AGPAT3 deficiency impairs adipocyte differentiation and leads to a lean phenotype in mice.

Acylglycerophosphate acyltransferases (AGPATs) catalyze the de novo formation of phosphatidic acid to synthesize glycerophospholipids and triglycerides. AGPATs demonstrate unique physiological roles despite a similar biochemical function. AGPAT3 is highly expressed in the testis, kidney, and liver, with intermediate expression in adipose tissue. Loss of AGPAT3 is associated with reproductive abnormalities and visual dysfunction. However, the role of AGPAT3 in adipose tissue and whole body metabolism has not been investigated. We found that male Agpat3 knockout (KO) mice exhibited reduced body weights with decreased white and brown adipose tissue mass. Such changes were less pronounced in the female Agpat3-KO mice. Agpat3-KO mice have reduced plasma insulin growth factor 1 (IGF1) and insulin levels and diminished circulating lipid metabolites. They manifested intact glucose homeostasis and insulin sensitivity despite a lean phenotype. Agpat3-KO mice maintained an energy balance with normal food intake, energy expenditure, and physical activity, except for increased water intake. Their adaptive thermogenesis was also normal despite reduced brown adipose mass and triglyceride content. Mechanistically, Agpat3 was elevated during mouse and human adipogenesis and enriched in adipocytes. Agpat3-knockdown 3T3-L1 cells and Agpat3-deficient mouse embryonic fibroblasts (MEFs) have impaired adipogenesis in vitro. Interestingly, pioglitazone treatment rescued the adipogenic deficiency in Agpat3-deficient cells. We conclude that AGPAT3 regulates adipogenesis and adipose development. It is possible that adipogenic impairment in Agpat3-deficient cells potentially leads to reduced adipose mass. Findings from this work support the unique role of AGPAT3 in adipose tissue.NEW & NOTEWORTHY AGPAT3 deficiency results in male-specific growth retardation. It reduces adipose tissue mass but does not significantly impact glucose homeostasis or energy balance, except for influencing water intake in mice. Like AGPAT2, AGPAT3 is upregulated during adipogenesis, potentially by peroxisome proliferator-activated receptor gamma (PPARγ). Loss of AGPAT3 impairs adipocyte differentiation, which could be rescued by pioglitazone. Overall, AGPAT3 plays a significant role in regulating adipose tissue mass, partially involving its influence on adipocyte differentiation.

Adenosine kinase inhibition enhances microvascular dilator function and improves left ventricle diastolic dysfunction.

OBJECTIVE: Inhibition of adenosine kinase (ADK), via augmenting endogenous adenosine levels exerts cardiovascular protection. We tested the hypothesis that ADK inhibition improves microvascular dilator and left ventricle (LV) contractile function under metabolic or hemodynamic stress. METHODS AND RESULTS: In Obese diabetic Zucker fatty/spontaneously hypertensive heart failure F1 hybrid rats, treatment with the selective ADK inhibitor, ABT-702 (1.5 mg/kg, intraperitoneal injections for 8-week) restored acetylcholine-, sodium nitroprusside-, and adenosine-induced dilations in isolated coronary arterioles, an effect that was accompanied by normalized end-diastolic pressure (in mm Hg, Lean: 3.4 ± 0.6, Obese: 17.6 ± 4.2, Obese + ABT: 6.6 ± 1.4) and LV relaxation constant, Tau (in ms, Lean: 6.9 ± 1.5, Obese: 13.9 ± 1.7, Obese + ABT: 6.0 ± 1.1). Mice with vascular endothelium selective ADK deletion (ADKVEC KO) exhibited an enhanced dilation to acetylcholine in isolated gracilis muscle (lgEC50 WT: -8.2 ± 0.1, ADKVEC KO: -8.8 ± 0.1, P < .05) and mesenteric arterioles (lgEC50 WT: -7.4 ± 0.2, ADKVEC KO: -8.1 ± 1.2, P < .05) when compared to wild-type (WT) mice, whereas relaxation of the femoral artery and aorta (lgEC50 WT: -7.03 ± 0.6, ADKVEC KO: -7.05 ± 0.8) was similar in the two groups. Wild-type mice progressively developed LV systolic and diastolic dysfunction when they underwent transverse aortic constriction surgery, whereas ADKVEC -KO mice displayed a lesser degree in decline of LV function. CONCLUSIONS: Our results indicate that ADK inhibition selectively enhances microvascular vasodilator function, whereby it improves LV perfusion and LV contractile function under metabolic and hemodynamic stress.

Vasodilator dysfunction and oligodendrocyte dysmaturation in aging white matter.

OBJECTIVE: Microvascular brain injury (mVBI) is a common pathological correlate of vascular contributions to cognitive impairment and dementia (VCID) that leads to white matter (WM) injury (WMI). VCID appears to arise from chronic recurrent white matter ischemia that triggers oxidative stress and an increase in total oligodendrocyte lineage cells. We hypothesized that mVBI involves vasodilator dysfunction of white matter penetrating arterioles and aberrant oligodendrocyte progenitor cell (OPC) responses to WMI. METHODS: We analyzed cases of mVBI with low Alzheimer's disease neuropathological change in prefrontal cortex WM from rapid autopsies in a population-based cohort where VCID frequently occurs. Arteriolar vasodilator function was quantified by videomicroscopy. OPC maturation was quantified using lineage specific markers. RESULTS: Acetylcholine-mediated arteriolar dilation in mVBI was significantly reduced in WM penetrators relative to pial arterioles. Astrogliosis-defined WMI was positively associated with increased OPCs and was negatively associated with decreased mature oligodendrocytes. INTERPRETATION: Selectively impaired vasodilator function of WM penetrating arterioles in mVBI occurs in association with aberrant differentiation of OPCs in WMI, which supports that myelination disturbances in VCID are related to disrupted maturation of myelinating oligodendrocytes. Ann Neurol 2018;83:142-152.

Akt2 (Protein Kinase B Beta) Stabilizes ATP7A, a Copper Transporter for Extracellular Superoxide Dismutase, in Vascular Smooth Muscle: Novel Mechanism to Limit Endothelial Dysfunction in Type 2 Diabetes Mellitus.

OBJECTIVE: Copper transporter ATP7A (copper-transporting/ATPase) is required for full activation of SOD3 (extracellular superoxide dismutase), which is secreted from vascular smooth muscle cells (VSMCs) and anchors to endothelial cell surface to preserve endothelial function by scavenging extracellular superoxide. We reported that ATP7A protein expression and SOD3 activity are decreased in insulin-deficient type 1 diabetes mellitus vessels, thereby, inducing superoxide-mediated endothelial dysfunction, which are rescued by insulin treatment. However, it is unknown regarding the mechanism by which insulin increases ATP7A expression in VSMCs and whether ATP7A downregulation is observed in T2DM (type2 diabetes mellitus) mice and human in which insulin-Akt (protein kinase B) pathway is selectively impaired. APPROACH AND RESULTS: Here we show that ATP7A protein is markedly downregulated in vessels isolated from T2DM patients, as well as those from high-fat diet-induced or db/db T2DM mice. Akt2 (protein kinase B beta) activated by insulin promotes ATP7A stabilization via preventing ubiquitination/degradation as well as translocation to plasma membrane in VSMCs, which contributes to activation of SOD3 that protects against T2DM-induced endothelial dysfunction. Downregulation of ATP7A in T2DM vessels is restored by constitutive active Akt or PTP1B-/- (protein-tyrosine phosphatase 1B-deficient) T2DM mice, which enhance insulin-Akt signaling. Immunoprecipitation, in vitro kinase assay, and mass spectrometry analysis reveal that insulin stimulates Akt2 binding to ATP7A to induce phosphorylation at Ser1424/1463/1466. Furthermore, SOD3 activity is reduced in Akt2-/- vessels or VSMCs, which is rescued by ATP7A overexpression. CONCLUSION: Akt2 plays a critical role in ATP7A protein stabilization and translocation to plasma membrane in VSMCs, which contributes to full activation of vascular SOD3 that protects against endothelial dysfunction in T2DM.

Role of growth hormone-releasing hormone in dyslipidemia associated with experimental type 1 diabetes.

Dyslipidemia associated with triglyceride-rich lipoproteins (TRLs) represents an important residual risk factor for cardiovascular and chronic kidney disease in patients with type 1 diabetes (T1D). Levels of growth hormone (GH) are elevated in T1D, which aggravates both hyperglycemia and dyslipidemia. The hypothalamic growth hormone-releasing hormone (GHRH) regulates the release of GH by the pituitary but also exerts separate actions on peripheral GHRH receptors, the functional role of which remains elusive in T1D. In a rat model of streptozotocin (STZ)-induced T1D, GHRH receptor expression was found to be up-regulated in the distal small intestine, a tissue involved in chylomicron synthesis. Treatment of T1D rats with a GHRH antagonist, MIA-602, at a dose that did not affect plasma GH levels, significantly reduced TRL, as well as markers of renal injury, and improved endothelial-dependent vasorelaxation. Glucagon-like peptide 1 (GLP-1) reduces hyperglucagonemia and postprandial TRL, the latter in part through a decreased synthesis of apolipoprotein B-48 (ApoB-48) by intestinal cells. Although plasma GLP-1 levels were elevated in diabetic animals, this was accompanied by increased rather than reduced glucagon levels, suggesting impaired GLP-1 signaling. Treatment with MIA-602 normalized GLP-1 and glucagon to control levels in T1D rats. MIA-602 also decreased secretion of ApoB-48 from rat intestinal epithelial cells in response to oleic acid stimulation in vitro, in part through a GLP-1-dependent mechanism. Our findings support the hypothesis that antagonizing the signaling of GHRH in T1D may improve GLP-1 function in the small intestine, which, in turn, diminishes TRL and reduces renal and vascular complications.

A novel role for the Wnt inhibitor APCDD1 in adipocyte differentiation: Implications for diet-induced obesity.

Impaired adipogenic differentiation during diet-induced obesity (DIO) promotes adipocyte hypertrophy and inflammation, thereby contributing to metabolic disease. Adenomatosis polyposis coli down-regulated 1 (APCDD1) has recently been identified as an inhibitor of Wnt signaling, a key regulator of adipogenic differentiation. Here we report a novel role for APCDD1 in adipogenic differentiation via repression of Wnt signaling and an epigenetic linkage between miR-130 and APCDD1 in DIO. APCDD1 expression was significantly up-regulated in mature adipocytes compared with undifferentiated preadipocytes in both human and mouse subcutaneous adipose tissues. siRNA-based silencing of APCDD1 in 3T3-L1 preadipocytes markedly increased the expression of Wnt signaling proteins (Wnt3a, Wnt5a, Wnt10b, LRP5, and ß-catenin) and inhibited the expression of adipocyte differentiation markers (CCAAT/enhancer-binding protein α (C/EBPα) and peroxisome proliferator-activated receptor γ (PPARγ)) and lipid droplet accumulation, whereas adenovirus-mediated overexpression of APCDD1 enhanced adipogenic differentiation. Notably, DIO mice exhibited reduced APCDD1 expression and increased Wnt expression in both subcutaneous and visceral adipose tissues and impaired adipogenic differentiation in vitro Mechanistically, we found that miR-130, whose expression is up-regulated in adipose tissues of DIO mice, could directly target the 3'-untranslated region of the APCDD1 gene. Furthermore, transfection of an miR-130 inhibitor in preadipocytes enhanced, whereas an miR-130 mimic blunted, adipogenic differentiation, suggesting that miR-130 contributes to impaired adipogenic differentiation during DIO by repressing APCDD1 expression. Finally, human subcutaneous adipose tissues isolated from obese individuals exhibited reduced expression of APCDD1, C/EBPα, and PPARγ compared with those from non-obese subjects. Taken together, these novel findings suggest that APCDD1 positively regulates adipogenic differentiation and that its down-regulation by miR-130 during DIO may contribute to impaired adipogenic differentiation and obesity-related metabolic disease.

MicroRNA-155 Deficiency Leads to Decreased Atherosclerosis, Increased White Adipose Tissue Obesity, and Non-alcoholic Fatty Liver Disease: A NOVEL MOUSE MODEL OF OBESITY PARADOX.

Obesity paradox (OP) describes a widely observed clinical finding of improved cardiovascular fitness and survival in some overweight or obese patients. The molecular mechanisms underlying OP remain enigmatic partly due to a lack of animal models mirroring OP in patients. Using apolipoprotein E knock-out (apoE-/-) mice on a high fat (HF) diet as an atherosclerotic obesity model, we demonstrated 1) microRNA-155 (miRNA-155, miR-155) is significantly up-regulated in the aortas of apoE-/- mice, and miR-155 deficiency in apoE-/- mice inhibits atherosclerosis; 2) apoE-/-/miR-155-/- (double knock-out (DKO)) mice show HF diet-induced obesity, adipocyte hypertrophy, and present with non-alcoholic fatty liver disease; 3) DKO mice demonstrate HF diet-induced elevations of plasma leptin, resistin, fed-state and fasting insulin and increased expression of adipogenic transcription factors but lack glucose intolerance and insulin resistance. Our results are the first to present an OP model using DKO mice with features of decreased atherosclerosis, increased obesity, and non-alcoholic fatty liver disease. Our findings suggest the mechanistic role of reduced miR-155 expression in OP and present a new OP working model based on a single miRNA deficiency in diet-induced obese atherogenic mice. Furthermore, our results serve as a breakthrough in understanding the potential mechanism underlying OP and provide a new biomarker and novel therapeutic target for OP-related metabolic diseases.

Role of Adipose Tissue Endothelial ADAM17 in Age-Related Coronary Microvascular Dysfunction.

OBJECTIVE: A disintegrin and metalloproteinase ADAM17 (tumor necrosis factor-α [TNF]-converting enzyme) regulates soluble TNF levels. We tested the hypothesis that aging-induced activation in adipose tissue (AT)-expressed ADAM17 contributes to the development of remote coronary microvascular dysfunction in obesity. APPROACH AND RESULTS: Coronary arterioles (CAs, ≈90 µm) from right atrial appendages and mediastinal AT were examined in patients (aged: 69±11 years, BMI: 30.2±5.6 kg/m2) who underwent open heart surgery. CA and AT were also studied in 6-month and 24-month lean and obese mice fed a normal or high-fat diet. We found that obesity elicited impaired endothelium-dependent CA dilations only in older patients and in aged high-fat diet mice. Transplantation of AT from aged obese, but not from young or aged, mice increased serum cytokine levels, including TNF, and impaired CA dilation in the young recipient mice. In patients and mice, obesity was accompanied by age-related activation of ADAM17, which was attributed to vascular endothelium-expressed ADAM17. Excess, ADAM17-shed TNF from AT arteries in older obese patients was sufficient to impair CA dilation in a bioassay in which the AT artery was serially connected to a CA. Moreover, we found that the increased activity of endothelial ADAM17 is mediated by a diminished inhibitory interaction with caveolin-1, owing to age-related decline in caveolin-1 expression in obese patients and mice or to genetic deletion of caveolin-1. CONCLUSIONS: The present study indicates that aging and obesity cooperatively reduce caveolin-1 expression and increase vascular endothelial ADAM17 activity and soluble TNF release in AT, which may contribute to the development of remote coronary microvascular dysfunction in older obese patients.

Obesity-induced vascular inflammation involves elevated arginase activity.

Obesity-induced vascular dysfunction involves pathological remodeling of the visceral adipose tissue (VAT) and increased inflammation. Our previous studies showed that arginase 1 (A1) in endothelial cells (ECs) is critically involved in obesity-induced vascular dysfunction. We tested the hypothesis that EC-A1 activity also drives obesity-related VAT remodeling and inflammation. Our studies utilized wild-type and EC-A1 knockout (KO) mice made obese by high-fat/high-sucrose (HFHS) diet. HFHS diet induced increases in body weight, fasting blood glucose, and VAT expansion. This was accompanied by increased arginase activity and A1 expression in vascular ECs and increased expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), interleukin-10 (IL-10), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) mRNA and protein in both VAT and ECs. HFHS also markedly increased circulating inflammatory monocytes and VAT infiltration by inflammatory macrophages, while reducing reparative macrophages. Additionally, adipocyte size and fibrosis increased and capillary density decreased in VAT. These effects of HFHS, except for weight gain and hyperglycemia, were prevented or reduced in mice lacking EC-A1 or treated with the arginase inhibitor 2-(S)-amino-6-boronohexanoic acid (ABH). In mouse aortic ECs, exposure to high glucose (25 mM) and Na palmitate (200 µM) reduced nitric oxide production and increased A1, TNF-α, VCAM-1, ICAM-1, and MCP-1 mRNA, and monocyte adhesion. Knockout of EC-A1 or ABH prevented these effects. HFHS diet-induced VAT inflammation is mediated by EC-A1 expression/activity. Limiting arginase activity is a possible therapeutic means of controlling obesity-induced vascular and VAT inflammation.

Activation of Calpain-2 by Mediators in Pulmonary Vascular Remodeling of Pulmonary Arterial Hypertension.

Calpain mediates collagen synthesis and cell proliferation and plays an important role in pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). In the present study, we investigated whether and how calpain is activated by PAH mediators in pulmonary artery smooth muscle cells (PASMCs). These data show that smooth muscle-specific knockout of calpain attenuated and knockout of calpastatin potentiated pulmonary vascular remodeling and pulmonary hypertension. Treatment of PASMCs with the PAH mediators platelet-derived growth factor (PDGF), serotonin, H2O2, endothelin-1, and IL-6 caused significant increases in calpain activity, cell proliferation, and collagen-I protein level without changes in protein levels of calpain-1 and -2. The calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester) (BAPTA/AM) did not affect calpain activation, but the extracellular signal-regulated kinase (ERK) 1/2 inhibitor PD98059 and knocking down of calpain-2 prevented calpain activation in PAH mediator-treated PASMCs. Mass spectrometry data showed that the phosphorylation of calpain-2 at serine (Ser) 50 was increased and the phosphorylation of calpain-2 at Ser369 was decreased in PDGF-treated PASMCs. The PDGF-induced increase in Ser50 phosphorylation of calpain-2 was prevented by PD98059, whereas dephosphorylation of calpain-2 at Ser369 was blocked by the protein phosphatase 2A inhibitor fostriecin. Furthermore, smooth muscle of pulmonary arteries in PAH animal models and patients with PAH showed higher levels of phospho-Ser50-calpain-2 (P-Ser50) and lower levels of phospho-Ser369-calpain-2 (P-Ser369). These data support that calpain modulates pulmonary vascular remodeling in PAH. PAH mediator-induced activation of calpain is caused by ERK1/2-dependent phosphorylation of calpain-2 at Ser50 and protein phosphatase 2A-dependent dephosphorylation of calpain-2 at Ser369 in pulmonary vascular remodeling of PAH.

Caveolin-1 prevents sustained angiotensin II-induced resistance artery constriction and obesity-induced high blood pressure.

The type 1 angiotensin II (ANG II) receptor (AT1R) undergoes internalization following stimulation by ANG II. Internalization reduces cell surface AT1Rs, and it is required for AT1R resensitization. In this process AT1R may interact with caveolin-1 (Cav1), the main scaffolding protein of caveolae. We hypothesized that the interaction between Cav1 and AT1R delays AT1R resensitization and thereby prevents sustained ANG II-induced resistance artery (RA) constriction under normal conditions and in experimental obesity. In rat and mouse skeletal muscle RA (diameter: ∼90-120 µm) ANG II-induced constrictions were reduced upon repeated (30-min apart) administrations. Upon disruption of caveolae with methyl-ß-cyclodextrin or in RA of Cav1 knockout mice, repeated ANG II applications resulted in essentially maintained constrictions. In vascular smooth muscle cells, AT1R interacted with Cav1, and the degree of cell surface interactions was reduced by long-term (15-min), but not short-term (2-min), exposure to ANG II. When Cav1 was silenced, the amount of membrane-associated AT1R was significantly reduced by a short-term ANG II exposure. Moreover, Cav1 knockout mice fed a high-fat diet exhibited augmented and sustained RA constriction to ANG II and had elevated systemic blood pressure, when compared with normal or high-fat fed wild-type mice. Thus, Cav1, through a direct interaction, delays internalization and subsequent resensitization of AT1R. We suggest that this mechanism prevents sustained ANG II-induced RA constriction and elevated systemic blood pressure in diet-induced obesity.

A novel tumor necrosis factor-mediated mechanism of direct epithelial sodium channel activation.

RATIONALE: Alveolar liquid clearance is regulated by Na(+) uptake through the apically expressed epithelial sodium channel (ENaC) and basolaterally localized Na(+)-K(+)-ATPase in type II alveolar epithelial cells. Dysfunction of these Na(+) transporters during pulmonary inflammation can contribute to pulmonary edema. OBJECTIVES: In this study, we sought to determine the precise mechanism by which the TIP peptide, mimicking the lectin-like domain of tumor necrosis factor (TNF), stimulates Na(+) uptake in a homologous cell system in the presence or absence of the bacterial toxin pneumolysin (PLY). METHODS: We used a combined biochemical, electrophysiological, and molecular biological in vitro approach and assessed the physiological relevance of the lectin-like domain of TNF in alveolar liquid clearance in vivo by generating triple-mutant TNF knock-in mice that express a mutant TNF with deficient Na(+) uptake stimulatory activity. MEASUREMENTS AND MAIN RESULTS: TIP peptide directly activates ENaC, but not the Na(+)-K(+)-ATPase, upon binding to the carboxy-terminal domain of the α subunit of the channel. In the presence of PLY, a mediator of pneumococcal-induced pulmonary edema, this binding stabilizes the ENaC-PIP2-MARCKS complex, which is necessary for the open probability conformation of the channel and preserves ENaC-α protein expression, by means of blunting the protein kinase C-α pathway. Triple-mutant TNF knock-in mice are more prone than wild-type mice to develop edema with low-dose intratracheal PLY, correlating with reduced pulmonary ENaC-α subunit expression. CONCLUSIONS: These results demonstrate a novel TNF-mediated mechanism of direct ENaC activation and indicate a physiological role for the lectin-like domain of TNF in the resolution of alveolar edema during inflammation.

Age-related impairment of conducted dilation in human coronary arterioles.

Conducted vasodilation is essential to coordinate vascular resistance along distances to ensure adequate tissue perfusion. We hypothesized that conducted vasodilation of coronary resistance arteries declines with age. Coronary arterioles were dissected from right atrial appendage of patients (n = 27) undergoing cardiac surgery. Arterioles (~100 µm) were cannulated and pressurized (80 mmHg), and developed spontaneous myogenic tone. Conducted vasodilation was initiated by locally administering the endothelium-dependent agonist bradykinin (BK; 100 µM) ejected from a glass micropipette (~3 µm tip opening, positioned in close proximity to the vessel wall). Diameter changes were measured at local and upstream sites (500 and 1,000 µm from the stimulus) with videomicroscopy. Local administration of BK elicited vasodilation, the magnitude of which increased with the duration of stimulus (69 ± 6, 81 ± 6, 90 ± 2%, after 1, 3, and 5 × 100 ms, respectively). BK-induced dilation remained substantial at upstream sites (500 µm: 53 ± 7%; 1,000 µm: 46 ± 9%). The gap junction uncoupler carbenoxolone or 18-α-glycyrrhetinic acid did not affect local responses, but diminished conducted vasodilation. Inhibitors of small/intermediate conductance calcium-activated potassium channels (SKCa/IKCa), apamin and TRAM34, reduced dilations both at local and remote sites. We found that conducted dilation, but not the local response, was significantly reduced in older (≥64 yr) patients. The nitric oxide (NO) synthesis inhibitor N(ω)-nitro-l-arginine methyl ester did not affect local responses, but markedly reduced conducted dilation in younger (<64 yr) individuals. Collectively, we show that human coronary arterioles exhibit SKCa/IKCa-mediated hyperpolarization spread through gap junctions, which contributes to conducted vasodilation initiated by focal application of BK. We demonstrate that conducted dilation declines with age, likely due to reduced NO availability, which plays a permissive role in propagating longitudinal vasomotor signaling.

Prevention and treatment of no-reflow phenomenon by targeting the coronary microcirculation.

The coronary no-reflow phenomenon refers to the post-percutaneous coronary intervention (PCI) state in which, despite successful revascularization of the epicardial conduit coronary arteries, substantial regions of the myocardium do not receive adequate perfusion. In most cases, the underlying mechanism can be attributed to alterations in the microvascular circulation caused by factors intrinsic or extrinsic to the coronary microcirculation. Because the no-reflow phenomenon is associated with poor clinical outcomes, it is of great importantance to identify and apply effective strategies for reducing post-PCI morbidity and mortality. Successful prevention strategies aim to ad dress increased vasoreactivity, intravascular platelet aggregation, microvascular inflammation, and down-stream plaque particle embolization. This review provides an updated overview on the pathomechanism of no-reflow and the current available prevention strategies from the perspective of coronary microcirculation. Although large randomized clinical trials have not yet identified any effective treatment, studying the coronary microcirculation may reveal new therapeutic targets for successful amelioration of the adverse clinical consequences from no-reflow phenomenon.

Zinc-Dependent Histone Deacetylases in Lung Endothelial Pathobiology.

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and, as such, provides a semi-selective barrier between the blood and the interstitial space. Compromise of the lung EC barrier due to inflammatory or toxic events may result in pulmonary edema, which is a cardinal feature of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS). The EC functions are controlled, at least in part, via epigenetic mechanisms mediated by histone deacetylases (HDACs). Zinc-dependent HDACs represent the largest group of HDACs and are activated by Zn2+. Members of this HDAC group are involved in epigenetic regulation primarily by modifying the structure of chromatin upon removal of acetyl groups from histones. In addition, they can deacetylate many non-histone histone proteins, including those located in extranuclear compartments. Recently, the therapeutic potential of inhibiting zinc-dependent HDACs for EC barrier preservation has gained momentum. However, the role of specific HDAC subtypes in EC barrier regulation remains largely unknown. This review aims to provide an update on the role of zinc-dependent HDACs in endothelial dysfunction and its related diseases. We will broadly focus on biological contributions, signaling pathways and transcriptional roles of HDACs in endothelial pathobiology associated mainly with lung diseases, and we will discuss the potential of their inhibitors for lung injury prevention.

Increased tissue angiotensin-converting enzyme activity impairs bradykinin-induced dilation of coronary arterioles in obesity.

BACKGROUND: Bradykinin (BK) is a key mediator regulating coronary blood flow. It is degraded by angiotensin-converting enzyme (ACE), but what is unknown is whether enhanced tissue ACE activity interferes with BK-induced coronary vasodilation in obesity. METHODS AND RESULTS: Coronary arterioles (~100 µm) were isolated from rats on a normal or high-fat diet (HFD) and from lean or obese patients undergoing heart surgery (n=74). We found that BK-induced dilation was diminished in the coronary arterioles of HFD rats, when compared with controls. When administered in vitro, the ACE inhibitor, captopril, restored the coronary dilation response to BK in HFD rats, but did not affect control responses. Abundant ACE expression was detected in coronary endothelium, which was associated with increased ACE activity in HFD arterioles, as measured by increased response to the ACE substrate, angiotensin I. Moreover, we found that in the coronary arterioles of obese patients, BK-induced dilation was augmented by in vitro captopril administration. Correspondingly, ACE activity was increased in the coronary arterioles of obese patients when compared with the non-obese. Logistic regression analysis revealed that obese patients taking ACE inhibitors prior to surgery exhibited an enhanced dilation response to BK. CONCLUSIONS: We demonstrated augmented tissue ACE activity in the coronary arterioles of obese subjects, which leads to reduced coronary dilation response to BK. We provide a rationale for ACE inhibitor therapy in obese patients to improve dilatation of coronary microvessels.

Mice with endothelial cell-selective adhesion molecule deficiency develop coronary microvascular rarefaction and left ventricle diastolic dysfunction.

Endothelial cell-selective adhesion molecule (ESAM) regulates inflammatory cell adhesion and transmigration and promotes angiogenesis. Here, we examined the role of ESAM in cardiac vascularization, inflammatory cell infiltration, and left ventricle (LV) diastolic function under basal and hemodynamic stress conditions. We employed mice with homozygous genetic deletion of ESAM (ESAM-/- ) and also performed uninephrectomy and aldosterone infusion (UNX-Aldo) to induce volume and pressure overload. Using echocardiography, we found that ESAM-/- mice display no change in systolic function. However, they develop LV diastolic dysfunction, as indicated by a significantly reduced E/A ratio (E = early, A = late mitral inflow peak velocities), increased E/e' ratio, isovolumic relaxation time (IVRT), and E wave deceleration time. An unbiased automated tracing and 3D reconstruction of coronary vasculature revealed that ESAM-/- mice had reduced coronary vascular density. Arteries of ESAM-/- mice exhibited impaired endothelial sprouting and in cultured endothelial cells siRNA-mediated ESAM knockdown reduced tube formation. Changes in ESAM-/- mice were accompanied by elevated myocardial inflammatory cytokine and myeloperoxidase-positive neutrophil levels. Furthermore, UNX-Aldo procedure in wild type mice induced LV diastolic dysfunction, which was accompanied by significantly increased serum ESAM levels. When compared to wild types, ESAM-/- mice with UNX-Aldo displayed worsening of LV diastolic function, as indicated by increased IVRT and pulmonary edema. Thus, we propose that ESAM plays a mechanistic role in proper myocardial vascularization and the maintenance of LV diastolic function under basal and hemodynamic stress conditions.

The role of ADAM17 in cerebrovascular and cognitive function in the APP/PS1 mouse model of Alzheimer's disease.

Introduction: The disintegrin and metalloproteinase 17 (ADAM17) exhibits α-secretase activity, whereby it can prevent the production of neurotoxic amyloid precursor protein-α (APP). ADAM17 is abundantly expressed in vascular endothelial cells and may act to regulate vascular homeostatic responses, including vasomotor function, vascular wall morphology, and formation of new blood vessels. The role of vascular ADAM17 in neurodegenerative diseases remains poorly understood. Here, we hypothesized that cerebrovascular ADAM17 plays a role in the pathogenesis of Alzheimer's disease (AD). Methods and results: We found that 9-10 months old APP/PS1 mice with b-amyloid accumulation and short-term memory and cognitive deficits display a markedly reduced expression of ADAM17 in cerebral microvessels. Systemic delivery and adeno-associated virus (AAV)-mediated re-expression of ADAM17 in APP/PS1 mice improved cognitive functioning, without affecting b-amyloid plaque density. In isolated and pressurized cerebral arteries of APP/PS1 mice the endothelium-dependent dilation to acetylcholine was significantly reduced, whereas the vascular smooth muscle-dependent dilation to the nitric oxide donor, sodium nitroprusside was maintained when compared to WT mice. The impaired endothelium-dependent vasodilation of cerebral arteries in APP/PS1 mice was restored to normal level by ADAM17 re-expression. The cerebral artery biomechanical properties (wall stress and elasticity) and microvascular network density was not affected by ADAM17 re-expression in the APP/PS1 mice. Additionally, proteomic analysis identified several differentially expressed molecules involved in AD neurodegeneration and neuronal repair mechanisms that were reversed by ADAM17 re-expression. Discussion: Thus, we propose that a reduced ADAM17 expression in cerebral microvessels impairs vasodilator function, which may contribute to the development of cognitive dysfunction in APP/PS1 mice, and that ADAM17 can potentially be targeted for therapeutic intervention in AD.