Visceral adipose of obese mice inhibits endothelial inwardly rectifying K+ channels in a CD36-dependent fashion.

Obesity imposes deficits on adipose tissue and vascular endothelium, yet the role that distinct adipose depots play in mediating endothelial dysfunction in local arteries remains unresolved. We recently showed that obesity impairs endothelial Kir2.1 channels, mediators of nitric oxide production, in arteries of visceral adipose tissue (VAT), while Kir2.1 function in subcutaneous adipose tissue (SAT) endothelium remains intact. Therefore, we determined if VAT versus SAT from lean or diet-induced obese mice affected Kir2.1 channel function in vitro. We found that VAT from obese mice reduces Kir2.1 function without altering channel expression whereas AT from lean mice and SAT from obese mice had no effect on Kir2.1 function as compared to untreated control cells. As Kir2.1 is well known to be inhibited by fatty acid derivatives and obesity is strongly associated with elevated circulating fatty acids, we next tested the role of the fatty acid translocase CD36 in mediating VAT-induced Kir2.1 dysfunction. We found that the downregulation of CD36 restored Kir2.1 currents in endothelial cells exposed to VAT from obese mice. In addition, endothelial cells exposed to VAT from obese mice exhibited a significant increase in CD36-mediated fatty acid uptake. The importance of CD36 in obesity-induced endothelial dysfunction of VAT arteries was further supported in ex vivo pressure myography studies where CD36 ablation rescued the endothelium-dependent response to flow via restoring Kir2.1 and endothelial nitric oxide synthase function. These findings provide new insight into the role of VAT in mediating obesity-induced endothelial dysfunction and suggest a novel role for CD36 as a mediator of endothelial Kir2.1 impairment.NEW & NOTEWORTHY Our findings suggest a role for visceral adipose tissue (VAT) in the dysfunction of endothelial Kir2.1 in obesity. We further reveal a role for CD36 as a major contributor to VAT-mediated Kir2.1 and endothelial dysfunction, suggesting that CD36 offers a potential target for preventing the early development of obesity-associated cardiovascular disease.

CD8+ T-cell metabolism is related to cerebrovascular reactivity in middle-aged adults.

Cerebrovascular reactivity (CVR) decreases with advancing age, contributing to increased risk of cognitive impairment; however, the mechanisms underlying the age-related decrease in CVR are incompletely understood. Age-related changes to T cells, such as impaired mitochondrial respiration, increased inflammation, likely contribute to peripheral and cerebrovascular dysfunction in animals. However, whether T-cell mitochondrial respiration is related to cerebrovascular function in humans is not known. Therefore, we hypothesized that peripheral T-cell mitochondrial respiration would be positively associated with CVR and that T-cell glycolytic metabolism would be negatively associated with CVR. Twenty middle-aged adults (58 ± 5 yr) were recruited for this study. T cells were separated from peripheral blood mononuclear cells. Cellular oxygen consumption rate (OCR) and extracellular acidification rate (ECAR, a marker of glycolytic activity) were measured using extracellular flux analysis. CVR was quantified using the breath-hold index (BHI), which reflects the change in blood velocity in the middle-cerebral artery (MCAv) during a 30-s breath-hold. In contrast to our hypothesis, we found that basal OCR in CD8+ T cells (ß = -0.59, R2 = 0.27, P = 0.019) was negatively associated with BHI. However, in accordance with our hypothesis, we found that basal ECAR (ß = -2.20, R2 = 0.29, P = 0.015) and maximum ECAR (ß = -50, R2 = 0.24, P = 0.029) were negatively associated with BHI in CD8+ T cells. There were no associations observed in CD4+ T cells. These associations appeared to be primarily mediated by an association with the pressor response to the breath-hold test. Overall, our findings suggest that CD8+ T-cell respiration and glycolytic activity may influence CVR in humans.NEW & NOTEWORTHY Peripheral T-cell metabolism is related to in vivo cerebrovascular reactivity in humans. Higher glycolytic metabolism in CD8+ T cells was associated with lower cerebrovascular reactivity to a breath-hold in middle-aged adults, which is possibly reflective of a more proinflammatory state in midlife.

Membrane Cholesterol Interactions with Proteins in Hypercholesterolemia-Induced Endothelial Dysfunction.

PURPOSE OF REVIEW: The goal of this review is to highlight work identifying mechanisms driving hypercholesterolemia-mediated endothelial dysfunction. We specifically focus on cholesterol-protein interactions and address specific questions related to the impact of hypercholesterolemia on cellular cholesterol and vascular endothelial function. We describe key approaches used to determine the effects of cholesterol-protein interactions in mediating endothelial dysfunction under dyslipidemic conditions. RECENT FINDINGS: The benefits of removing the cholesterol surplus on endothelial function in models of hypercholesterolemia is clear. However, specific mechanisms driving cholesterol-induced endothelial dysfunction need to be determined. In this review, we detail the latest findings describing cholesterol-mediated endothelial dysfunction, highlighting our studies indicating that cholesterol suppresses endothelial Kir2.1 channels as a major underlying mechanism. The findings detailed in this review support the targeting of cholesterol-induced suppression of proteins in restoring endothelial function in dyslipidemic conditions. The identification of similar mechanisms regarding other cholesterol-endothelial protein interactions is warranted.

Mechanotransduction and the endothelial glycocalyx: Interactions with membrane and cytoskeletal proteins to transduce force.

The endothelial glycocalyx is an extracellular matrix that coats the endothelium and extends into the lumen of blood vessels, acting as a barrier between the vascular wall and blood flowing through the vessel. This positioning of the glycocalyx permits a variety of its constituents, including the major endothelial proteoglycans glypican-1 and syndecan-1, as well as the major glycosaminoglycans heparan sulfate and hyaluronic acid, to contribute to the processes of mechanosensation and subsequent mechanotransduction following such stimuli as elevated shear stress. To coordinate the vast array of processes that occur in response to physical force, the glycocalyx interacts with a plethora of membrane and cytoskeletal proteins to carry out specific signaling pathways resulting in a variety of responses of endothelial cells and, ultimately, blood vessels to mechanical force. This review focuses on proposed glycocalyx-protein relationships whereby the endothelial glycocalyx interacts with a variety of membrane and cytoskeletal proteins to transduce force into a myriad of chemical signaling pathways. The established and proposed interactions at the molecular level are discussed in context of how the glycocalyx regulates membrane/cytoskeletal protein function in the many processes of endothelial mechanotransduction.

Differential effects of obesity on visceral versus subcutaneous adipose arteries: role of shear-activated Kir2.1 and alterations to the glycocalyx.

Obesity imposes well-established deficits to endothelial function. We recently showed that obesity-induced endothelial dysfunction was mediated by disruption of the glycocalyx and a loss of Kir channel flow sensitivity. However, obesity-induced endothelial dysfunction is not observed in all vascular beds: visceral adipose arteries (VAAs), but not subcutaneous adipose arteries (SAAs), exhibit endothelial dysfunction. To determine whether differences in SAA versus VAA endothelial function observed in obesity are attributed to differential impairment of Kir channels and alterations to the glycocalyx, mice were fed a normal rodent diet, or a high-fat Western diet to induce obesity. Flow-induced vasodilation (FIV) was measured ex vivo. Functional downregulation of endothelial Kir2.1 was accomplished by transducing adipose arteries from mice and obese humans with adenovirus containing a dominant-negative Kir2.1 construct. Kir function was tested in freshly isolated endothelial cells seeded in a flow chamber for electrophysiological recordings under fluid shear. Atomic force microscopy was used to assess biophysical properties of the glycocalyx. Endothelial dysfunction was observed in VAAs of obese mice and humans. Downregulating Kir2.1 blunted FIV in SAAs, but had no effect on VAAs, from obese mice and humans. Obesity abolished Kir shear sensitivity in VAA endothelial cells and significantly altered the VAA glycocalyx. In contrast, Kir shear sensitivity was observed in SAA endothelial cells from obese mice and effects on SAA glycocalyx were less pronounced. We reveal distinct differences in Kir function and alterations to the glycocalyx that we propose contribute to the dichotomy in SAA versus VAA endothelial function with obesity.NEW & NOTEWORTHY We identified a role for endothelial Kir2.1 in the differences observed in VAA versus SAA endothelial function with obesity. The endothelial glycocalyx, a regulator of Kir activation by shear, is unequally perturbed in VAAs as compared with SAAs, which we propose results in a near complete loss of VAA endothelial Kir shear sensitivity and endothelial dysfunction. We propose that these differences underly the preserved endothelial function of SAA in obese mice and humans.

New developments in translational microcirculatory research.

Microvascular disease plays a critical role in systemic end-organ dysfunction, and treatment of microvascular pathologies may greatly reduce cardiovascular morbidity and mortality. The Call for Papers collection: New Developments in Translational Microcirculatory Research highlights key advances in our understanding of the role of microvessels in the development of chronic diseases as well as therapeutic strategies to enhance microvascular function. This Mini Review provides a concise summary of these advances and draws from other relevant research to provide the most up-to-date information on the influence of cutaneous, cerebrovascular, coronary, and peripheral microcirculation on the pathophysiology of obesity, hypertension, cardiovascular aging, peripheral artery disease, and cognitive impairment. In addition to these disease- and location-dependent research articles, this Call for Papers includes state-of-the-art reviews on coronary endothelial function and assessment of microvascular health in different organ systems, with an additional focus on establishing rigor and new advances in clinical trial design. These articles, combined with original research evaluating cellular, exosomal, pharmaceutical, exercise, heat, and dietary interventional therapies, establish the groundwork for translating microcirculatory research from bench to bedside. Although numerous studies in this collection are focused on human microcirculation, most used robust preclinical models to probe mechanisms of pathophysiology and interventional benefits. Future work focused on translating these findings to humans are necessary for finding clinical strategies to prevent and treat microvascular dysfunction.

Impairment of Flow-Sensitive Inwardly Rectifying K+ Channels via Disruption of Glycocalyx Mediates Obesity-Induced Endothelial Dysfunction.

OBJECTIVE: To determine if endothelial dysfunction in a mouse model of diet-induced obesity and in obese humans is mediated by the suppression of endothelial Kir (inwardly rectifying K+) channels. Approach and Results: Endothelial dysfunction, observed as reduced dilations to flow, occurred after feeding mice a high-fat, Western diet for 8 weeks. The functional downregulation of endothelial Kir2.1 using dominant-negative Kir2.1 construct resulted in substantial reductions in the response to flow in mesenteric arteries of lean mice, whereas no effect was observed in arteries of obese mice. Overexpressing wild-type-Kir2.1 in endothelium of arteries from obese mice resulted in full recovery of the flow response. Exposing freshly isolated endothelial cells to fluid shear during patch-clamp electrophysiology revealed that the flow-sensitivity of Kir was virtually abolished in cells from obese mice. Atomic force microscopy revealed that the endothelial glycocalyx was stiffer and the thickness of the glycocalyx layer reduced in arteries from obese mice. We also identified that the length of the glycocalyx is critical to the flow-activation of Kir. Overexpressing Kir2.1 in endothelium of arteries from obese mice restored flow- and heparanase-sensitivity, indicating an important role for heparan sulfates in the flow-activation of Kir. Furthermore, the Kir2.1-dependent component of flow-induced vasodilation was lost in the endothelium of resistance arteries of obese humans obtained from biopsies collected during bariatric surgery. CONCLUSIONS: We conclude that obesity-induced impairment of flow-induced vasodilation is attributed to the loss of flow-sensitivity of endothelial Kir channels and propose that the latter is mediated by the biophysical alterations of the glycocalyx.

Cardiovascular mechanosensitive ion channels-Translating physical forces into physiological responses.

Cells and tissues are constantly exposed to mechanical stress. In order to respond to alterations in mechanical stimuli, specific cellular machinery must be in place to rapidly convert physical force into chemical signaling to achieve the desired physiological responses. Mechanosensitive ion channels respond to such physical stimuli in the order of microseconds and are therefore essential components to mechanotransduction. Our understanding of how these ion channels contribute to cellular and physiological responses to mechanical force has vastly expanded in the last few decades due to engineering ingenuities accompanying patch clamp electrophysiology, as well as sophisticated molecular and genetic approaches. Such investigations have unveiled major implications for mechanosensitive ion channels in cardiovascular health and disease. Therefore, in this chapter I focus on our present understanding of how biophysical activation of various mechanosensitive ion channels promotes distinct cell signaling events with tissue-specific physiological responses in the cardiovascular system. Specifically, I discuss the roles of mechanosensitive ion channels in mediating (i) endothelial and smooth muscle cell control of vascular tone, (ii) mechano-electric feedback and cell signaling pathways in cardiomyocytes and cardiac fibroblasts, and (iii) the baroreflex.

LDL induces cholesterol loading and inhibits endothelial proliferation and angiogenesis in Matrigels: correlation with impaired angiogenesis during wound healing.

Hypercholesterolemia is a major risk factor for adverse cardiovascular outcomes, but its effect on angiogenesis and wound healing is not well understood. In this study, using a combination of mass spectrometry and laurdan two-photon imaging, we show that elevated levels of low-density lipoprotein (LDL), like those seen in hypercholesterolemic patients, lead to an increase in both free cholesterol and cholesterol esters, as well as increase in lipid order of endothelial cell membranes. Notably, these effects are distinct and opposite to the lack of cholesterol loading and the disruption of lipid order observed in our earlier studies in response to oxidized LDL (oxLDL). The same pathological level of LDL leads to a significant inhibition of endothelial proliferation and cell cycle arrest in G2/M phase, whereas oxLDL enhances endothelial proliferation in S phase of the cycle. LDL but not oxLDL suppresses the expression of vascular endothelial growth factor receptor-2 while enhancing the expression of vascular endothelial growth factor (VEGF). Furthermore, we show that aged (8-10 mo) hypercholesterolemic apolipoprotein E-deficient (ApoE-/-) mice display delayed wound closure compared with age-matched C57/BL6 wild-type controls following a skin punch biopsy. The delay in wound healing is associated with a decreased expression of cluster of differentiation 31 platelet endothelial cell adhesion molecule endothelial marker and decreased angiogenesis within the wound bed. Furthermore, decreased endothelial responsiveness to the growth factors VEGF and basic fibroblast growth factor is observed in ApoE-/- mice in Matrigel plugs and in Matrigels with high levels of LDL in wild-type mice. We propose that plasma hypercholesterolemia is antiangiogenic due to elevated levels of LDL.

Endothelial inwardly-rectifying K+ channels as a key component of shear stress-induced mechanotransduction.

It has been recognized for decades that fluid shear stress plays a major role in vascular function. Acting on the endothelium shear stress induces vasorelaxation of resistance arteries and plays a major role in the propensity of the major arteries to atherosclerosis. Many elements of shear-induced signaling have been identified yet we are just beginning to decipher the roles that mechanosensitive ion channels may play in the signaling pathways initiated by shear stress. Endothelial inwardly-rectifying K+ channels were identified as potential primary mechanosensors in the late 1980s yet until our recent works, highlighted in the forthcoming chapter, the functional effect of a shear-activated K+ current was completely unknown. In this chapter, we present the physiological effects of shear stress in arteries in health and disease and highlight the most prevalent of today's investigated mechanosensitive ion channels. Ultimately, we focus on Kir2.1 channels and discuss in detail our findings regarding the downstream signaling events that are induced by shear-activated endothelial Kir2.1 channels. Most importantly, we examine our findings regarding hypercholesterolemia-induced inhibition of Kir channel shear-sensitivity and the impact on endothelial function in the context of flow (shear)-mediated vasodilation and atherosclerosis.

Shear-Stress Sensitive Inwardly-Rectifying K+ Channels Regulate Developmental Retinal Angiogenesis by Vessel Regression.

BACKGROUND/AIMS: Shear stress plays major roles in developmental angiogenesis, particularly in blood vessel remodeling and maturation but little is known about the shear stress sensors involved in this process. Our recent study identified endothelial Kir2.1 channels as major contributors to flow-induced vasodilation, a hallmark of the endothelial flow response. The goal of this study is to establish the role of Kir2.1 in the regulation of retinal angiogenesis. METHODS: The retina of newly born Kir2.1+/- mice were used to investigate the sprouting angiogenesis and remodeling of newly formed branched vessels. The structure, blood density and mural cell coverage have been evaluated by immunohistochemistry of the whole-mount retina. Endothelial cell alignment was assessed using CD31 staining. The experiments with flow-induced vasodilation were used to study the cerebrovascular response to flow. RESULTS: Using Kir2.1-deficient mice, we show that the retinas of Kir2.1+/- mice have higher vessel density, increased lengths and increased number of the branching points, as compared to WT littermates. In contrast, the coverage by αSMA is decreased in Kir2.1+/- mice while pericyte coverage does not change. Furthermore, to determine whether deficiency of Kir2.1 affects vessel pruning, we discriminated between intact and degraded vessels or "empty matrix sleeves" and found a significant reduction in the number of empty sleeves on the peripheral part of the retina or "angiogenic front" in Kir2.1+/- mice. We also show that Kir2.1 deficiency results in decreased endothelial alignment in retinal endothelium and impaired flow-induced vasodilation of cerebral arteries, verifying the involvement of Kir2.1 in shear-stress sensing in retina and cerebral circulation. CONCLUSION: This study shows that shear-stress sensitive Kir2.1 channels play an important role in pruning of excess vessels and vascular remodeling during retinal angiogenesis. We propose that Kir2.1 mediates the effect of shear stress on vessel maturation.

Proatherogenic Flow Increases Endothelial Stiffness via Enhanced CD36-Mediated Uptake of Oxidized Low-Density Lipoproteins.

OBJECTIVE: Disturbed flow (DF) is well-known to induce endothelial dysfunction and synergistically with plasma dyslipidemia facilitate plaque formation. Little is known, however, about the synergistic impact of DF and dyslipidemia on endothelial biomechanics. Our goal was to determine the impact of DF on endothelial stiffness and evaluate the role of dyslipidemia/oxLDL (oxidized low-density lipoprotein) in this process. APPROACH AND RESULTS: Endothelial elastic modulus of intact mouse aortas ex vivo and of human aortic endothelial cells exposed to laminar flow or DF was measured using atomic force microscopy. Endothelial monolayer of the aortic arch is found to be significantly stiffer than the descending aorta (4.2+1.1 versus 2.5+0.2 kPa for aortic arch versus descending aorta) in mice maintained on low-fat diet. This effect is significantly exacerbated by short-term high-fat diet (8.7+2.5 versus 4.5+1.2 kPa for aortic arch versus descending aorta). Exposure of human aortic endothelial cells to DF in vitro resulted in 50% increase in oxLDL uptake and significant endothelial stiffening in the presence but not in the absence of oxLDL. DF also increased the expression of oxLDL receptor CD36 (cluster of differentiation 36), whereas downregulation of CD36 abrogated DF-induced endothelial oxLDL uptake and stiffening. Furthermore, genetic deficiency of CD36 abrogated endothelial stiffening in the aortic arch in vivo in mice fed either low-fat diet or high-fat diet. We also show that the loss of endothelial stiffening in CD36 knockout aortas is not mediated by the loss of CD36 in circulating cells. CONCLUSIONS: DF facilitates endothelial CD36-dependent uptake of oxidized lipids resulting in local increase of endothelial stiffness in proatherogenic areas of the aorta.

Microvascular Vasodilator Plasticity After Acute Exercise.

Endothelium-dependent vasodilation is reduced after acute exercise or after high intraluminal pressure in isolated arterioles from sedentary adults but not in arterioles from regular exercisers. The preserved vasodilation in arterioles from exercisers is hydrogen peroxide (H2O2) dependent, whereas resting dilation is nitric oxide (NO) dependent. We hypothesize chronic exercise elicits adaptations allowing for maintained vasodilation when NO bioavailability is reduced.

Inwardly rectifying K+ channels are major contributors to flow-induced vasodilatation in resistance arteries.

KEY POINTS: Endothelial inwardly rectifying K+ (Kir2.1) channels regulate flow-induced vasodilatation via nitric oxide (NO) in mouse mesenteric resistance arteries. Deficiency of Kir2.1 channels results in elevated blood pressure and increased vascular resistance. Flow-induced vasodilatation in human resistance arteries is also regulated by inwardly rectifying K+ channels. This study presents the first direct evidence that Kir channels play a critical role in physiological endothelial responses to flow. ABSTRACT: Inwardly rectifying K+ (Kir) channels are known to be sensitive to flow, but their role in flow-induced endothelial responses is not known. The goal of this study is to establish the role of Kir channels in flow-induced vasodilatation and to provide first insights into the mechanisms responsible for Kir signalling in this process. First, we establish that primary endothelial cells isolated from murine mesenteric arteries express functional Kir2.1 channels sensitive to shear stress. Then, using the Kir2.1+/- heterozygous mouse model, we establish that downregulation of Kir2.1 results in significant decrease in shear-activated Kir currents and inhibition of endothelium-dependent flow-induced vasodilatation (FIV) assayed in pressurized mesenteric arteries pre-constricted with endothelin-1. Deficiency in Kir2.1 also results in the loss of flow-induced phosphorylation of eNOS and Akt, as well as inhibition of NO generation. All the effects are fully rescued by endothelial cell (EC)-specific overexpression of Kir2.1. A component of FIV that is Kir independent is abrogated by blocking Ca2+ -sensitive K+ channels. Kir2.1 has no effect on endothelium-independent and K+ -induced vasodilatation in denuded arteries. Kir2.1+/- mice also show increased mean blood pressure measured by carotid artery cannulation and increased microvascular resistance measured using a tail-cuff. Importantly, blocking Kir channels also inhibits flow-induced vasodilatation in human subcutaneous adipose microvessels. Endothelial Kir channels contribute to FIV of mouse mesenteric arteries via an NO-dependent mechanism, whereas Ca2+ -sensitive K+ channels mediate FIV via an NO-independent pathway. Kir2 channels also regulate vascular resistance and blood pressure. Finally, Kir channels also contribute to FIV in human subcutaneous microvessels.

Short-term regular aerobic exercise reduces oxidative stress produced by acute in the adipose microvasculature.

High blood pressure has been shown to elicit impaired dilation in the vasculature. The purpose of this investigation was to elucidate the mechanisms through which high pressure may elicit vascular dysfunction and determine the mechanisms through which regular aerobic exercise protects arteries against high pressure. Male C57BL/6J mice were subjected to 2 wk of voluntary running (~6 km/day) for comparison with sedentary controls. Hindlimb adipose resistance arteries were dissected from mice for measurements of flow-induced dilation (FID; with or without high intraluminal pressure exposure) or protein expression of NADPH oxidase II (NOX II) and superoxide dismutase (SOD). Microvascular endothelial cells were subjected to high physiological laminar shear stress (20 dyn/cm2) or static condition and treated with ANG II + pharmacological inhibitors. Cells were analyzed for the detection of ROS or collected for Western blot determination of NOX II and SOD. Resistance arteries from exercised mice demonstrated preserved FID after high pressure exposure, whereas FID was impaired in control mouse arteries. Inhibition of ANG II or NOX II restored impaired FID in control mouse arteries. High pressure increased superoxide levels in control mouse arteries but not in exercise mouse arteries, which exhibited greater ability to convert superoxide to H2O2 Arteries from exercised mice exhibited less NOX II protein expression, more SOD isoform expression, and less sensitivity to ANG II. Endothelial cells subjected to laminar shear stress exhibited less NOX II subunit expression. In conclusion, aerobic exercise prevents high pressure-induced vascular dysfunction through an improved redox environment in the adipose microvasculature.NEW & NOTEWORTHY We describe potential mechanisms contributing to aerobic exercise-conferred protection against high intravascular pressure. Subcutaneous adipose microvessels from exercise mice express less NADPH oxidase (NOX) II and more superoxide dismutase (SOD) and demonstrate less sensitivity to ANG II. In microvascular endothelial cells, shear stress reduced NOX II but did not influence SOD expression.

Roles of NADPH oxidase and mitochondria in flow-induced vasodilation of human adipose arterioles: ROS-induced ROS release in coronary artery disease.

OBJECTIVES: H2 O2 contributes to FID of human arterioles. This study is designed to examine the roles of mitochondria and NADPH oxidase in modulating the release of ROS and in mediating FID. We tested whether NADPH oxidase contributes to mitochondrial ROS generation in arterioles during CAD. METHODS: Visceral adipose arterioles obtained from patients with or without CAD were cannulated and pressurized for videomicroscopic measurement of arteriolar diameters. Dilator responses and ROS production during flow were determined in the presence and absence of the NADPH oxidase inhibitor gp91ds-tat and the mitochondrial electron transport inhibitor rotenone. RESULTS: Both dilation and H2 O2 generation during flow were reduced in the presence of rotenone (13.5±8% vs 97±% without rotenone) or gp91ds-tat in patients with CAD, while patients without CAD exhibited H2 O2 -independent dilations. Mitochondrial superoxide production during flow was attenuated by gp91ds-tat in arterioles from CAD patients. CONCLUSIONS: These findings indicate that ROS produced by NADPH oxidase are an upstream component of the mitochondria-dependent pathway contributing to flow-dependent H2 O2 generation and dilation in peripheral microvessels from patients with CAD. We conclude that in CAD, both mitochondria and NADPH oxidase contribute to FID through a redox mechanism in visceral arterioles.

Nonpharmacologic management of hypertension: a multidisciplinary approach.

PURPOSE OF REVIEW: Nonpharmacologic lifestyle modification interventions (LMIs), such as increasing physical activity, dietary modification, weight-loss, reducing alcohol consumption and smoking cessation, are effective strategies to lower resting blood pressures (BPs) in prehypertensive or hypertensive patients. However, the limited time shared between a physician and a patient is not adequate to instill an adoption of LMI. The purpose of this review is to therefore highlight evidence-based BP lowering, LMI strategies that can feasibly be implemented in clinical practices. RECENT FINDINGS: Interventions focusing on modifying physical activity, diet, weight-loss, drinking and smoking habits have established greater efficacy in reducing elevated BP compared with providing guideline recommendations based on national guidelines. Alone greater reductions in BP can be achieved through programmes that provide frequent contact time with exercise, nutrition and/or wellness professionals. Programmes that educate individuals to lead peer support groups can be an efficient method of ensuring compliance to LMI. SUMMARY: Evidence of a multidisciplinary approach to LMI is an effective and attractive model in managing elevated BP. This strategy is an attractive model that provides the necessary patient attention to confer lifestyle maintenance.

Differential regulation of TRPV1 channels by H2O2: implications for diabetic microvascular dysfunction.

We demonstrated previously that TRPV1-dependent coupling of coronary blood flow (CBF) to metabolism is disrupted in diabetes. A critical amount of H2O2 contributes to CBF regulation; however, excessive H2O2 impairs responses. We sought to determine the extent to which differential regulation of TRPV1 by H2O2 modulates CBF and vascular reactivity in diabetes. We used contrast echocardiography to study TRPV1 knockout (V1KO), db/db diabetic, and wild type C57BKS/J (WT) mice. H2O2 dose-dependently increased CBF in WT mice, a response blocked by the TRPV1 antagonist SB366791. H2O2-induced vasodilation was significantly inhibited in db/db and V1KO mice. H2O2 caused robust SB366791-sensitive dilation in WT coronary microvessels; however, this response was attenuated in vessels from db/db and V1KO mice, suggesting H2O2-induced vasodilation occurs, in part, via TRPV1. Acute H2O2 exposure potentiated capsaicin-induced CBF responses and capsaicin-mediated vasodilation in WT mice, whereas prolonged luminal H2O2 exposure blunted capsaicin-induced vasodilation. Electrophysiology studies re-confirms acute H2O2 exposure activated TRPV1 in HEK293A and bovine aortic endothelial cells while establishing that H2O2 potentiate capsaicin-activated TRPV1 currents, whereas prolonged H2O2 exposure attenuated TRPV1 currents. Verification of H2O2-mediated activation of intrinsic TRPV1 specific currents were found in isolated mouse coronary endothelial cells from WT mice and decreased in endothelial cells from V1KO mice. These data suggest prolonged H2O2 exposure impairs TRPV1-dependent coronary vascular signaling. This may contribute to microvascular dysfunction and tissue perfusion deficits characteristic of diabetes.

Diphenyl phosphine oxide-1-sensitive K(+) channels contribute to the vascular tone and reactivity of resistance arteries from brain and skeletal muscle.

OBJECTIVE: Many types of vascular smooth muscle cells exhibit prominent KDR currents. These KDR currents may be mediated, at least in part, by KV1.5 channels, which are sensitive to inhibition by DPO-1. We tested the hypothesis that DPO-1-sensitive KDR channels regulate the tone and reactivity of resistance-sized vessels from rat brain (MCA) and skeletal muscle (GA). METHODS: Middle cerebral and gracilis arteries were isolated and subjected to three kinds of experimental analysis: (i) western blot/immunocytochemistry; (ii) patch clamp electrophysiology; and (iii) pressure myography. RESULTS: Western blot and immunocytochemistry experiments demonstrated KV1.5 immunoreactivity in arteries and smooth muscle cells isolated from them. Whole-cell patch clamp experiments revealed smooth muscle cells from resistance-sized arteries to possess a KDR current that was blocked by DPO-1. Resistance arteries constricted in response to increasing concentrations of DPO-1. DPO-1 enhanced constrictions to PE and serotonin in gracilis and middle cerebral arteries, respectively. When examining the myogenic response, we found that DPO-1 reduced the diameter at any given pressure. Dilations in response to ACh and SNP were reduced by DPO-1. CONCLUSION: We suggest that KV1.5, a DPO-1-sensitive KDR channel, plays a major role in determining microvascular tone and the response to vasoconstrictors and vasodilators.