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OBJECTIVE - The continuous endothelium of skeletal muscle (SkM) capillaries regulates insulin's access to skeletal myocytes. Whether impaired transendothelial insulin transport (EIT) contributes to SkM insulin resistance (IR), however, is unknown.
METHODS - Male and female C57/Bl6 mice were fed either chow or a high-fat diet for 16 weeks. Intravital microscopy was used to measure EIT in SkM capillaries, electron microscopy to assess endothelial ultrastructure, and glucose tracers to measure indices of glucose metabolism.
RESULTS - Diet-induced obesity (DIO) male mice were found to have a ~15% reduction in EIT compared with lean mice. Impaired EIT was associated with a 45% reduction in endothelial vesicles. Despite impaired EIT, hyperinsulinemia sustained delivery of insulin to the interstitial space in DIO male mice. Even with sustained interstitial insulin delivery, DIO male mice still showed SkM IR indicating severe myocellular IR in this model. Interestingly, there was no difference in EIT, endothelial ultrastructure, or SkM insulin sensitivity between lean female mice and female mice fed a high-fat diet.
CONCLUSIONS - These results suggest that, in male mice, obesity results in ultrastructural alterations to the capillary endothelium that delay EIT. Nonetheless, the myocyte appears to exceed the endothelium as a contributor to SkM IR in DIO male mice.
© 2020 The Authors. Obesity published by Wiley Periodicals, Inc. on behalf of The Obesity Society (TOS).
OBJECTIVE - Insulin resistance is associated with increased lipolysis and elevated concentrations of free fatty acids (FFA), which in turn contribute to impaired vascular function. It was hypothesized that lowering FFA with acipimox, a nicotinic acid derivative that impairs FFA efflux, would improve endothelial function, measured by flow-mediated dilation (FMD), in individuals with metabolic syndrome.
METHODS - A total of 18 participants with metabolic syndrome and 17 healthy controls were enrolled and treated with acipimox 250 mg orally every 6 hours or placebo for 7 days in a randomized, double-blind, crossover trial.
RESULTS - Acipimox reduced FFA concentrations among individuals with metabolic syndrome to near normal levels (P = 0.01), but there was no change among healthy controls (P = 0.17). Acipimox did not improve endothelial-dependent FMD in either group (metabolic syndrome: P = 0.42; healthy controls: P = 0.16), although endothelial-independent nitroglycerin-mediated dilation among those with metabolic syndrome tended to increase (20.3%, P = 0.06). There were no changes in blood lipids or markers of inflammation following therapy. There was minimal correlation between change in FMD and baseline measures of BMI ( ρ = -0.09) or waist circumference ( ρ = -0.15).
CONCLUSIONS - In groups with normal or elevated baseline FFA, short-term reductions do not improve endothelial function assessed by FMD.
© 2019 The Obesity Society.
OBJECTIVES - Cardiopulmonary bypass-induced endothelial dysfunction has been inferred by changes in pulmonary vascular resistance, alterations in circulating biomarkers, and postoperative capillary leak. Endothelial-dependent vasomotor dysfunction of the systemic vasculature has never been quantified in this setting. The objective of the present study was to quantify acute effects of cardiopulmonary bypass on endothelial vasomotor control and attempt to correlate these effects with postoperative cytokines, tissue edema, and clinical outcomes in infants.
DESIGN - Single-center prospective observational cohort pilot study.
SETTING - Pediatric cardiac ICU at a tertiary children's hospital.
PATIENTS - Children less than 1 year old requiring cardiopulmonary bypass for repair of a congenital heart lesion.
INTERVENTION - None.
MEASUREMENTS AND MAIN RESULTS - Laser Doppler perfusion monitoring was coupled with local iontophoresis of acetylcholine (endothelium-dependent vasodilator) or sodium nitroprusside (endothelium-independent vasodilator) to quantify endothelial-dependent vasomotor function in the cutaneous microcirculation. Measurements were obtained preoperatively, 2-4 hours, and 24 hours after separation from cardiopulmonary bypass. Fifteen patients completed all laser Doppler perfusion monitor (Perimed, Järfälla, Sweden) measurements. Comparing prebypass with 2-4 hours postbypass responses, there was a decrease in both peak perfusion (p = 0.0006) and area under the dose-response curve (p = 0.005) following acetylcholine, but no change in responses to sodium nitroprusside. Twenty-four hours after bypass responsiveness to acetylcholine improved, but typically remained depressed from baseline. Conserved endothelial function was associated with higher urine output during the first 48 postoperative hours (R = 0.43; p = 0.008).
CONCLUSIONS - Cutaneous endothelial dysfunction is present in infants immediately following cardiopulmonary bypass and recovers significantly in some patients within 24 hours postoperatively. Confirmation of an association between persistent endothelial-dependent vasomotor dysfunction and decreased urine output could have important clinical implications. Ongoing research will explore the pattern of endothelial-dependent vasomotor dysfunction after cardiopulmonary bypass and its relationship with biochemical markers of inflammation and clinical outcomes.
OBJECTIVE - Natriuretic peptides (NPs) are hormones with cardioprotective effects. NP levels vary by race; however, the pathophysiological consequences of lower NP levels are not well understood. We aimed to quantify the association between NPs and endothelial function as measured by flow-mediated dilation (FMD) and the contribution of NP levels to racial differences in endothelial function.
METHODS - In this cross-sectional study of 2938 Multi-Ethnic Study of Atherosclerosis participants (34% Caucasian, 20% African-American, 20% Asian-American and 26% Hispanic) without cardiovascular disease at baseline, multivariable linear regression models were used to examine the association between serum N-terminal pro-B-type NP (NT-proBNP) and natural log-transformed FMD. We also tested whether NT-proBNP mediated the relationship between race and FMD using the product of coefficients method.
RESULTS - Among African-American and Chinese-American individuals, lower NT-proBNP levels were associated with lower FMD, β=0.06 (95% CI: 0.03 to 0.09; p<0.001) and β=0.06 (95% CI: 0.02 to 0.09; p=0.002), respectively. Non-significant associations between NT-proBNP and FMD were found in Hispanic and Caucasian individuals. In multivariable models, endothelial function differed by race, with African-American individuals having the lowest FMD compared with Caucasians, p<0.001. Racial differences in FMD among African-Americans and Chinese-Americans were mediated in part by NT-proBNP levels (African-Americans, mediation effect: -0.03(95% CI: -0.05 to -0.01); Chinese-Americans, mediation effect: -0.03(95% CI: -0.05 to -0.01)).
CONCLUSIONS - Lower NP levels are associated with worse endothelial function among African-Americans and Chinese-Americans. A relative NP deficiency in some racial/ethnic groups may contribute to differences in vascular function.
© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.
BACKGROUND - Vascular dysfunction is commonly seen during severe viral infections. Endothelial nitric oxide synthase (eNOS), has been postulated to play an important role in regulating vascular homeostasis as well as propagation of the inflammatory reaction. We hypothesized that the loss of eNOS would negatively impact toll-like receptor 3 (TLR3) signaling and worsen vascular function to viral challenge.
METHODS - Human microvascular endothelial cells (HMVECs) were exposed to either control or eNOS siRNA and then treated with Poly I:C, a TLR3 agonist and mimicker of dsRNA viruses. Cells were assessed for protein-protein associations, cytokine and chemokine analysis as well as transendothelial electrical resistance (TEER) as a surrogate of permeability.
RESULTS - HMVECs that had reduced eNOS expression had a significantly elevated increase in IL-6, IL-8 and IP-10 production after Poly I:C. In addition, the knockdown of eNOS enhanced the change in TEER after Poly I:C stimulation. Western blot analysis showed enhanced phosphorylation of p38 in sieNOS treated cells with Poly I:C compared to siControl cells. Proximity ligation assays further demonstrated direct eNOS-p38 protein-protein interactions. The addition of the p38 inhibitor, SB203580, in eNOS knockdown cells reduced both cytokine production after Poly I:C, and as well as mitigated the reduction in TEER, suggesting a direct link between eNOS and p38 in TLR3 signaling.
CONCLUSIONS - These results suggest that reduction of eNOS increases TLR3-mediated inflammation in human endothelial cells in a p38-dependent manner. This finding has important implications for understanding the pathogenesis of severe viral infections and the associated vascular dysfunction.
There is a profound need for functional, biomimetic in vitro tissue constructs of the human blood-brain barrier and neurovascular unit (NVU) to model diseases and identify therapeutic interventions. Here, we show that induced pluripotent stem cell (iPSC)-derived human brain microvascular endothelial cells (BMECs) exhibit robust barrier functionality when cultured in 3D channels within gelatin hydrogels. We determined that BMECs cultured in 3D under perfusion conditions were 10-100 times less permeable to sodium fluorescein, 3 kDa dextran, and albumin relative to human umbilical vein endothelial cell and human dermal microvascular endothelial cell controls, and the BMECs maintained barrier function for up to 21 days. Analysis of cell-cell junctions revealed expression patterns supporting barrier formation. Finally, efflux transporter activity was maintained over 3 weeks of perfused culture. Taken together, this work lays the foundation for development of a representative 3D in vitro model of the human NVU constructed from iPSCs.
Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.
BACKGROUND AND AIMS - Cardiovascular disease (CVD) is the leading cause of death in chronic kidney disease (CKD) patients, however, the underlying mechanisms that link CKD and CVD are not fully understood and limited treatment options exist in this high-risk population. microRNAs (miRNA) are critical regulators of gene expression for many biological processes in atherosclerosis, including endothelial dysfunction and inflammation. We hypothesized that renal injury-induced endothelial miRNAs promote atherosclerosis. Here, we demonstrate that dual inhibition of endothelial miRNAs inhibits atherosclerosis in the setting of renal injury.
METHODS - Aortic endothelial miRNAs were analyzed in apolipoprotein E-deficient (Apoe) mice with renal damage (5/6 nephrectomy, 5/6Nx) by real-time PCR. Endothelial miR-92a-3p and miR-489-3p were inhibited by locked-nucleic acid (LNA) miRNA inhibitors complexed to HDL.
RESULTS - Renal injury significantly increased endothelial miR-92a-3p levels in Apoe;5/6Nx mice. Dual inhibition of miR-92a-3p and miR-489-3p in Apoe;5/6Nx with a single injection of HDL + LNA inhibitors significantly reduced atherosclerotic lesion area by 28.6% compared to HDL + LNA scramble (LNA-Scr) controls. To examine the impact of dual LNA treatment on aortic endothelial gene expression, total RNA sequencing was completed, and multiple putative target genes and pathways were identified to be significantly altered, including the STAT3 immune response pathway. Among the differentially expressed genes, Tgfb2 and Fam220a were identified as putative targets of miR-489-3p and miR-92a-3p, respectively. Both Tgfb2 and Fam220a were significantly increased in aortic endothelium after miRNA inhibition in vivo compared to HDL + LNA-Scr controls. Furthermore, Tgfb2 and Fam220a were validated with gene reporter assays as direct targets of miR-489-3p and miR-92a-3p, respectively. In human coronary artery endothelial cells, over-expression and inhibition of miR-92a-3p decreased and increased FAM220A expression, respectively. Moreover, miR-92a-3p overexpression increased STAT3 phosphorylation, likely through direct regulation of FAM220A, a negative regulator of STAT3 phosphorylation.
CONCLUSIONS - These results support endothelial miRNAs as therapeutic targets and dual miRNA inhibition as viable strategy to reduce CKD-associated atherosclerosis.
Copyright © 2019. Published by Elsevier B.V.
The third-generation tyrosine kinase inhibitor (TKI) ponatinib has been associated with high rates of acute ischemic events. The pathophysiology responsible for these events is unknown. We hypothesized that ponatinib produces an endothelial angiopathy involving excessive endothelial-associated von Willebrand factor (VWF) and secondary platelet adhesion. In wild-type mice and ApoE mice on a Western diet, ultrasound molecular imaging of the thoracic aorta for VWF A1-domain and glycoprotein-Ibα was performed to quantify endothelial-associated VWF and platelet adhesion. After treatment of wild-type mice for 7 days, aortic molecular signal for endothelial-associated VWF and platelet adhesion were five- to sixfold higher in ponatinib vs sham therapy ( < .001), whereas dasatinib had no effect. In ApoE mice, aortic VWF and platelet signals were two- to fourfold higher for ponatinib-treated compared with sham-treated mice ( < .05) and were significantly higher than in treated wild-type mice ( < .05). Platelet and VWF signals in ponatinib-treated mice were significantly reduced by -acetylcysteine and completely eliminated by recombinant ADAMTS13. Ponatinib produced segmental left ventricular wall motion abnormalities in 33% of wild-type and 45% of ApoE mice and corresponding patchy perfusion defects, yet coronary arteries were normal on angiography. Instead, a global microvascular angiopathy was detected by immunohistochemistry and by intravital microscopy observation of platelet aggregates and nets associated with endothelial cells and leukocytes. Our findings reveal a new form of vascular toxicity for the TKI ponatinib that involves VWF-mediated platelet adhesion and a secondary microvascular angiopathy that produces ischemic wall motion abnormalities. These processes can be mitigated by interventions known to reduce VWF multimer size.
© 2019 by The American Society of Hematology.
Tobacco smoking is a major risk factor for cardiovascular disease and hypertension. It is associated with the oxidative stress and induces metabolic reprogramming, altering mitochondrial function. We hypothesized that cigarette smoke induces cardiovascular mitochondrial oxidative stress, which contributes to endothelial dysfunction and hypertension. To test this hypothesis, we studied whether the scavenging of mitochondrial HO in transgenic mice expressing mitochondria-targeted catalase (mCAT) attenuates the development of cigarette smoke/angiotensin II-induced mitochondrial oxidative stress and hypertension compared with wild-type mice. Two weeks of exposure of wild-type mice with cigarette smoke increased systolic blood pressure by 17 mmHg, which was similar to the effect of a subpresssor dose of angiotensin II (0.2 mg·kg·day), leading to a moderate increase to the prehypertensive level. Cigarette smoke exposure and a low dose of angiotensin II cooperatively induced severe hypertension in wild-type mice, but the scavenging of mitochondrial HO in mCAT mice completely prevented the development of hypertension. Cigarette smoke and angiotensin II cooperatively induced oxidation of cardiolipin (a specific biomarker of mitochondrial oxidative stress) in wild-type mice, which was abolished in mCAT mice. Cigarette smoke and angiotensin II impaired endothelium-dependent relaxation and induced superoxide overproduction, which was diminished in mCAT mice. To mimic the tobacco smoke exposure, we used cigarette smoke condensate, which induced mitochondrial superoxide overproduction and reduced endothelial nitric oxide (a hallmark of endothelial dysfunction in hypertension). Western blot experiments indicated that tobacco smoke and angiotensin II reduce the mitochondrial deacetylase sirtuin-3 level and cause hyperacetylation of a key mitochondrial antioxidant, SOD2, which promotes mitochondrial oxidative stress. NEW & NOTEWORTHY This work demonstrates tobacco smoking-induced mitochondrial oxidative stress, which contributes to endothelial dysfunction and development of hypertension. We suggest that the targeting of mitochondrial oxidative stress can be beneficial for treatment of pathological conditions associated with tobacco smoking, such as endothelial dysfunction, hypertension, and cardiovascular diseases.
Intimal stiffening has been linked with increased vascular permeability and leukocyte transmigration, hallmarks of atherosclerosis. However, recent evidence indicates age-related intimal stiffening is not uniform but rather characterized by increased point-to-point heterogeneity in subendothelial matrix stiffness, the impact of which is much less understood. To investigate the impact of spatially heterogeneous matrix rigidity on endothelial monolayer integrity, we develop a micropillar model to introduce closely-spaced, step-changes in substrate rigidity and compare endothelial monolayer phenotype to rigidity-matched, uniformly stiff and compliant substrates. We found equivalent disruption of adherens junctions within monolayers on step-rigidity and uniformly stiff substrates relative to uniformly compliant substrates. Similarly, monolayers cultured on step-rigidity substrates exhibited equivalent percentages of leukocyte transmigration to monolayers on rigidity-matched, uniformly stiff substrates. Adherens junction tension and focal adhesion density, but not size, increased within monolayers on step-rigidity and uniformly stiff substrates compared to more compliant substrates suggesting that elevated tension is disrupting adherens junction integrity. Leukocyte transmigration frequency and time, focal adhesion size, and focal adhesion density did not differ between stiff and compliant sub-regions of step-rigidity substrates. Overall, our results suggest that endothelial monolayers exposed to mechanically heterogeneous substrates adopt the phenotype associated with the stiffer matrix, indicating that spatial heterogeneities in intimal stiffness observed with age could disrupt endothelial barrier integrity and contribute to atherogenesis.