Publications by authors named "Michael A Hill"

99 Publications

Obesity, Adipose Tissue and Vascular Dysfunction.

Circ Res 2021 Apr 1;128(7):951-968. Epub 2021 Apr 1.

Dalton Cardiovascular Research Center, University of Missouri, Columbia (M.A.H., J.R.S.).

Cardiovascular diseases are the leading cause of death worldwide. Overweight and obesity are strongly associated with comorbidities such as hypertension and insulin resistance, which collectively contribute to the development of cardiovascular diseases and resultant morbidity and mortality. Forty-two percent of adults in the United States are obese, and a total of 1.9 billion adults worldwide are overweight or obese. These alarming numbers, which continue to climb, represent a major health and economic burden. Adipose tissue is a highly dynamic organ that can be classified based on the cellular composition of different depots and their distinct anatomical localization. Massive expansion and remodeling of adipose tissue during obesity differentially affects specific adipose tissue depots and significantly contributes to vascular dysfunction and cardiovascular diseases. Visceral adipose tissue accumulation results in increased immune cell infiltration and secretion of vasoconstrictor mediators, whereas expansion of subcutaneous adipose tissue is less harmful. Therefore, fat distribution more than overall body weight is a key determinant of the risk for cardiovascular diseases. Thermogenic brown and beige adipose tissue, in contrast to white adipose tissue, is associated with beneficial effects on the vasculature. The relationship between the type of adipose tissue and its influence on vascular function becomes particularly evident in the context of the heterogenous phenotype of perivascular adipose tissue that is strongly location dependent. In this review, we address the abnormal remodeling of specific adipose tissue depots during obesity and how this critically contributes to the development of hypertension, endothelial dysfunction, and vascular stiffness. We also discuss the local and systemic roles of adipose tissue derived secreted factors and increased systemic inflammation during obesity and highlight their detrimental impact on cardiovascular health.
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http://dx.doi.org/10.1161/CIRCRESAHA.121.318093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8026272PMC
April 2021

Insulin resistance, cardiovascular stiffening and cardiovascular disease.

Metabolism 2021 Mar 22:154766. Epub 2021 Mar 22.

Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, 65211, USA; Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO, 65212, USA; Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA; Department of Medicine, University of Missouri School of Medicine, Columbia, MO, 65212, USA. Electronic address:

The cardiometabolic syndrome (CMS) and obesity are typically characterized by a state of metabolic insulin resistance. As global and US rates of obesity increase there is an acceleration of the incidence and prevalence of insulin resistance along with associated cardiovascular disease (CVD). Under physiological conditions insulin regulates glucose homeostasis by enhancing glucose disposal in insulin sensitive tissues while also regulating delivery of nutrients through its vasodilation actions on small feed arteries. Specifically, insulin-mediated production of nitric oxide from the vascular endothelium leads to increased blood flow enhancing disposal of glucose. Typically, insulin resistance is considered as a decrease in sensitivity or responsiveness to the metabolic actions of insulin including insulin-mediated glucose disposal. However, a decreased sensitivity to the normal vascular actions of insulin, especially diminished nitric oxide production, plays an additional important role in the development of CVD in states of insulin resistance. One mechanism by which insulin resistance and attendant hyperinsulinemia promote CVD is via increases in vascular stiffness. Although obesity and insulin resistance are known to be associated with substantial increases in the prevalence of vascular fibrosis and stiffness the mechanisms and mediators that underlie vascular stiffening in insulin resistant states are complex and have only recently begun to be addressed. Current evidence supports the role of increased plasma levels of aldosterone and insulin and attendant reductions in bioavailable nitric oxide in the pathogenesis of impaired vascular relaxation and vascular stiffness in the CMS and obesity. Aldosterone and insulin both increase the activity of serum and glucocorticoid kinase 1 (SGK-1) which in turn is a major regulator of vascular and renal sodium (Na channel activity.The importance of SGK-1 in the pathogenesis of the CMS is highlighted by observations that gain of function mutations in SGK-1 in humans promotes hypertension, insulin resistance and obesity. In endothelial cells, an increase in Na flux contributes to remodeling of the cytoskeleton, reduced NO bioavailability and vascular stiffening. Thus, endothelial SGK-1 may represent a point of convergence for insulin and aldosterone signaling in arterial stiffness associated with obesity and the CMS. This review examines our contemporary understanding of the link between insulin resistance and increased vascular stiffness with emphasis placed on a role for enhanced SGK-1 signaling as a key node in this pathological process.
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http://dx.doi.org/10.1016/j.metabol.2021.154766DOI Listing
March 2021

Role of the vascular endothelial sodium channel activation in the genesis of pathologically increased cardiovascular stiffness.

Cardiovasc Res 2020 Nov 3. Epub 2020 Nov 3.

Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA.

Cardiovascular (CV) stiffening represents a complex series of events evolving from pathological changes in individual cells of the vasculature and heart which leads to overt tissue fibrosis. While vascular stiffening occurs naturally with ageing it is accelerated in states of insulin (INS) resistance, such as obesity and type 2 diabetes. CV stiffening is clinically manifested as increased arterial pulse wave velocity and myocardial fibrosis-induced diastolic dysfunction. A key question that remains is how are these events mechanistically linked. In this regard, heightened activation of vascular mineralocorticoid receptors (MR) and hyperinsulinaemia occur in obesity and INS resistance states. Further, a downstream mediator of MR and INS receptor activation, the endothelial cell Na+ channel (EnNaC), has recently been identified as a key molecular determinant of endothelial dysfunction and CV fibrosis and stiffening. Increased activity of the EnNaC results in a number of negative consequences including stiffening of the cortical actin cytoskeleton in endothelial cells, impaired endothelial NO release, increased oxidative stress-meditated NO destruction, increased vascular permeability, and stimulation of an inflammatory environment. Such endothelial alterations impact vascular function and stiffening through regulation of vascular tone and stimulation of tissue remodelling including fibrosis. In the case of the heart, obesity and INS resistance are associated with coronary vascular endothelial stiffening and associated reductions in bioavailable NO leading to heart failure with preserved systolic function (HFpEF). After a brief discussion on mechanisms leading to vascular stiffness per se, this review then focuses on recent findings regarding the role of INS and aldosterone to enhance EnNaC activity and associated CV stiffness in obesity/INS resistance states. Finally, we discuss how coronary artery-mediated EnNaC activation may lead to cardiac fibrosis and HFpEF, a condition that is especially pronounced in obese and diabetic females.
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http://dx.doi.org/10.1093/cvr/cvaa326DOI Listing
November 2020

Commentary: COVID-19 and obesity pandemics converge into a syndemic requiring urgent and multidisciplinary action.

Metabolism 2021 01 17;114:154408. Epub 2020 Oct 17.

Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, The Section of Endocrinology, VA Boston Healthcare System and Harvard Medical School, Boston, MA, United States of America.

While substantial evidence points towards obesity and associated cardiometabolic disorders being a major factor for poor outcomes in SARS-CoV2 infections (COVID-19), the complexity of the interplay between these two pandemics is becoming apparent. Indeed, as previously defined, this interaction between obesity and COVID-19 represents a 'syndemic' that requires both current and ongoing attention. At a mechanistic level the chronic inflammatory environment of obesity predisposes to life threatening events such as cytokine storm and enhanced coagulopathy. Obesity and its management are affected by diverse factors manifested at societal, educational, racial, and nutritional levels. A multidisciplinary approach is required to manage obese and type 2 diabetic patients, not only during the current COVID-19 crisis, but to decrease the growing burden of cardiometabolic disease and associated cardiovascular complications impacting future viral pandemics. Further, this syndemic has highlighted disparities in healthcare which need to be addressed to achieve equality in health outcomes in patients infected with COVID-19.
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http://dx.doi.org/10.1016/j.metabol.2020.154408DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7831812PMC
January 2021

Frontiers in Vascular Physiology Grand Challenges in Vascular Physiology.

Front Physiol 2020 7;11:852. Epub 2020 Aug 7.

Dalton Cardiovascular Research Center and Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States.

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http://dx.doi.org/10.3389/fphys.2020.00852DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7426502PMC
August 2020

Regulation of blood flow in small arteries: mechanosensory events underlying myogenic vasoconstriction.

J Exerc Rehabil 2020 Jun 30;16(3):207-215. Epub 2020 Jun 30.

Dalton Cardiovascular Research Center, University of Missouri-School of Medicine, Columbia, MO, USA.

As blood flow is proportional to the fourth power of the vascular radius small changes in the diameter of resistance arteries/arterioles following an increase in intraluminal pressure would be expected to substantially increase blood flow. However, arteriolar myocytes display an intrinsic ability to locally regulate blood flow according to metabolic demands by tuning the diameter of small arteries in response to local changes in he-modynamics. Critical to this, observations were made more than 100 years ago that mechanosensitive small arteries exhibit the "myogenic response" or pressure-induced vasoconstriction or vasodilation in re-sponse to increased or decreased intravascular pressure, respectively. Although cellular mechanisms underlying the myogenic response have now been studied extensively, the precise cellular mechanisms under-lying this intriguing phenomenon still remain uncertain. In particular, the biological machinery that senses changes in intravascular pressure in vascular smooth muscle cells have not been unquestionably identified and remain a significant issue in vascular biology to be fully elucidated. As such, this brief review focuses on putative mechanosensors that have been proposed to contribute to myogenic vasoreactivity. Specific attention is paid to the roles of integrins, G protein-coupled receptors, and cadherins.
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http://dx.doi.org/10.12965/jer.2040432.216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7365734PMC
June 2020

Covid-19 and Disparities in Nutrition and Obesity.

N Engl J Med 2020 Sep 15;383(11):e69. Epub 2020 Jul 15.

From the Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School (M.J.B., A.M.A., C.S.M.), and the Section of Endocrinology, VA Boston Healthcare System and Harvard Medical School (C.S.M.) - both in Boston; the Dalton Cardiovascular Research Center and the Department of Medical Pharmacology and Physiology (M.A.H., J.R.S.) and the Diabetes and Cardiovascular Research Center (J.R.S.), University of Missouri, Columbia; and the Department of Biologic Chemistry, School of Medicine, National and Kapodistrian University of Athens, Athens (M.D.).

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http://dx.doi.org/10.1056/NEJMp2021264DOI Listing
September 2020

Discovery of novel L-type voltage-gated calcium channel blockers and application for the prevention of inflammation and angiogenesis.

J Neuroinflammation 2020 Apr 25;17(1):132. Epub 2020 Apr 25.

Department of Ophthalmology, School of Medicine, University of Missouri-Columbia, 1 Hospital Drive, MA102C, Columbia, MO, 65212, USA.

Background: The ways in which microglia activate and promote neovascularization (NV) are not fully understood. Recent in vivo evidence supports the theory that calcium is required for the transition of microglia from a surveillance state to an active one. The objectives of this study were to discover novel L-type voltage-gated channel (L-VGCC) blockers and investigate their application for the prevention of inflammation and angiogenesis.

Methods: Pharmacophore-based computational modeling methods were used to screen for novel calcium channel blockers (CCBs) from the ZINC compound library. The effects of CCBs on calcium blockade, microglial pro-inflammatory activation, and cell toxicity were validated in BV-2 microglial cell and freshly isolated smooth muscle cell (SMC) cultures. Laser-induced choroidal neovascularization (NV) and the suture-induced inflammatory corneal NV models of angiogenesis were used for in vivo validation of the novel CCBs. CX3CR1 mice were used to examine the infiltration of GFP-labeled microglial cells.

Results: We identified three compounds from the ZINC database (Zinc20267861, Zinc18204217, and Zinc33254827) as new blockers of L-type voltage-gated calcium channels (L-VGCC) using a structure-based pharmacophore approach. The effects of the three CCBs on Ca influx into cells were verified in BV-2 microglial cells using Fura-2 fluorescent dye and in freshly isolated SMCs using the voltage-patch clamp. All three CCBs reduced microglial cell migration, activation stimulated by lipopolysaccharide (LPS), and reduced the expression of the inflammatory markers NF-κB (phospho-IκBα) and cyclooxygenase-2 (COX-2) as well as reactive oxygen species. Of the three compounds, we further examined the in vivo activity of Zinc20267861. Topical treatment with Zinc20267861 in a rat model of suture-induced inflammatory cornea neovascularization demonstrated efficacy of the compound in reducing monocyte infiltration and overall corneal NV response. Subconjunctival administration of the compound in the choroidal NV mouse model effectively prevented CNV and microglial infiltration.

Conclusions: Our findings suggest that the novel CCBs identified here are effective anti-inflammatory agents that can be further evaluated for treating NV disorders and can be potentially applied in the treatment of ocular inflammatory and pathological angiogenetic disorders.
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http://dx.doi.org/10.1186/s12974-020-01801-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7183139PMC
April 2020

Western diet induces renal artery endothelial stiffening that is dependent on the epithelial Na channel.

Am J Physiol Renal Physiol 2020 05 13;318(5):F1220-F1228. Epub 2020 Apr 13.

Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri.

Consumption of a Western diet (WD) induces central aortic stiffening that contributes to the transmittance of pulsatile blood flow to end organs, including the kidney. Our recent work supports that endothelial epithelial Na channel (EnNaC) expression and activation enhances aortic endothelial cell stiffening through reductions in endothelial nitric oxide (NO) synthase (eNOS) and bioavailable NO that result in inflammatory and oxidant responses and perivascular fibrosis. However, the role that EnNaC activation has on endothelial responses in the renal circulation remains unknown. We hypothesized that cell-specific deletion of the α-subunit of EnNaC would prevent WD-induced central aortic stiffness and protect the kidney from endothelial dysfunction and vascular stiffening. Twenty-eight-week-old female αEnNaC knockout and wild-type mice were fed either mouse chow or WD containing excess fat (46%), sucrose, and fructose (17.5% each). WD feeding increased fat mass, indexes of vascular stiffening in the aorta and renal artery (in vivo pulse wave velocity and ultrasound), and renal endothelial cell stiffening (ex vivo atomic force microscopy). WD further impaired aortic endothelium-dependent relaxation and renal artery compliance (pressure myography) without changes in blood pressure. WD-induced renal arterial stiffening occurred in parallel to attenuated eNOS activation, increased oxidative stress, and aortic and renal perivascular fibrosis. αEnNaC deletion prevented these abnormalities and support a novel mechanism by which WD contributes to renal arterial stiffening that is endothelium and Na channel dependent. These results demonstrate that cell-specific EnNaC is important in propagating pulsatility into the renal circulation, generating oxidant stress, reduced bioavailable NO, and renal vessel wall fibrosis and stiffening.
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http://dx.doi.org/10.1152/ajprenal.00517.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7395479PMC
May 2020

Endothelial sodium channel activation promotes cardiac stiffness and diastolic dysfunction in Western diet fed female mice.

Metabolism 2020 08 7;109:154223. Epub 2020 Apr 7.

Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA; Department of Medicine, University of Missouri School of Medicine, Columbia, MO 65212, USA. Electronic address:

Objective: Obesity is associated with myocardial fibrosis and impaired diastolic relaxation, abnormalities that are especially prevalent in women. Normal coronary vascular endothelial function is integral in mediating diastolic relaxation, and recent work suggests increased activation of the endothelial cell (EC) mineralocorticoid receptor (ECMR) is associated with impaired diastolic relaxation. As the endothelial Na channel (EnNaC) is a downstream target of the ECMR, we sought to determine whether EC-specific deletion of the critical alpha subunit, αEnNaC, would prevent diet induced-impairment of diastolic relaxation in female mice.

Methods And Materials: Female αEnNaC KO mice and littermate controls were fed a Western diet (WD) high in fat (46%), fructose corn syrup (17.5%) and sucrose (17.5%) for 12-16 weeks. Measurements were conducted for in vivo cardiac function, in vitro cardiomyocyte stiffness and EnNaC activity in primary cultured ECs. Additional biochemical studies examined indicators of oxidative stress, including aspects of antioxidant Nrf2 signaling, in cardiac tissue.

Results: Deletion of αEnNaC in female mice fed a WD significantly attenuated WD mediated impairment in diastolic relaxation. Improved cardiac relaxation was accompanied by decreased EnNaC-mediated Na currents in ECs and reduced myocardial oxidative stress. Further, deletion of αEnNaC prevented WD-mediated increases in isolated cardiomyocyte stiffness.

Conclusion: Collectively, these findings support the notion that WD feeding in female mice promotes activation of EnNaC in the vasculature leading to increased cardiomyocyte stiffness and diastolic dysfunction.
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http://dx.doi.org/10.1016/j.metabol.2020.154223DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7676474PMC
August 2020

Commentary: COVID-19 in patients with diabetes.

Metabolism 2020 06 24;107:154217. Epub 2020 Mar 24.

Dalton Cardiovascular Research Center, Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA; Diabetes and Cardiovascular Center, University of Missouri-Columbia School of Medicine, Columbia, MO, USA. Electronic address:

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http://dx.doi.org/10.1016/j.metabol.2020.154217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7102643PMC
June 2020

Measurement of Pulse Propagation Velocity, Distensibility and Strain in an Abdominal Aortic Aneurysm Mouse Model.

J Vis Exp 2020 02 23(156). Epub 2020 Feb 23.

Division of Cardiovascular Medicine, University of Missouri; Medical Pharmacology and Physiology, University of Missouri; Dalton Cardiovascular Research Center, University of Missouri;

An abdominal aortic aneurysm (AAA) is defined as a localized dilation of the abdominal aorta that exceeds the maximal intraluminal diameter (MILD) by 1.5 times of its original size. Clinical and experimental studies have shown that small aneurysms may rupture, while a subpopulation of large aneurysms may remain stable. Thus, in addition to the measurement of intraluminal diameter of the aorta, knowledge of structural traits of the vessel wall may provide important information to assess the stability of the AAA. Aortic stiffening has recently emerged as a reliable tool to determine early changes in the vascular wall. Pulse propagation velocity (PPV) along with the distensibility and radial strain are highly useful ultrasound-based methods relevant for assessing aortic stiffness. The primary purpose of this protocol is to provide a comprehensive technique for the use of ultrasound imaging system to acquire images and analyze the structural and functional properties of the aorta as determined by MILD, PPV, distensibility and radial strain.
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http://dx.doi.org/10.3791/60515DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7890464PMC
February 2020

Sexual Dimorphism in Obesity-Associated Endothelial ENaC Activity and Stiffening in Mice.

Endocrinology 2019 12;160(12):2918-2928

Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri.

Obesity and insulin resistance stiffen the vasculature, with females appearing to be more adversely affected. As augmented arterial stiffness is an independent predictor of cardiovascular disease (CVD), the increased predisposition of women with obesity and insulin resistance to arterial stiffening may explain their heightened risk for CVD. However, the cellular mechanisms by which females are more vulnerable to arterial stiffening associated with obesity and insulin resistance remain largely unknown. In this study, we provide evidence that female mice are more susceptible to Western diet-induced endothelial cell stiffening compared with age-matched males. Mechanistically, we show that the increased stiffening of the vascular intima in Western diet-fed female mice is accompanied by enhanced epithelial sodium channel (ENaC) activity in endothelial cells (EnNaC). Our data further indicate that: (i) estrogen signaling through estrogen receptor α (ERα) increases EnNaC activity to a larger extent in females compared with males, (ii) estrogen-induced activation of EnNaC is mediated by the serum/glucocorticoid inducible kinase 1 (SGK-1), and (iii) estrogen signaling stiffens endothelial cells when nitric oxide is lacking and this stiffening effect can be reduced with amiloride, an ENaC inhibitor. In aggregate, we demonstrate a sexual dimorphism in obesity-associated endothelial stiffening, whereby females are more vulnerable than males. In females, endothelial stiffening with obesity may be attributed to estrogen signaling through the ERα-SGK-1-EnNaC axis, thus establishing a putative therapeutic target for female obesity-related vascular stiffening.
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http://dx.doi.org/10.1210/en.2019-00483DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6853665PMC
December 2019

Maternal Exposure to High Fructose and Offspring Health.

Hypertension 2019 09 22;74(3):499-501. Epub 2019 Jul 22.

From the Diabetes and Cardiovascular Research Center (G.J., J.R.S.), Columbia, MO.

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http://dx.doi.org/10.1161/HYPERTENSIONAHA.119.13017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6685737PMC
September 2019

Epithelial sodium channels in endothelial cells mediate diet-induced endothelium stiffness and impaired vascular relaxation in obese female mice.

Metabolism 2019 10 11;99:57-66. Epub 2019 Jul 11.

Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65212, USA; Department of Medicine, University of Missouri School of Medicine, Columbia, MO 65212, USA. Electronic address:

Objective: Mineralocorticoid receptor activation of the epithelial sodium channel in endothelial cells (ECs) (EnNaC) is accompanied by aldosterone induced endothelial stiffening and impaired nitric oxide (NO)-mediated arterial relaxation. Recent data support enhanced activity of the alpha subunit of EnNaC (αEnNaC) mediates this aldosterone induced endothelial stiffening and associated endothelial NO synthase (eNOS) activation. There is mounting evidence that diet induced obesity diminishes expression and activation of AMP-activated protein kinase α (AMPKα), sirtuin 1 (Sirt1), which would be expected to lead to impaired downstream eNOS activation. Thereby, we posited that enhanced EnNaC activation contributes to diet induced obesity related increases in stiffness of the endothelium and diminished NO mediated vascular relaxation by increasing oxidative stress and related inhibition of AMPKα, Sirt1, and associated eNOS inactivation.

Materials/methods: Sixteen to twenty week-old αEnNaC knockout (αEnNaC) and wild type littermate (EnNaC) female mice were fed a mouse chow or an obesogenic western diet (WD) containing excess fat (46%) and fructose (17.5%) for 16 weeks. Sodium currents of ECs, endothelial stiffness and NO mediated aortic relaxation were examined along with indices of aortic oxidative stress, vascular remodeling and fibrosis.

Results: Enhanced EnNaC activation-mediated WD-induced increases in sodium currents in isolated lung ECs, increased endothelial stiffness and impaired aortic endothelium-dependent relaxation to acetylcholine (10-10 mol/L). These abnormalities occurred in conjunction with WD-mediated aortic tissue oxidative stress, inflammation, and decreased activation of AMPKα, Sirt1, and downstream eNOS were substantially mitigated in αEnNaC mice. Importantly, αEnNaC prevented WD induced increases in endothelial stiffness and related impairment of endothelium-dependent relaxation as well as aortic fibrosis and remodeling. However, EnNaC signaling was not involved in diet-induced abnormal expression of adipokines and CYP11b2 in abdominal aortic perivascular adipose tissue.

Conclusion: These data suggest that endothelial specific EnNaC activation mediates WD-induced endothelial stiffness, impaired eNOS activation, aortic fibrosis and remodeling through increased aortic oxidative stress and increased inflammation related to a reduction of AMPKα and Sirt 1 mediated eNOS phosphorylation/activation and NO production.
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http://dx.doi.org/10.1016/j.metabol.2019.153946DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6901094PMC
October 2019

Mineralocorticoid antagonists and ENaC inhibitors in hyperaldosteronism.

J Clin Hypertens (Greenwich) 2019 07 6;21(7):929-931. Epub 2019 Jun 6.

Diabetes and Cardiovascular Center, Dalton Cardiovascular Research Center, VA Medical Center, University of Missouri School of Medicine, Columbia, Missouri.

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http://dx.doi.org/10.1111/jch.13566DOI Listing
July 2019

A Calcium Mediated Mechanism Coordinating Vascular Smooth Muscle Cell Adhesion During KCl Activation.

Front Physiol 2018 18;9:1810. Epub 2018 Dec 18.

Dalton Cardiovascular Research Center, Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States.

Efficient mechanotransduction in vascular smooth muscle cells (VSMCs) is intimately coupled to physical coupling of the cell to extracellular matrix proteins (ECM) by integrins. Integrin adhesion receptors are essential for normal vascular function and defective integrin signaling is associated with cardiovascular disease. However, less is known about the mechanism of integrin activation in VSMCs in relation to vasoregulation. Our laboratory previously demonstrated that the vasoconstrictor Angiotensin II increases VSMC stiffness in concert with enhanced adhesion to fibronectin (FN), indicating an important role for adhesion in contraction. However, the mechanism of this coordination remains to be clarified. In this study, intracellular Ca ([Ca]) was hypothesized to link integrin activation through inside-out signaling pathways leading to enhanced adhesion in response to AII. By using atomic force microscopy (AFM) with an anti-α antibody coated AFM probe, we confirmed that cell stiffness was increased by AII, while we observed no change in adhesion to an α integrin antibody. This indicated that increases in cell adhesion to FN induced by AII were occurring through an integrin activation process, as increased membrane integrin expression/receptor density would have been accompanied by increased adhesion to the anti-α antibody. Further studies were performed using either KCl or BAPTA-AM to modulate the level of [Ca]. After KCl, VSMCs showed a rapid transient increase in cell stiffness as well as cell adhesion to FN, and these two events were synchronized with superimposed transient increases in the level of [Ca] which was measured using the Ca indicator, fluo-4. These relationships were unaffected in VSMCs pretreated with the myosin light chain kinase inhibitor, ML-7. In contrast, unstimulated VSMCs incubated with an intracellular calcium chelator, BAPTA-AM, showed reduced cell adhesion to FN as well the expected decrease in [Ca]. These data suggest that in VSMCs, integrin activation is linked to signaling events tied to levels of [Ca] while being less dependent on events at the level of contractile protein activation. These findings provide additional evidence to support a role for adhesion in VSMC contraction and suggest that following cell contractile activation, that adhesion may be regulated in tandem with the contractile event.
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http://dx.doi.org/10.3389/fphys.2018.01810DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6305448PMC
December 2018

PAI-1 Exacerbates White Adipose Tissue Dysfunction and Metabolic Dysregulation in High Fat Diet-Induced Obesity.

Front Pharmacol 2018 26;9:1087. Epub 2018 Sep 26.

Drug Discovery Research Center, The School of Pharmacy, Southwest Medical University, Luzhou, China.

Plasminogen activator inhibitor (PAI)-1 levels and activity are known to increase during metabolic syndrome and obesity. In addition, previous studies have implicated PAI-1 in adipose tissue (AT) expansion while also contributing to insulin resistance. As inflammation is also known to occur in AT during obesity, we hypothesized that in a high-fat diet (HFD)-induced obese mouse model PAI-1 contributes to macrophage-mediated inflammation and metabolic dysfunction. Four- to five-weeks-old male C57B6/6J mice were fed a HFD (45%) for 14 weeks, while age-matched control mice were fed a standard laboratory chow diet (10% fat). Additional studies were performed in PAI-1 knockout mice and wild type mice treated with an inhibitor (PAI-039) of PAI-1. Macrophage polarization were measured by real time PCR. HFD mice showed increased expression of PAI-1 in visceral white AT (WAT) that also displayed increased macrophage numbers. PAI-1 deficient mice exhibited increased numbers of anti-inflammatory macrophages in WAT and were resistant to HFD-induced obesity. Similarly, pharmacological inhibition of PAI-1 using PAI-039 significantly decreased macrophage infiltration in WAT and improved metabolic status in HFD-induced wild-type mice. Importantly, the numbers of M1 macrophages appeared to be increased by the HFD and decreased by either genetic PAI-1 depletion or PAI-039 treatment. Collectively, our findings provide support for PAI-1 contributing to the development of inflammation in adipose tissue and explain the mechanism of inflammation modulated by PAI-1 in the disordered metabolism in HFD-induced obesity.
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http://dx.doi.org/10.3389/fphar.2018.01087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6169321PMC
September 2018

Epithelial Sodium Channel in Aldosterone-Induced Endothelium Stiffness and Aortic Dysfunction.

Hypertension 2018 09;72(3):731-738

From the Diabetes and Cardiovascular Research Center (G.J., J.H., A.R.A., A.W.-C., J.R.S.).

Enhanced activation of the endothelial mineralocorticoid receptor contributes to the development of arterial stiffness, which is an independent predictor of cardiovascular disease. Previously, we showed that enhanced endothelium mineralocorticoid receptor signaling in female mice prompts expression and translocation of the α-subunit of the epithelial sodium channel to the endothelial cell (EC) surface (EnNaC) inducing vascular fibrosis and stiffness. Further, amiloride, an epithelial sodium channel antagonist, inhibits vascular fibrosis, remodeling, and stiffness induced by feeding a Western diet high in saturated fat and refined carbohydrates. However, how this occurs remains unknown. Thereby, we hypothesized that endothelial cell-specific EnNaC activation is necessary for aldosterone-mediated endothelium stiffness. To address this notion, EnNaC α-subunit knockout (EnNaC) and wild-type littermate female mice were administrated aldosterone (250 µg/kg per day) via osmotic minipumps for 3 weeks beginning at 25 to 28 weeks of age. In isolated mouse endothelial cells, inward sodium currents were significantly reduced in amiloride controls, as well as in EnNaC. Likewise, aldosterone-induced endothelium stiffness was increased and endothelium-dependent relaxation less in EnNaC versus wild-type. Further, EnNaC mice exhibited attenuated responses to aldosterone infusion, including aortic endoplasmic reticulum stress, endothelium nitric oxide synthase activation, endothelium permeability, expression of proinflammatory cytokines, oxidative stress, and aortic collagen 1 deposition, supporting the notion that αEnNaC subunit activation contributes to these vascular responses.
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.118.11339DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6202124PMC
September 2018

TRPV4 increases cardiomyocyte calcium cycling and contractility yet contributes to damage in the aged heart following hypoosmotic stress.

Cardiovasc Res 2019 01;115(1):46-56

Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 1 Hospital Drive, Columbia, MO, USA.

Aims: Cardiomyocyte Ca2+ homeostasis is altered with aging via poorly-understood mechanisms. The Transient Receptor Potential Vanilloid 4 (TRPV4) ion channel is an osmotically-activated Ca2+ channel, and there is limited information on the role of TRPV4 in cardiomyocytes. Our data show that TRPV4 protein expression increases in cardiomyocytes of the aged heart. The objective of this study was to examine the role of TRPV4 in cardiomyocyte Ca2+ homeostasis following hypoosmotic stress and to assess the contribution of TRPV4 to cardiac contractility and tissue damage following ischaemia-reperfusion (I/R), a pathological condition associated with cardiomyocyte osmotic stress.

Methods And Results: TRPV4 protein expression increased in cardiomyocytes of Aged (24-27 months) mice compared with Young (3-6 months) mice. Immunohistochemistry revealed TRPV4 localization to microtubules and the t-tubule network of cardiomyocytes of Aged mice, as well as in left ventricular myocardium of elderly patients undergoing surgical aortic valve replacement for aortic stenosis. Following hypoosmotic stress, cardiomyocytes of Aged, but not Young exhibited an increase in action-potential induced Ca2+ transients. This effect was mediated via increased sarcoplasmic reticulum Ca2+ content and facilitation of Ryanodine Receptor Ca2+ release and was prevented by TRPV4 antagonism (1 μmol/L HC067047). A similar hypoosmotic stress-induced facilitation of Ca2+ transients was observed in Young transgenic mice with inducible TRPV4 expression in cardiomyocytes. Following I/R, isolated hearts of Young mice with transgenic TRPV4 expression exhibited enhanced contractility vs. hearts of Young control mice. Similarly, hearts of Aged mice exhibited enhanced contractility vs. hearts of Aged TRPV4 knock-out (TRPV4-/-) mice. In Aged, pharmacological inhibition of TRPV4 (1 μmol/L, HC067047) prevented hypoosmotic stress-induced cardiomyocyte death and I/R-induced cardiac damage.

Conclusions: Our findings provide a new mechanism for hypoosmotic stress-induced cardiomyocyte Ca2+ entry and cell damage in the aged heart. These finding have potential implications in treatment of elderly populations at increased risk of myocardial infarction and I/R injury.
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http://dx.doi.org/10.1093/cvr/cvy156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6302264PMC
January 2019

Alpha -adrenergic stimulation selectively enhances endothelium-mediated vasodilation in rat cremaster arteries.

Physiol Rep 2018 05;6(9):e13703

Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.

We have systematically investigated how vascular smooth muscle α -adrenoceptor activation impacts endothelium-mediated vasodilation in isolated, myogenically active, rat cremaster muscle 1A arteries. Cannulated cremaster arteries were pressurized intraluminally to 70 mmHg to induce myogenic tone, and exposed to vasoactive agents via bath superfusion at 34°C. Smooth muscle membrane potential was measured via sharp microelectrode recordings in pressurized, myogenic arteries. The α -adrenergic agonist phenylephrine (25-100 nmol/L) produced further constriction of myogenic arteries, but did not alter the vasorelaxant responses to acetylcholine (0.3 μmol/L), SKA-31 (an activator of endothelial Ca -dependent K channels) (3 μmol/L) or sodium nitroprusside (10 μmol/L). Exposure to 0.25-1 μmol/L phenylephrine or 1 μmol/L norepinephrine generated more robust constrictions, and also enhanced the vasodilations evoked by acetylcholine and SKA-31, but not by sodium nitroprusside. In contrast, the thromboxane receptor agonist U46619 (250 nmol/L) dampened responses to all three vasodilators. Phenylephrine exposure depolarized myogenic arteries, and mimicking this effect with 4-aminopyridine (1 mmol/L) was sufficient to augment the SKA-31-evoked vasodilation. Inhibition of L-type Ca channels by 1 μmol/L nifedipine decreased myogenic tone, phenylephrine-induced constriction and prevented α -adrenergic enhancement of endothelium-evoked vasodilation; these latter deficits were overcome by exposure to 3 and 10 μmol/L phenylephrine. Mechanistically, augmentation of ACh-evoked dilation by phenylephrine was dampened by eNOS inhibition and abolished by blockade of endothelial KCa channels. Collectively, these data suggest that increasing α -adrenoceptor activation beyond a threshold level augments endothelium-evoked vasodilation, likely by triggering transcellular signaling between smooth muscle and the endothelium. Physiologically, this negative feedback process may serve as a "brake" to limit the extent of vasoconstriction in the skeletal microcirculation evoked by the elevated sympathetic tone.
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http://dx.doi.org/10.14814/phy2.13703DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5949301PMC
May 2018

Arteriolar vasodilation involves actin depolymerization.

Am J Physiol Heart Circ Physiol 2018 08 4;315(2):H423-H428. Epub 2018 May 4.

Dalton Cardiovascular Research Center and Department of Medical Pharmacology and Physiology, University of Missouri , Columbia, Missouri.

It is generally assumed that relaxation of arteriolar vascular smooth muscle occurs through hyperpolarization of the cell membrane, reduction in intracellular Ca concentration, and activation of myosin light chain phosphatase/inactivation of myosin light chain kinase. We hypothesized that vasodilation is related to depolymerization of F-actin. Cremaster muscles were dissected in rats under pentobarbital sodium anesthesia (50 mg/kg). First-order arterioles were dissected, cannulated on glass micropipettes, pressurized, and warmed to 34°C. Internal diameter was monitored with an electronic video caliper. The concentration of G-actin was determined in flash-frozen intact segments of arterioles by ultracentrifugation and Western blot analyses. Arterioles dilated by ~40% of initial diameter in response to pinacidil (1 × 10 mM) and sodium nitroprusside (5 × 10 mM). The G-actin-to-smooth muscle 22α ratio was 0.67 ± 0.09 in arterioles with myogenic tone and increased significantly to 1.32 ± 0.34 ( P < 0.01) when arterioles were dilated with pinacidil and 1.14 ± 0.18 ( P < 0.01) with sodium nitroprusside, indicating actin depolymerization. Compared with control vessels (49 ± 5%), the percentage of phosphorylated myosin light chain was significantly reduced by pinacidil (24 ± 2%, P < 0.01) but not sodium nitroprusside (42 ± 4%). These findings suggest that actin depolymerization is an important mechanism for vasodilation of resistance arterioles to external agonists. Furthermore, pinacidil produces smooth muscle relaxation via both decreases in myosin light chain phosphorylation and actin depolymerization, whereas sodium nitroprusside produces smooth muscle relaxation primarily via actin depolymerization. NEW & NOTEWORTHY This article adds to the accumulating evidence on the contribution of the actin cytoskeleton to the regulation of vascular smooth muscle tone in resistance arterioles. Actin depolymerization appears to be an important mechanism for vasodilation of resistance arterioles to pharmacological agonists. Dilation to the K channel opener pinacidil is produced by decreases in myosin light chain phosphorylation and actin depolymerization, whereas dilation to the nitric oxide donor sodium nitroprusside occurs primarily via actin depolymerization.
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http://dx.doi.org/10.1152/ajpheart.00723.2017DOI Listing
August 2018

Chronic interval exercise training prevents BK channel-mediated coronary vascular dysfunction in aortic-banded miniswine.

J Appl Physiol (1985) 2018 07 29;125(1):86-96. Epub 2018 Mar 29.

Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri.

Conventional treatments have failed to improve the prognosis of heart failure with preserved ejection fraction (HFpEF) patients. Thus, the purpose of this study was to determine the therapeutic efficacy of chronic interval exercise training (IT) on large-conductance Ca-activated K (BK) channel-mediated coronary vascular function in heart failure. We hypothesized that chronic interval exercise training would attenuate pressure overload-induced impairments to coronary BK channel-mediated function. A translational large-animal model with cardiac features of HFpEF was used to test this hypothesis. Specifically, male Yucatan miniswine were divided into three groups ( n = 7/group): control (CON), aortic banded (AB)-heart failure (HF), and AB-interval trained (HF-IT). Coronary blood flow, vascular conductance, and vasodilatory capacity were measured after administration of the BK channel agonist NS-1619 both in vivo and in vitro in the left anterior descending coronary artery and isolated coronary arterioles, respectively. Skeletal muscle citrate synthase activity was decreased and left ventricular brain natriuretic peptide levels increased in HF vs. CON and HF-IT animals. A parallel decrease in NS-1619-dependent coronary vasodilatory reserve in vivo and isolated coronary arteriole vasodilatory responsiveness in vitro were observed in HF animals compared with CON, which was prevented in the HF-IT group. Although exercise training prevented BK channel-mediated coronary vascular dysfunction, it did not change BK channel α-subunit mRNA, protein, or cellular location (i.e., membrane vs. cytoplasm). In conclusion, these results demonstrate the viability of chronic interval exercise training as a therapy for central and peripheral adaptations of experimental heart failure, including BK channel-mediated coronary vascular dysfunction. NEW & NOTEWORTHY Conventional treatments have failed to improve the prognosis of heart failure with preserved ejection fraction (HFpEF) patients. Our findings show that chronic interval exercise training can prevent BK channel-mediated coronary vascular dysfunction in a translational swine model of chronic pressure overload-induced heart failure with relevance to human HFpEF.
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http://dx.doi.org/10.1152/japplphysiol.01138.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6086974PMC
July 2018

Depletion of dendritic cells in perivascular adipose tissue improves arterial relaxation responses in type 2 diabetic mice.

Metabolism 2018 08 9;85:76-89. Epub 2018 Mar 9.

Dalton Cardiovascular Research Center, University of Missouri and Truman VA Medical Center, Columbia, MO 65211, USA; Department of Medical Pharmacology and Physiology, University of Missouri and Truman VA Medical Center, Columbia, MO 65211, USA. Electronic address:

Background: Accumulation of multiple subtypes of immune cells in perivascular adipose tissue (PVAT) has been proposed to cause vascular inflammation and dysfunction in type 2 diabetes (T2DM). This study was designed to investigate specific roles for dendritic cells in PVAT in the development of vascular inflammation and impaired PVAT-mediated vasorelaxation in T2DM.

Methods And Results: Studies were performed using db/db mice (model of T2DM) and their Db heterozygote (DbHET), lean and normoglycemic controls. Dendritic cell depletion was performed by cross-breeding DbHet with Flt3l (null for ligand for FMS-kinase tyrosine kinase) mice. Using PCR, it was found that the majority of dendritic cells (CD11c) were located in PVAT rather than the vascular wall. Flow cytometry similarly showed greater dendritic cell accumulation in adipose tissue from db/db mice than DbHET controls. Adipose tissue from db/db mice displayed increased mRNA levels of proinflammatory cytokines TNF-α and IL-6 and decreased mRNA levels of the anti-inflammatory mediator adiponectin, compared to DbHET mice. Depletion of dendritic cells in db/db (confirmed by flow cytometry) reduced TNF-α and IL-6 mRNA levels in diabetic adipose tissue without influencing adiponection expression. Moreover, in mesenteric arteries, dendritic cell depletion improved the ability of PVAT to augment acetylcholine-induced vasorelaxation and anti-contractile activity.

Conclusions: In a murine model of T2DM, dendritic cells accumulated predominantly in PVAT, as opposed to the vessel wall, per se. Accumulation of dendritic cells in PVAT was associated with overproduction of pro-inflammatory cytokines, which contributed to an impaired ability of PVAT to augment vasorelaxation and exert anti-contractile activity in T2DM.
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http://dx.doi.org/10.1016/j.metabol.2018.03.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6062442PMC
August 2018

Diabetic Cardiomyopathy: An Update of Mechanisms Contributing to This Clinical Entity.

Circ Res 2018 02;122(4):624-638

From the Diabetes and Cardiovascular Research Center (G.J., J.R.S.) and Department of Medical Pharmacology and Physiology (M.A.H., J.R.S.), University of Missouri School of Medicine, Columbia; Dalton Cardiovascular Research Center, University of Missouri, Columbia (M.A.H., J.R.S.); and Research Service, Truman Memorial Veterans Hospital, Columbia, MO (G.J., J.R.S.).

Heart failure and related morbidity and mortality are increasing at an alarming rate, in large part, because of increases in aging, obesity, and diabetes mellitus. The clinical outcomes associated with heart failure are considerably worse for patients with diabetes mellitus than for those without diabetes mellitus. In people with diabetes mellitus, the presence of myocardial dysfunction in the absence of overt clinical coronary artery disease, valvular disease, and other conventional cardiovascular risk factors, such as hypertension and dyslipidemia, has led to the descriptive terminology, diabetic cardiomyopathy. The prevalence of diabetic cardiomyopathy is increasing in parallel with the increase in diabetes mellitus. Diabetic cardiomyopathy is initially characterized by myocardial fibrosis, dysfunctional remodeling, and associated diastolic dysfunction, later by systolic dysfunction, and eventually by clinical heart failure. Impaired cardiac insulin metabolic signaling, mitochondrial dysfunction, increases in oxidative stress, reduced nitric oxide bioavailability, elevations in advanced glycation end products and collagen-based cardiomyocyte and extracellular matrix stiffness, impaired mitochondrial and cardiomyocyte calcium handling, inflammation, renin-angiotensin-aldosterone system activation, cardiac autonomic neuropathy, endoplasmic reticulum stress, microvascular dysfunction, and a myriad of cardiac metabolic abnormalities have all been implicated in the development and progression of diabetic cardiomyopathy. Molecular mechanisms linked to the underlying pathophysiological changes include abnormalities in AMP-activated protein kinase, peroxisome proliferator-activated receptors, O-linked N-acetylglucosamine, protein kinase C, microRNA, and exosome pathways. The aim of this review is to provide a contemporary view of these instigators of diabetic cardiomyopathy, as well as mechanistically based strategies for the prevention and treatment of diabetic cardiomyopathy.
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http://dx.doi.org/10.1161/CIRCRESAHA.117.311586DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5819359PMC
February 2018

Interaction of IL-6 and TNF-α contributes to endothelial dysfunction in type 2 diabetic mouse hearts.

PLoS One 2017 2;12(11):e0187189. Epub 2017 Nov 2.

Department of Health and Human Performance, University of Houston, Houston, Texas, United States of America.

Objectives: Inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), are individually considered as important contributors to endothelial dysfunction in obesity and type 2 diabetes (T2D). However, their interactions in coronary arteriole endothelial dysfunction are uncertain. Therefore, this study aimed to determine the effects of TNF-α and IL-6 interactions on coronary endothelial dysfunction in experimental T2D.

Methods: The studies used wild type (WT), diabetic mice (db/db), db/db null for TNF (dbTNF-/dbTNF-), and db/db mice treated with neutralizing antibody to IL-6 (anti-IL-6). Endothelium-dependent (acetylcholine [ACh], or luminal flow-induced shear stress) and endothelium-independent (sodium nitroprusside [SNP]) vasodilation of isolated and pressurized coronary arterioles were determined. Quantitative PCR, Western blot, and immunofluorescence staining were utilized for mechanistic studies.

Results: Relative to WT, arteriolar dilation to both ACh and flow was attenuated in db/db mice and dbTNF-/dbTNF-. Treatment of dbTNF-/dbTNF- and db/db mice with anti-IL-6 improved arteriolar dilation compared to db/db mice. Immunofluorescence staining illustrated localization of IL-6 within the endothelial cells of coronary arterioles. In db/db mice, mRNA and protein expression of IL-6 and superoxide (O2-) production were higher, but reduced by anti-IL-6 treatment. Also, in db/db mice, mRNA and protein expression of TNF-α suppressed by the anti-IL-6 treatment and the reduced expression of mRNA and protein expression of IL-6 by the genetic deletion of TNF-α both supported a reciprocal regulation between TNF-α and IL-6. Superoxide dismutase 2 (SOD2) expression and phosphorylation of eNOS (p-eNOS/eNOS) were lower in db/db mice coronary arterioles and were restored in db/db+Anti-IL-6 and dbTNF-/dbTNF- mice.

Conclusion: The interactions between TNF-α and IL-6 exacerbate oxidative stress and reduce phosphorylation of eNOS, thereby contributing to coronary endothelial dysfunction in T2D mice.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0187189PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5667841PMC
December 2017

Angiotensin II Type 1 Receptor Mechanoactivation Involves RGS5 (Regulator of G Protein Signaling 5) in Skeletal Muscle Arteries: Impaired Trafficking of RGS5 in Hypertension.

Hypertension 2017 12 23;70(6):1264-1272. Epub 2017 Oct 23.

From the Department of Medical Pharmacology and Physiology (K.H., M.L., G.A.M., M.A.H.) and Dalton Cardiovascular Research Center (K.H., Z.N., G.A.M., M.A.H.), University of Missouri, Columbia; and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville (K.H.).

Studies suggest that arteriolar pressure-induced vasoconstriction can be initiated by GPCRs (G protein-coupled receptors), including the ATR (angiotensin II type 1 receptor). This raises the question, are such mechanisms regulated by negative feedback? The present studies examined whether RGS (regulators of G protein signaling) proteins in vascular smooth muscle cells are colocalized with the ATR when activated by mechanical stress or angiotensin II and whether this modulates ATR-mediated vasoconstriction. To determine whether activation of the ATR recruits RGS5, an in situ proximity ligation assay was performed in primary cultures of cremaster muscle arteriolar vascular smooth muscle cells treated with angiotensin II or hypotonic solution in the absence or presence of candesartan (an ATR blocker). Proximity ligation assay results revealed a concentration-dependent increase in trafficking/translocation of RGS5 toward the activated ATR, which was attenuated by candesartan. In intact arterioles, knockdown of RGS5 enhanced constriction to angiotensin II and augmented myogenic responses to increased intraluminal pressure. Myogenic constriction was attenuated to a higher degree by candesartan in RGS5 siRNA-transfected arterioles, consistent with RGS5 contributing to downregulation of ATR-mediated signaling. Further, translocation of RGS5 was impaired in vascular smooth muscle cells of spontaneously hypertensive rats. This is consistent with dysregulated (RGS5-mediated) ATR signaling that could contribute to excessive vasoconstriction in hypertension. In intact vessels, candesartan reduced myogenic vasoconstriction to a greater extent in spontaneously hypertensive rats compared with controls. Collectively, these findings suggest that ATR activation results in translocation of RGS5 toward the plasma membrane, limiting ATR-mediated vasoconstriction through its role in G protein-dependent signaling.
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.117.09757DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5683087PMC
December 2017

Enhanced endothelium epithelial sodium channel signaling prompts left ventricular diastolic dysfunction in obese female mice.

Metabolism 2018 01 8;78:69-79. Epub 2017 Sep 8.

Diabetes and Cardiovascular Research Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA; Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO 65212, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65212, USA. Electronic address:

Objective: Enhanced activation of cell specific mineralocorticoid receptors (MRs) in obesity plays a key role in the development of cardiovascular disease including cardiac diastolic dysfunction as a critical prognosticator. Our previous investigations demonstrated that selective endothelium MR activation promotes a maladaptive inflammatory response and fibrosis in cardiovascular tissue in female mice fed a western diet (WD), and this was associated with expression and activation of the epithelial sodium channel on the surface of endothelial cells (EnNaC). However, the specific role of EnNaC signaling in the development of cardiac stiffness and diastolic dysfunction has not been examined. We hypothesized that targeted inhibition of EnNaC with low dose amiloride would prevent WD-induced diastolic dysfunction by suppressing abnormal endothelial permeability, inflammation and oxidative stress, and myocardial fibrosis.

Materials/methods: Four week-old female C57BL6/J mice were fed a WD with or without a low dose of amiloride (1mg/kg/day) for 16weeks. Left ventricular cardiac function was evaluated by magnetic resonance imaging. In addition, we examined coronary vessel and cardiac remodeling, fibrosis, macrophage infiltration using immunohistochemistry, western blot and real time PCR.

Results: Amiloride, an antagonist of EnNaC, attenuated WD-induced impairment of left ventricular initial filling rate and relaxation time. Cardiac diastolic dysfunction was associated with increases in coronary endothelium remodeling and permeability that paralleled WD-induced increases in F-actin and fibronectin, decreased expression of claudin-5 and occludin, and increased macrophage recruitment, M1 polarization, cardiac oxidative stress, fibrosis and maladaptive remodeling.

Conclusion: Our data support the concept that EnNaC activation mediates endothelium permeability which, in turn, promotes macrophage infiltration, M1 polarization, and oxidative stress, resulting in cardiac fibrosis and diastolic dysfunction in females with diet induced obesity.
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http://dx.doi.org/10.1016/j.metabol.2017.08.008DOI Listing
January 2018

N-Cadherin, a novel and rapidly remodelling site involved in vasoregulation of small cerebral arteries.

J Physiol 2017 03 7;595(6):1987-2000. Epub 2017 Feb 7.

Dalton Cardiovascular Research Center, Columbia, MO, USA.

Key Points: N-cadherin formed punctate adherens junctions (AJ) along the borders between vascular smooth muscle cells (VSMCs) in the pressurized rat superior cerebellar artery. The formation of N-cadherin AJs in the vessel wall depends on the intraluminal pressure and was responsive to treatment with phenylephrine (PE) (10  m) and ACh (10  m). N-cadherin-coated beads were able to induce clustering of N-cadherin-enhanced green fluorescent protein (EGFP) on the plasma membrane of isolated VSMCs, whereas treatment with PE (10  m) or sodium nitroprusside (10  m) induced a significant increase or decrease in the N-cadherin-EGFP clustering, respectively. Application of pulling force (∼1 nN) to the N-cadherin-coated beads via an atomic force microscope induced a localized mechanical response from the VSMCs that opposed the pulling.

Abstract: N-cadherin is the major cell-cell adhesion molecule in vascular smooth muscle cells (VSMCs). We tested the hypothesis that N-cadherin is part of a novel mechanosensory mechanism in VSMCs and plays an active role in both the arteriolar myogenic response and during changes in vascular tone induced by vasomotor agonists. Intact and pressurized rat superior cerebellar arteries were labelled for confocal immunofluorescence imaging. N-cadherin formed punctate adherens junctions (AJ) along the borders between VSMCs. When the lumen pressure was raised from 50 to 90 mmHg, both the density and the average size of N-cadherin AJs increased significantly. Similarly, arteriolar constriction with phenylephrine (PE) (10  m) induced a significant increase of N-cadherin AJ density at 50 mmHg, whereas vasodilatation induced by ACh (10  m) was accompanied by a significant decrease in density and size of N-cadherin AJs. An atomic force microscope (AFM) was employed to further examine the mechano-responsive properties of N-cadherin adhesion sites in isolated VSMCs. AFM probes with an attached N-cadherin-coated microbead (5 μm) induced a progressive clustering of N-cadherin-enhanced green fluorescent protein (EGFP) on the VSMC surface. Application of pulling force (∼1 nN) to the N-cadherin-coated-beads with the AFM induced a localized mechanical response from the VSMCs that opposed the pulling. Treatment with PE (10  m) or sodium nitroprusside (10  m) induced a significant increase or decrease of the N-cadherin-EGFP clustering, respectively. These observations provide compelling evidence that N-cadherin AJs are sensitive to pressure and vasomotor agonists in VSMCs and support a functional role of N-cadherin AJs in vasomotor regulation.
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http://dx.doi.org/10.1113/JP272995DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5350452PMC
March 2017