and cellular mechanisms involved in postischemic revascularization, as well as advances in the clinical application of such strategies of therapeutic revascularization.

Mechanistic Investigations of Green mEos4b Reveal a Dynamic Long-Lived Dark State.

Green-to-red photoconvertible fluorescent proteins (PCFPs) are key players in advanced microscopy schemes such as photoactivated localization microscopy (PALM). Whereas photoconversion and red-state blinking in PCFPs have been studied intensively, their green-state photophysical behavior has received less attention. Yet dark states in green PCFPs can become strongly populated in PALM schemes and exert an indirect but considerable influence on the quality of data recorded in the red channel. Furthermore, green-state photoswitching in PCFPs can be used directly for PALM and has been engineered to design highly efficient reversibly switchable fluorescent proteins (RSFPs) amenable to various nanoscopy schemes. Here, we demonstrate that green mEos4b efficiently switches to a long-lived dark state through cis-trans isomerization of its chromophore, as do most RSFPs. However, by combining kinetic crystallography, molecular dynamics simulations, and Raman spectroscopy, we find that the dark state in green mEos4b is much more dynamic than that seen in switched-off green IrisFP, a biphotochromic PCFP engineered from the common EosFP parent. Our data suggest that H-bonding patterns maintained by the chromophore in green PCFPs and RSFPs in both their on- and off-states collectively control photoswitching quantum yields. The reduced number of H-bonds maintained by the dynamic dark chromophore in green mEos4b thus largely accounts for the observed lower switching contrast as compared to that of IrisFP. We also compare the long-lived dark states reached from green and red mEos4b, on the basis of their X-ray structures and Raman signatures. Altogether, these data provide a unifying picture of the complex photophysics of PCFPs and RSFPs.

Wall Shear Stress in the Feeding Native Conduit Arteries of Superficial Arteriovenous Malformations of the Lower Face is a Reliable Marker of Disease Progression.

PURPOSE: To assess the prognostic value of the wall shear stress (WSS) measured in the feeding native arteries upstream from facial superficial arteriovenous malformations (sAVMs). Reliable prognostic criteria are needed to distinguish progressive from stable sAVMs and thus support the indication for an aggressive or a conservative management to avoid severe facial disfigurement. MATERIALS AND METHODS: We prospectively included 25 patients with untreated facial sAVMs, 15 patients with surgically resected sAVMs and 15 controls. All had undergone Doppler ultrasound examination (DUS) with measurements of inner diameters, blood flow velocities, computation of blood flow and WSS of the feeding arteries. Based on the absence or presence of progression in clinical and imaging examinations 6 months after, we discriminated untreated patients as stable or progressive. RESULTS: WSS in the ipsilateral external carotid artery was higher in progressive compared to stable sAVMs (15.8 ±â€Š3.3dynes/cm² vs. 9.6 ±â€Š2.0dynes/cm², mean±SD, p < 0.0001) with a cut-off of 11.5dynes/cm² (sensitivity: 92 %, specificity: 92 %, AUC: 0.955, [95 %CI: 0.789-0.998], p = 0.0001). WSS in the ipsilateral facial artery was also higher in progressive compared to stable sAVMs (50.7 ±â€Š14.5dynes/cm² vs. 25.2 ±â€Š7.1dynes/cm², p < 0.0001) with a cut-off of 34.0dynes/cm² (sensitivity: 100 %, specificity: 92 %, AUC: 0.974, [95 %CI: 0.819-1.000], p = 0.0001). The hemodynamic data of operated patients were not different from those of the control group. CONCLUSION: WSS measured in the feeding arteries of an sAVM may be a simple reliable criterion to distinguish stable from progressive sAVMs. This value should be considered to guide the therapeutic strategy as well as the long-term follow-up of patients with facial sAVMs.

Peripheral post-ischemic vascular repair is impaired in a murine model of Alzheimer's disease.

The pathophysiology of sporadic Alzheimer's disease (AD) remains uncertain. Along with brain amyloid-ß (Aß) deposits and neurofibrillary tangles, cerebrovascular dysfunction is increasingly recognized as fundamental to the pathogenesis of AD. Using an experimental model of limb ischemia in transgenic APPPS1 mice, a model of AD (AD mice), we showed that microvascular impairment also extends to the peripheral vasculature in AD. At D70 following femoral ligation, we evidenced a significant decrease in cutaneous blood flow (- 29%, P < 0.001), collateral recruitment (- 24%, P < 0.001), capillary density (- 22%; P < 0.01) and arteriole density (- 28%; P < 0.05) in hind limbs of AD mice compared to control WT littermates. The reactivity of large arteries was not affected in AD mice, as confirmed by unaltered size, and vasoactive responses to pharmacological stimuli of the femoral artery. We identified blood as the only source of Aß in the hind limb; thus, circulating Aß is likely responsible for the impairment of peripheral vasculature repair mechanisms. The levels of the majority of pro-angiogenic mediators were not significantly modified in AD mice compared to WT mice, except for TGF-ß1 and PlGF-2, both of which are involved in vessel stabilization and decreased in AD mice (P = 0.025 and 0.019, respectively). Importantly, endothelin-1 levels were significantly increased, while those of nitric oxide were decreased in the hind limb of AD mice (P < 0.05). Our results suggest that vascular dysfunction is a systemic disorder in AD mice. Assessment of peripheral vascular function may therefore provide additional tools for early diagnosis and management of AD.

Interplay between the renin-angiotensin system, the canonical WNT/ß-catenin pathway and PPARγ in hypertension.

PURPOSE OF REVIEW: Heterogeneous causes can determinate hypertension. RECENT FINDINGS: The renin-angiotensin system (RAS) has a major role in the pathophysiology of blood pressure. Angiotensin II and aldosterone are overexpressed during hypertension and lead to hypertension development and its cardiovascular complications. In several tissues, the overactivation of the canonical WNT/ß-catenin pathway leads to inactivation of peroxisome proliferator-activated receptor gamma (PPARγ), while PPARγ stimulation induces a decrease of the canonical WNT/ß-catenin pathway. In hypertension, the WNT/ß-catenin pathway is upregulated, whereas PPARγ is decreased. The WNT/ß-catenin pathway and RAS regulate positively each other during hypertension, whereas PPARγ agonists can decrease the expression of both the WNT/ß-catenin pathway and RAS. We focus this review on the hypothesis of an opposite interplay between PPARγ and both the canonical WNT/ß-catenin pathway and RAS in regulating the molecular mechanism underlying hypertension. The interactions between PPARγ and the canonical WNT/ß-catenin pathway through the regulation of the renin-angiotensin system in hypertension may be an interesting way to better understand the actions and the effects of PPARγ agonists as antihypertensive drugs.

Theoretical estimation of redox potential of biological quinone cofactors.

Redox potentials are essential to understand biological cofactor reactivity and to predict their behavior in biological media. Experimental determination of redox potential in biological system is often difficult due to complexity of biological media but computational approaches can be used to estimate them. Nevertheless, the quality of the computational methodology remains a key issue to validate the results. Instead of looking to the best absolute results, we present here the calibration of theoretical redox potential for quinone derivatives in water coupling QM + MM or QM/MM scheme. Our approach allows using low computational cost theoretical level, ideal for long simulations in biological systems, and determination of the uncertainties linked to the calculations. © 2017 Wiley Periodicals, Inc.

Marked regional endothelial dysfunction in mottled skin area in patients with severe infections.

BACKGROUND: Mottling around the knee, reflecting a reduced skin blood flow, is predictive of mortality in patients with septic shock. However, the causative pathophysiology of mottling remains unknown. We hypothesized that the cutaneous hypoperfusion observed in the mottled area is related to regional endothelial dysfunction. METHODS: This was a prospective, observational study in a medical ICU in a tertiary teaching hospital. Consecutive adult patients with sepsis admitted to ICU were included. After resuscitation, endothelium-dependent vasodilation in the skin circulation was measured before and after iontophoresis of acetylcholine (Ach) in the forearm and the knee area. We analyzed the patterns of induced vasodilatation according to the presence or absence of mottling and vital status at 14 days. RESULTS: We evaluated 37 septic patients, including 11 without and 26 with septic shock. Overall 14-day mortality was 22%. Ten patients had mottling around the knee (10/37, 27%). In the knee area, the increased skin blood flow following iontophoresis of Ach was lower in patients with mottled skin as compared to patients without mottled skin (area under curve (AUC) 3280 (2643-6440) vs. 7980 (4233-19,707), both P < 0.05). In the forearm area, the increased skin blood flow following iontophoresis of Ach was similar in patients with and without mottled skin. Among patients with septic shock, the increased skin blood flow following iontophoresis of Ach in the knee area was significantly lower in non-survivors as compared to survivors at 14 days (AUC 3256 (2600-4426) vs. 7704 (4539-15,011), P < 0.01). In patients with septic shock, the increased skin blood flow in the forearm area following iontophoresis of Ach was similar in survivors and non-survivors at 14 days. CONCLUSION: Mottling is associated with regional endothelial dysfunction in patients with septic shock. Endothelial dysfunction in the knee skin area was more pronounced in non-survivors than in survivors.

Electron transfer, decoherence, and protein dynamics: insights from atomistic simulations.

Electron transfer in biological systems drives the processes of life. From cellular respiration to photosynthesis and enzymatic catalysis, electron transfers (ET) are chemical processes on which essential biological functions rely. Over the last 40 years, scientists have sought understanding of how these essential processes function in biology. One important breakthrough was the discovery that Marcus theory (MT) of electron transfer is applicable to biological systems. Chemists have experimentally collected both the reorganization energies (λ) and the driving forces (ΔG°), two parameters of Marcus theory, for a large variety of ET processes in proteins. At the same time, theoretical chemists have developed computational approaches that rely on molecular dynamics and quantum chemistry calculations to access numerical estimates of λ and ΔG°. Yet another crucial piece in determining the rate of an electron transfer is the electronic coupling between the initial and final electronic wave functions. This is an important prefactor in the nonadiabatic rate expression, since it reflects the probability that an electron tunnels from the electron donor to the acceptor through the intervening medium. The fact that a protein matrix supports electron tunneling much more efficiently than vacuum is now well documented, both experimentally and theoretically. Meanwhile, many chemists have provided examples of the rich physical chemistry that can be induced by protein dynamics. This Account describes our studies of the dynamical effects on electron tunneling. We present our analysis of two examples of natural biological systems through MD simulations and tunneling pathway analyses. Through these examples, we show that protein dynamics sustain efficient tunneling. Second, we introduce two time scales: τcoh and τFC. The former characterizes how fast the electronic coupling varies with nuclear vibrations (which cause dephasing). The latter reflects the time taken by the system to leave the crossing region. In the framework of open quantum systems, τFC is a short time approximation of the characteristic decoherence time of the electronic subsystem in interaction with its nuclear environment. The comparison of the respective values of τcoh and τFC allows us to probe the occurrence of non-Condon effects. We use ab initio MD simulations to analyze how decoherence appears in several biological cofactors. We conclude that we cannot account for its order of magnitude by considering only the atoms or bonds directly concerned with the transfer. Decoherence results from contributions from all atoms of the system appearing with a time delay that increases with the distance from the primarily concerned atoms or bonds. The delay and magnitude of the contributions depend on the chemical nature of the system. Finally, we present recent developments based on constrained DFT for efficient and accurate evaluations of the electronic coupling in ab initio MD simulations. These are promising methods to study the subtle fluctuations of the electronic coupling and the mechanisms of electronic decoherence in biological systems.

Characterization of nerve and microvessel damage and recovery in type 1 diabetic mice after permanent femoral artery ligation.

Neuropathy is the most common complication of the peripheral nervous system during the progression of diabetes. The pathophysiology is unclear but may involve microangiopathy, reduced endoneurial blood flow, and tissue ischemia. We used a mouse model of type 1 diabetes to study parallel alterations of nerves and microvessels following tissue ischemia. We designed an easily reproducible model of ischemic neuropathy induced by irreversible ligation of the femoral artery. We studied the evolution of behavioral function, epineurial and endoneurial vessel impairment, and large nerve myelinated fiber as well as small cutaneous unmyelinated fiber impairment for 1 month following the onset of ischemia. We observed a more severe hindlimb dysfunction and delayed recovery in diabetic animals. This was associated with reduced density of large arteries in the hindlimb and reduced sciatic nerve epineurial blood flow. A reduction in sciatic nerve endoneurial capillary density was also observed, associated with a reduction in small unmyelinated epidermal fiber number and large myelinated sciatic nerve fiber dysfunction. Moreover, vascular recovery was delayed, and nerve dysfunction was still present in diabetic animals at day 28. This easily reproducible model provides clear insight into the evolution over time of the impact of ischemia on nerve and microvessel homeostasis in the setting of diabetes. © 2015 Wiley Periodicals, Inc.

MicroRNA-21 coordinates human multipotent cardiovascular progenitors therapeutic potential.

Published clinical trials in patients with ischemic diseases show limited benefit of adult stem cell-based therapy, likely due to their restricted plasticity and commitment toward vascular cell lineage. We aim to uncover the potent regenerative ability of MesP1/stage-specific embryonic antigen 1 (SSEA-1)-expressing cardiovascular progenitors enriched from human embryonic stem cells (hESCs). Injection of only 10(4) hESC-derived SSEA-1(+) /MesP1(+) cells, or their progeny obtained after treatment with VEGF-A or PDGF-BB, was effective enough to enhance postischemic revascularization in immunodeficient mice with critical limb ischemia (CLI). However, the rate of incorporation of hESC-derived SSEA-1(+) /MesP1(+) cells and their derivatives in ischemic tissues was modest. Alternatively, these cells possessed a unique miR-21 signature that inhibited phosphotase and tensin homolog (PTEN) thereby activating HIF-1α and the systemic release of VEGF-A. Targeting miR-21 limited cell survival and inhibited their proangiogenic capacities both in the Matrigel model and in mice with CLI. We next assessed the impact of mR-21 in adult angiogenesis-promoting cells. We observed an impaired postischemic angiogenesis in miR-21-deficient mice. Notably, miR-21 was highly expressed in circulating and infiltrated monocytes where it targeted PTEN/HIF-1α/VEGF-A signaling and cell survival. As a result, miR-21-deficient mice displayed an impaired number of infiltrated monocytes and a defective angiogenic phenotype that could be partially restored by retransplantation of bone marrow-derived cells from wild-type littermates. hESC-derived SSEA-1(+) /MesP1(+) cells progenitor cells are powerful key integrators of therapeutic angiogenesis in ischemic milieu and miR-21 is instrumental in this process as well as in the orchestration of the biological activity of adult angiogenesis-promoting cells.

HIF-prolyl hydroxylase 2 inhibition enhances the efficiency of mesenchymal stem cell-based therapies for the treatment of critical limb ischemia.

Upregulation of hypoxia-inducible transcription factor-1α (HIF-1α), through prolyl-hydroxylase domain protein (PHD) inhibition, can be thought of as a master switch that coordinates the expression of a wide repertoire of genes involved in regulating vascular growth and remodeling. We aimed to unravel the effect of specific PHD2 isoform silencing in cell-based strategies designed to promote therapeutic revascularization in patients with critical limb ischemia (CLI). PHD2 mRNA levels were upregulated whereas that of HIF-1α were downregulated in blood cells from patients with CLI. We therefore assessed the putative beneficial effects of PHD2 silencing on human bone marrow-derived mesenchymal stem cells (hBM-MSC)-based therapy. PHD2 silencing enhanced hBM-MSC therapeutic effect in an experimental model of CLI in Nude mice, through an upregulation of HIF-1α and its target gene, VEGF-A. In addition, PHD2-transfected hBM-MSC displayed higher protection against apoptosis in vitro and increased rate of survival in the ischemic tissue, as assessed by Fluorescence Molecular Tomography. Cotransfection with HIF-1α or VEGF-A short interfering RNAs fully abrogated the beneficial effect of PHD2 silencing on the proangiogenic capacity of hBM-MSC. We finally investigated the effect of PHD2 inhibition on the revascularization potential of ischemic targeted tissues in the diabetic pathological context. Inhibition of PHD-2 with shRNAs increased postischemic neovascularization in diabetic mice with CLI. This increase was associated with an upregulation of proangiogenic and proarteriogenic factors and was blunted by concomitant silencing of HIF-1α. In conclusion, silencing of PHD2, by the transient upregulation of HIF-1α and its target gene VEGF-A, might improve the efficiency of hBM-MSC-based therapies.

Associations between dietary patterns and skin microcirculation in healthy subjects.

OBJECTIVE: Microvascular dysfunction is suggested to be a marker of common pathophysiological mechanisms in the development of insulin resistance, cardiovascular diseases, and type 2 diabetes mellitus. Given the established relationship of diet with the macrovascular disease, the aim of this study was to investigate for the first time the possible associations between dietary patterns and microcirculation. APPROACH AND RESULTS: Two hundred ninety-one healthy men and women selected from the Supplementation en Vitamines et Mineraux Antioxydants 2' cohort were assessed for anthropometric, nutritional, biochemical, and microcirculation parameters using finger skin capillaroscopy. Dietary intake was assessed cross-sectionally using a food frequency questionnaire, and principal component analysis was used to identify dietary patterns from 40 food groups. Six dietary patterns were identified. A dietary pattern characterized by increased consumption of vegetable oils, poultry, and fish and seafood was positively associated with both functional and anatomic capillary density after adjusting for confounders (ß=0.13, P=0.05 and ß=0.20, P=0.00, respectively). A second dietary pattern with increased consumption of sweets was inversely associated with functional and anatomic capillary density in all multivariate models (ß=-0.14, P=0.03 and ß=-0.17, P=0.01). There were no associations between any of the derived dietary patterns and capillary recruitment. CONCLUSIONS: In healthy subjects, a dietary pattern characterized by an increased consumption of vegetable oils, poultry, and fish and seafood and low consumption of sweets was associated with better microvascular function. Further prospective studies are needed to confirm the present association.

C/EBP homologous protein-10 (CHOP-10) limits postnatal neovascularization through control of endothelial nitric oxide synthase gene expression.

BACKGROUND: C/EBP homologous protein-10 (CHOP-10) is a novel developmentally regulated nuclear protein that emerges as a critical transcriptional integrator among pathways regulating differentiation, proliferation, and survival. In the present study, we analyzed the role of CHOP-10 in postnatal neovascularization. METHODS AND RESULTS: Ischemia was induced by right femoral artery ligation in wild-type and CHOP-10(-/-) mice. In capillary structure of skeletal muscle, CHOP-10 mRNA and protein levels were upregulated by ischemia and diabetes mellitus. Angiographic score, capillary density, and foot perfusion were increased in CHOP-10(-/-) mice compared with wild-type mice. This effect was associated with a reduction in apoptosis and an upregulation of endothelial nitric oxide synthase (eNOS) levels in ischemic legs of CHOP-10(-/-) mice compared with wild-type mice. In agreement with these results, eNOS mRNA and protein levels were significantly upregulated in CHOP-10 short interfering RNA-transfected human endothelial cells, whereas overexpression of CHOP-10 inhibited basal transcriptional activation of the eNOS promoter. Using a chromatin immunoprecipitation assay, we also showed that CHOP-10 was bound to the eNOS promoter. Interestingly, enhanced postischemic neovascularization in CHOP-10(-/-) mice was fully blunted in CHOP-10/eNOS double-knockout animals. Finally, we showed that induction of diabetes mellitus is associated with a marked upregulation of CHOP-10 that substantially inhibited postischemic neovascularization. CONCLUSIONS: This study identifies CHOP-10 as an important transcription factor modulating vessel formation and maturation.

Hepatic ischemia-reperfusion increases circulating bone marrow-derived progenitor cells and tumor growth in a mouse model of colorectal liver metastases.

BACKGROUND: Hepatic pedicle clamping is often required to reduce blood loss and transfusion during liver resection. However, the question remains whether use of hepatic pedicle clamping promotes tumor growth. Endothelial progenitor cells (EPCs) are mobilized from bone marrow in response to tissue ischemia, which allows neovascularization of ischemic tissue. It has been suggested that EPCs are involved in tumor progression. We hypothesized that hepatic ischemia reperfusion (I/R)-induced mobilization of EPCs could enhance growth of microscopic tumor, therefore promoting liver metastasis in a mouse model of colorectal cancer. MATERIALS AND METHODS: We used mouse models of hepatic I/R and hind limb ischemia. For comparison, we studied mice that underwent limb ischemia as positive controls of EPC mobilization. At day 0, we divided 40 mice into four groups: hepatic I/R, hind limb ischemia, combined hepatic I/R and hind limb ischemia, and control (sham midline incision laparotomy). At day 2, we induced liver metastasis in all mice by injecting CT-26 cells into the spleen. Time-dependent circulating EPCs were determined by flow cytometry. We evaluated liver metastasis and microvascular density on day 21. RESULTS: The number of circulating progenitor cells increased rapidly in the ischemic groups compared with the control group. Hepatic I/R significantly increased tumor outgrowth compared with the control group. Increased tumor growth was associated with enhanced CD31-positive microvascular density in liver tissue. CONCLUSIONS: Hepatic I/R leads to mobilization of bone marrow-derived EPCs and enhanced intra-hepatic angiogenesis, which is associated with increased tumor burden in an animal model of colorectal liver metastasis.

Sympathetic nervous system regulates bone marrow-derived cell egress through endothelial nitric oxide synthase activation: role in postischemic tissue remodeling.

OBJECTIVE: Catecholamines have been shown to control bone marrow (BM)-derived cell egress, yet the cellular and molecular mechanisms involved in this effect and their subsequent participation to postischemic vessel growth are poorly understood. METHODS AND RESULTS: Tyrosine hydroxylase mRNA levels, as well as dopamine (DA) and norepinephrine (NE) contents, were increased in the ischemic BM of mice with right femoral artery ligation. Angiographic score, capillary density, and arteriole number were markedly increased by treatments with DA (IP, 50 mg/kg, 5 days) or NE (IP, 2.5 mg/kg, 5 days). Using chimeric mice lethally irradiated and transplanted with BM-derived cells from green fluorescent protein mice, we showed that DA and NE enhanced by 70% (P<0.01) and 62% (P<0.001), respectively, the number of green fluorescent protein-positive BM-derived cells in ischemic tissue and promoted their ability to differentiate into cells with endothelial and inflammatory phenotypes. Similarly, both DA and NE increased the in vitro differentiation of cultured BM-derived cells into cells with endothelial phenotype. This increase was blunted by the nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester. DA and NE also upregulated the number of CD45-positive cells in blood 3 days after ischemia and that of macrophages in ischemic tissue 21 days after ischemia. Of interest, DA and NE increased BM endothelial nitric oxide synthase (eNOS) mRNA levels and were unable to promote BM-derived cell mobilization in chimeric eNOS-deficient mice lethally irradiated and transplanted with BM-derived cells from wild-type animals. Furthermore, administration of a ß2 adrenergic agonist (clenbuterol, IP, 2 mg/kg, 5 days) and that of a dopaminergic D1/D5 receptor agonist (SKF-38393, IP, 2.5 mg/kg, 5 days) also enhanced BM-derived cell mobilization and subsequently postischemic vessel growth. CONCLUSION These results unravel, for the first time, a major role for the sympathetic nervous system in BM-derived cell egress through stromal eNOS activation.

The chemokine decoy receptor D6 prevents excessive inflammation and adverse ventricular remodeling after myocardial infarction.

OBJECTIVE: Leukocyte infiltration in ischemic areas is a hallmark of myocardial infarction, and overwhelming infiltration of innate immune cells has been shown to promote adverse remodeling and cardiac rupture. Recruitment of inflammatory cells in the ischemic heart depends highly on the family of CC-chemokines and their receptors. Here, we hypothesized that the chemokine decoy receptor D6, which specifically binds and scavenges inflammatory CC-chemokines, might limit inflammation and adverse cardiac remodeling after infarction. METHODS AND RESULTS: D6 was expressed in human and murine infarcted myocardium. In a murine model of myocardial infarction, D6 deficiency led to increased chemokine (C-C motif) ligand 2 and chemokine (C-C motif) ligand 3 levels in the ischemic heart. D6-deficient (D6(-/-)) infarcts displayed increased infiltration of pathogenic neutrophils and Ly6Chi monocytes, associated with strong matrix metalloproteinase-9 and matrix metalloproteinase-2 activities in the ischemic heart. D6(-/-) mice were cardiac rupture prone after myocardial infarction, and functional analysis revealed that D6(-/-) hearts had features of adverse remodeling with left ventricle dilation and reduced ejection fraction. Bone marrow chimera experiments showed that leukocyte-borne D6 had no role in this setting, and that leukocyte-specific chemokine (C-C motif) receptor 2 deficiency rescued the adverse phenotype observed in D6(-/-) mice. CONCLUSIONS: We show for the first time that the chemokine decoy receptor D6 limits CC-chemokine-dependent pathogenic inflammation and is required for adequate cardiac remodeling after myocardial infarction.

VEGF (Vascular Endothelial Growth Factor) Inhibition and Hypertension: Does Microvascular Rarefaction Play a Role?

Drugs acting by inhibition of the angiogenic action of VEGF (vascular endothelial growth factor) have become major instruments in the treatment of cancer. The downside of their favorable effects in cancer treatment is their frequent cardiovascular side effects. The most consistent finding thus far on the cardiovascular side effects of VEGF inhibitors is the high incidence of hypertension. In this short review, we discuss the evidence that hypertension occurring during VEGF inhibitor treatment is caused by microvascular rarefaction. After a review of the role of VEGF in microvascular growth and differentiation, we present evidence from studies in experimental models of hypertension as well as clinical studies on the microvascular network changes during and after VEGF inhibitor treatment.