bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of metabolism‐perfusion matching in a heterogeneous microvascular network
Authors: Roy Tuhin K , Joyner Michael J , Secomb Timothy W
Published: June 2021

Microvascular blood flow regulation involves multiple mechanisms designed to maintain adequate perfusion under conditions of varying metabolic demand. The impact of various regulatory factors on metabolism‐perfusion matching was assessed using a heterogeneous microvascular network model that accounted for myogenic, shear, and metabolic flow regulation. Estimates of oxygen extraction under control conditions were compared to an increase in tissue oxygen consumption in combination with a reduction in perfusion. For the values of parameters used, overall oxygen extraction was increased by a factor of 7.19 with a tenfold increase in consumption and a factor of 1.47 when perfusion was reduced by 50%. Combining increased consumption with decreased flow resulted in an increase in extraction by a factor of 9.20 compared to control, suggesting that network regulatory capacity remained intact under these conditions. This has significant implications for the optimization of metabolism‐perfusion matching, since impairment of flow regulation under conditions of increased consumption and decreased perfusion can lead to microvascular perfusion heterogeneity and cause organ failure in critically ill patients.
Cellular mechanism and computational modeling of the conductive arterial hyperpolarization/dilation
Authors: Jiang Zhi‐Gen , Chen Fang‐Yi , Ma Ke‐Tao
Published: June 2021

Evoked focal hyperpolarization and dilation (e.g., by ACh) can conduct along a small artery thus activate a fast blood flow surge; but the mechanism for such conduction remains unclear. Using intracellular and whole‐cell recording of guinea pig arterial cells and mathematical modeling, we found: (1) The resting potentials (RP) of sampled cells showed a bimodal distribution peaked near −75 and −40 mV. A cell initially having a low RP may swiftly shift to a high RP state and vice versa. Such shifts between the two RP levels were mimicked by wash‐in and ‐out of Ba2+ (≤100 μM). Whole‐cell I/V showed an inward rectification that was sensitive to [K+]o and Ba2+. (2) ACh induced a robust hyperpolarization or outward current at ~−40 mV, that was blocked by a 18β‐glycyrrhetinic acid plus Ba2+in smooth muscle cells. (3) Data of dual cell recording and cell labeling indicated a gap junction coupling among the vessel cells. (4) Whole‐cell I/V curves of dispersed cells could be math‐modeled by a sum of two voltage‐dependent (Kir, KDR) and three voltage‐independent ion currents. (5) Inputting the five currents’ conductance means and their random variations into GHK zero‐current equation, and letting our custom‐written software seek individual RPs, we reproduced a bimodal RP distribution peaked near −75 and −40 mV. With timed alteration of ion conductances, the computation also simulated regenerative fast RP shift between the two RP levels. We conclude: 1) The arterial cells express abundant inward rectifier K+‐channels (Kir), which critically underlies the regenerative RP shift due to its unique voltage dependency. 2) Together with the gap junction coupling and Na‐K‐pump energy replenishing mechanism, the artery satisfies the minimal requisites for non‐decay conduction of the hyperpolarization/dilation. Supported by grant of NIH NIDCD DC004716.
Effect of systemic hematocrit on volume flow and cell free layer width in arterioles
Authors: Gorski Steven E. , Yalcin Ozlem , Jivani Manoj , Intaglietta Marcos , Johnson Paul C.
Published: June 2021

The effect of hematocrit on effective viscosity is well known for in vitro systems but the effect in vivo is less clear due to the formation of a cell free layer (CFL) at the vascular wall that may influence vascular tone. The CFL and volumetric flow rate (Q) were assessed in rat cremaster arterioles (20–40 μm) during systemic hemodilution and hemoconcentration. Systemic hematocrit (Hctsys) was increased stepwise by 5% from 40 to 75% during hemoconcentration and decreased by 5% from 40 to 20% during hemodilution. The CFL was measured with a high speed video camera and custom built software. Velocity and vessel diameter measurements were obtained from the video files using a dual‐window cross correlation technique and calipers. The CFL values were 5.4± 0.2, 3.1±0.1 and 0.9±0.1 μm at 20, 40 and 75% Hctsys, respectively. The Q values were 14.5, 9.0±0.6 and 4.9±0.4 nl/sec at 20, 40 and 75% Hctsys, respectively. Overall, Q decreased 66% from 20 to 75% Hctsys. The vessel diameter did not change significantly as Hctsys was reduced from 40% to 20% and from 75 to 40%. The arterial pressure was 17% higher at 40% and 32% higher at 75% as compared to 20% Hctsys. The flow change was inversely proportionate to Hctsys change when corrected for differences in arterial pressure. Apparently the change in CFL width did not induce vascular responses in these vessels due to simultaneous changes in other factors.
Cellular Mechanisms of Hydrogen Peroxide (H2O2)‐induced Permeability Increases in Intact Venules: Role of H2O2‐induced Ca2+‐independent Nitric Oxide (NO) Production in Endothelial Cells
Authors: Zhou Xueping , He Pingnian
Published: June 2021

H2O2 has been known to increase NO production contributing to vasodilation in arterioles, but its role in venular microvessel permeability remains unknown. We previously showed that H2O2 induced delayed but progressive increases in EC [Ca2+]i, hydraulic conductivity (Lp), and cell apoptosis in intact venules. This study aims to explore the signaling mechanisms of H2O2‐induced Lp increases with focus on H2O2‐induced NO production in ECs of venular walls. NO and EC [Ca2+]i were measured in DAF‐2 and Fura‐2 loaded vessels and permeability was determined by Lp measurements in rat venules. H2O2 (10 μM) induced an immediate increase in NO and reached a plateau (9.1±0.4 times that of control) after 45 min, which occurred prior to the increases in EC [Ca2+]i and not affected by Ca2+influx inhibitor LaCl3 (50 μM). Immunostaining for nitrotyrosine using confocal microscopy revealed extensive tyrosine nitration in vessels exposed to H2O2 for 2h but not in untreated vessels. Blocking H2O2‐induced NO production with L‐NMMA not only abolished H2O2‐induced delayed increases in EC [Ca2+]i and tyrosine nitration, but also prevented the Lp increases. Our results indicate that H2O2 activates endothelial NOS via a Ca2+ independent pathway and the excessive NO production and subsequent peroxynitrite formation‐mediated protein nitration may be the key for EC Ca2+ overload, resulting in cell injury and Lp increases. Supported by HL56237 and HL084338.
Systemic Clearance of Fluorescent Dextrans after Hemorrhage in Rats
Authors: Carvalho Helena , Woodruff Aleesha R , Simmons Kristin L , Pittman Roland N
Published: June 2021

An intact endothelial glycocalyx is associated with vascular homeostasis, and its disruption leads to increased vascular permeability. We evaluated the systemic clearance of macromolecules from the circulation after hemorrhage. We injected a dextran mixture (0.5ml of 1.2 mg/ml FITC‐labelled 500 kDa dextran (Dex‐500) and 0.5 ml of 2.5 mg/ml Texas Red‐labelled 40 kDa dextran (Dex‐40)) i.v. in anesthetized Sprague‐Dawley rats (250–350 g). Hemorrhage was induced by withdrawing 40% of blood volume over a 30 min period. After 30 min of stabilization at the end of hemorrhage, rats received the dextran mixture (1 ml/300 g rat). Blood samples were collected at 1, 5, 10, 15, 20 and 30 min and then centrifuged. Plasma fluorescence was analyzed in a luminescence spectrometer at 490/535 nm (ex/em) for Dex‐500 and 595/615 nm (ex/em) for Dex‐40. Hemorrhage led to a drop in arterial pressure from 110 ± 10 mmHg to 50 ± 8 mmHg. The clearance rate of Dex‐40 increased by 33% and Dex‐500 by 9% compared with the control group. Under control conditions Dex‐40/Dex‐500 clearance ratio was 1.36 and increased to 1.66 after hemorrhage; thus, the permeability to Dex‐40 increased more than the permeability to Dex‐500 following hemorrhage. The increased clearance rates of these macromolecules are consistent with degradation of the glycocalyx following hemorrhage, compared to control, based on its role as a permeability barrier to macromolecules.

Support: HL079087 from NHLBI
Role of endothelial surface layer in mediation of flow‐induced dilation of isolated arterioles
Authors: Marki Alex , Gara Edit , Veresh Zoltan , Seress Laszlo , Toth Peter , Koller Akos
Published: June 2021

Vascular endothelial cells respond to increases in wall shear stress (WSS) by releasing vasoactive factors. However, it is less known how WSS signal is sensed by the endothelial cells. Recent studies implied that the endothelial surface layer (ESL) senses changes in WSS and transmits the signal towards intracellular enzymes responsible for producing these factors. We hypothesized that degradation of ESL inhibits flow‐induced dilation of arterioles. Thus the effect of step‐wise increases in intraluminal flow were investigated on the diameter of isolated gracilis muscle arterioles of rats (passive diameter ~200μm, active diameter ~150μm) in the absence and presence of intraluminal hyaluronidase (1.5 and 15 U/ml, for 30 minutes) known to degrade hyaluronic acid of the ESL. In control conditions acetylcholine (ACh) and flow elicited dilations (20±6% and 20±2%, respectively). Presence of 1.5 U/ml hyaluronidase reduced ACh‐induced dilations, but did not affect flow‐induced responses. In contrast, 15 U/ml hyaluronidase elicited significant reduction of both Ach‐ and flow‐induced dilations (to 7±2% and to 2±1%), whereas vasomotor responses of smooth muscle remain intact. These results provide further support for the potential role of the ESL in sensing and transmitting changes in WSS.

(Grants: Hungarian Nat. Sci. Res. Fund.‐OTKA K71591, K67984, AHA Founders Aff., 0855910D)
Sphingosine 1‐Phosphate (S1P) Prevents Platelet Activating Factor (PAF)‐ Induced Permeability Increases by Activation of Rac‐1 Signaling in Intact Venules
Authors: Zhang Gengqian , Zhou Xueping , He Pingnian
Published: June 2021

S1P has been shown to enhance endothelial (EC) barrier function in vitro and prevent hyperpermeability in vivo. Our present study aims to identify the signaling mechanisms of S1P in regulation of microvessel permeability in intact microvessels using combined permeability measurements with confocal vascular structural analysis. Microvessel permeability was determined by measuring hydraulic conductivity (Lp). Rac‐1‐dependent signaling was examined using Rac 1 inhibitor NSC23766 (NSC, 200 μM). NO was measured in DAF‐2 loaded microvessels. EC gap formation and changes in VE‐cadherin was examined with confocal microscopy using fluorescence microspheres or antibody staining. Results showed that preperfusing vessels with S1P abolished PAF‐induced gap formation and VE‐cadherin redistribution without affecting PAF‐induced increases in EC [Ca2+]i and NO production. Perfusing vessels with NSC did not affect basal Lp and VE‐cadherin but abolished the inhibition of S1P on PAF‐induced Lp increases, EC gap formation, and VE‐cadherin disruption. In the presence of NSC and S1P, the peak Lp in response to PAF was restored to 7.2 ± 2 times that of the control and VE‐cadherin showed no significant difference from that with PAF alone. These results provide the first evidence in intact microvessels that S1P inhibits permeability increases by Rac1 signaling on EC AJ, which is either downstream from or independent of the initial EC Ca2+ and NO signaling pathways. Supported by HL56237 and HL084338.
Sphingosine‐1‐phosphate (S1P) attenuation of acute inflammatory response versus reactive oxygen generation in rat microvessels
Authors: Adamson R H , Sarai R K , Altangerel A , Clark J F , Curry F E
Published: June 2021

S1P activates Rac1, stabilizes peripheral actin and modulates permeability responses in intact microvessels. Previous results indicate that S1P (1 μM) inhibits 65% of the peak Lp response to bradykinin (Bk; 10 nM) in rat mesenteric microvessels. In contrast to the protective action of Rac1 above, activated Rac1 also regulates reactive oxygen species (ROS) generation via NADPH oxidase. Further, ROS may mediate Rac1 induced loss of cell‐cell adhesion in endothelium and could increase permeability. Thus we hypothesized that ROS scavenging could enhance S1P dependent permeability inhibition. To test this idea we perfused rat mesenteric microvessels with the ROS scavenger N‐(2‐Mercaptopropionyl)glycine (MPG; 500 μM), and compared the Lp response to Bk (10 nM) in the presence of MPG versus the presence of MPG and S1P (1 μM). The attenuation of the Bk response with S1P in the presence of MPG (to 0.32 ± 0.07, n=8) was not different from the level of attenuation seen in the absence of MPG indicating that ROS generation by S1P does not contribute to vessel Lp increase under these conditions. MPG (w/o S1P) enhanced the Bk response near 2‐fold, suggesting that a low level of ROS present in the tissue decreases the NO‐dependent Bk response via NO destruction. The results are consistent with the hypothesis that S1P acts predominantly though Rac1 activation to strengthen cell‐cell adhesion. Supp NIH HL28607.
Sex‐dependent influence of insulin (regular and fast) on in vivo albumin and protein clearance
Authors: Bingaman Susan , Huxley Virginia H
Published: June 2021

We have shown previously that the mechanisms whereby males and females achieve volume homeostasis differs and that sex influences vascular leak in response to porcine insulin. Whether regular (Novolin R) and fast (Novolog) insulin induce sex‐dependent changes in albumin (bovine serum albumin, BSA labeled with Alexa 594: C‐BSA) and total protein clearance (C‐TP) was evaluated in anesthetized adult Sprague Dawley rats of both sexes from measures of fluorescence intensity and TP in superfusate collected as it flowed off of the mesentery. Data 80–100 min post insulin (or sham) treatment were compared to that collected 0–30 min after BSAA594 injection. As before, while 0–30 min C‐TP did not differ with sex, C‐BSA was greater in males (N=4) than females (N=4) (20 vs. 30 ng/ml, p<0.05). For females by 80–110 min Novalin R reduced C‐TP (−29%) without changing C‐BSA and Novolog had no effect. In contrast, in males by 80–110 min C‐TP and C‐BSA were elevated (>2 and >4‐fold) relative to the shams. The fraction of BSA to TP differed with insulin type (3.6%, 7.7% and 4.7% for sham, Novalin R and Novalog, respectively). These sex‐differences in acute response to insulin infer that insulin resistance may also involve sex‐dependent differences in endothelial barrier function. Supported by NIH HL078816 & NASA NNJ05HF37G.
Flow/shear stress‐induced constriction of rat middle cerebral artery
Authors: Toth Peter , Vamos Zoltan , Springo Zsolt , Komoly Samuel , Doczi Tamas , Koller Akos
Published: June 2021

It is known that the intracranial volume is tightly regulated (Monroe‐Kelly doctrine). Thus we hypothesized that increases in flow/wall shear stress elicit constrictions (instead of dilations) in cerebral arteries. Changes of diameter of isolated middle cerebral arteries of rats to increases in intraluminal flow elicited by increasing pressure difference were measured. The diameter of vessels decreased significantly to increases in flow (max.: from 150±10 to 118±6 ηm, from 171±7 to 130±7ηm and from 140±10 to 116±11ηm in the presence of 60, 80, 100 mmHg pressure, respectively, which were inhibited by the non‐specific cyclooxygenase blocker indomethacin. The maximal decrease in diameter to increase in flow at 100 mmHg was 58±4 % of passive diameter obtained in Ca2+ solution. In conclusion, in contrast to responses of coronary and skeletal muscle microvessels, increases in shear stress ‐ via release of constrictor prostaglandins‐ elicit constriction in cerebral arteries, suggesting that the primary purpose of this mechanism is not to maintain wall shear stress, but to limit the increase in blood volume, thus intracranial volume/pressure. (Hungarian Nat. Sci. Res. Fund. ‐ OTKA K71591, K67984, Hungarian Neuroimaging F., NIH‐HL‐43023, AHA Founders Aff., 0555897T)
ROLE OF ENDOTHELIAL CANONICAL TRANSIENT RECEPTOR POTENTIAL (TRPC) CHANNELS IN ATP‐MEDIATED VASORELAXATION
Authors: Marrelli Sean P , Kochukov Mikhail Y , Noel Rebecca C , Mbaka Maryann M , Chen Jie
Published: June 2021

Adenosine triphosphate (ATP) is a physiological agonist that is released from multiple sources in the vascular system including red blood cells, endothelial cells, and vascular smooth muscle cells. ATP can elicit an endothelium‐dependent vasorelaxation, however, the mechanism is still unresolved. The present study examines the role of TRPC channels in the mechanism of ATP‐mediated vasorelaxation.

Experiments were performed with mouse aorta and aorta endothelial cells. Aorta contractions and relaxations were measured by artery myography. Freshly isolated endothelial cells were used for the measurement of endothelial calcium by fluorescent dye (Fura 2) and non‐selective cation currents by whole cell patch clamp.

ATP produced a concentration‐dependent (EC50 = 2 μM) relaxation in phenylephrine (3 μM) pre‐contracted arteries. In isolated endothelial cells, ATP (10 to 100 μM) stimulated a non‐selective cation current (IATP) that was inhibited by La3+ or Gd3+ (each 100 μM). ATP also produced an increase in endothelial calcium that was inhibited by La3+ (100 μM) or 2‐APB (100 μM). In summary, we present evidence that ATP stimulates vasorelaxation subsequent to endothelial cell calcium entry via TRPC‐like channels. Further studies with genetic mouse models will test the roles of specific TRPC channels in the mechanism.

Supported by NIH R01 HL088435 to SPM.
Steady state decrease of smooth muscle cell and endothelial cell pH prevents hypertension induced by angiotensin II or NO‐synthase inhibition
Authors: Aalkjær Christian , Bødtkjer Ebbe , Praetorius Jeppe
Published: June 2021

The role of steady state changes in smooth muscle and endothelial cell pH for vascular function is not known. In this study we knocked out the Na, HCO3‐cotransporter NBCn1 (slc4a7) in mice which caused a reduced pH in mesenteric artery smooth muscle and endothelial cells. Isolated arteries had reduced acetylcholine induced, NO‐mediated relaxations and rho‐kinase dependent smooth muscle Ca‐sensitivity. NBCn1 knockout mice were hypertensive, displayed attenuated blood pressure increase to NO‐synthase inhibition and blood pressure decrease to rho‐kinase inhibition and were resistant to developing hypertension during angiotensin II infusion. The increase of extracellular NO in the presence of acetylcholine was reduced in arteries from NBCn1 knockout mice while dilation to the NO‐donor S‐nitroso‐N‐acetylpenicillamine, acetylcholine‐induced endothelial Ca‐increase and endothelial NO‐synthase expression were unaffected. Rho‐kinase activity was reduced at low pH. In the absence of CO2/HCO3−, no differences were observed between isolated arteries from NBCn1 knockout and wild type mice. Using a knockout mouse to induce sustained intracellular acidification, we show a novel interaction between smooth muscle cell and endothelial cell steady state intracellular pH, vascular function and blood pressure regulation.
A novel solid state telemetry sensor for the chronic measurement of pressure in rats
Authors: Lim Matthew , Pauly Bob , McCormick Daniel , Kirton Robert , Budgett David , Kondo Masahiro , Guild Sarah‐Jane , Barrett Carolyn , Malpas Simon
Published: June 2021

Current telemetry devices for the measurement of pressure in rats utilise a catheter with a biocompatible gel and fluid which transmit the pressure waveform to a sensor. The reuse of gel/fluid based catheters is problematic with the need to regel and remove blood clots, furthermore the catheter is often damaged after repeated uses and requires refurbishment. These gel filled catheters have typically a very low frequency response; not allowing for performing meaningful dynamic analysis of cardiac pressure waveforms. These gel filled catheters also struggle with air bubbles during the regel operation which may also affect the signal integrity. We have developed a fully implantable telemeter incorporating a novel micro‐tip 2F catheter via a MEMs based sensor. The transmitter incorporates high frequency sampling of the pressure waveform and digital transmission to a remote receiver. The total implant weight is 14 gm and suitable for implantation in animals over 200 gm. Digital transmission of the signals permits co‐housing of animals without crosstalk. The ability to recharge the batteries inductively whilst monitoring provides the platform for long term and/or repeated use in animals. We report on the performance of telemeters when implanted in the aorta of Wistar rats for up to 1 month. The frequency response of the system was 500Hz allowing high fidelity measurement of arterial pressures. This high fidelity system for making direct measurements of internal pressures could provide a valuable research tool for expanding the scope of chronic studies while improving the ease of use of telemetry systems.
Altered Spatio‐Temporal Microvascular Blood Flow Distribution Patterns in Skeletal Muscle with Metabolic Syndrome
Authors: Frisbee Jefferson C. , Wu Fan , Beard Daniel A.
Published: June 2021

A characteristic of peripheral vascular disease (PVD) in the metabolic syndrome (MS) is impaired skeletal muscle perfusion:demand matching, with increased adrenergic tone being a contributing element. However, despite increases in bulk perfusion to contracting muscle following adrenoreceptor blockade, fatigue resistance remains poor unless endothelial function is restored by treatment with antioxidants. Given that antioxidant treatment alone improves neither active hyperemia nor muscle fatigue, these observations suggest that additional processes are involved beyond simple bulk perfusion. Using in situ cremaster muscle, we determined that spatial perfusion heterogeneity at bifurcations was elevated in obese Zucker rats (OZR) vs. control and this pattern was repeated at multiple successive bifurcations in the network. The increased spatial heterogeneity was not compensated for via temporal activity, as perfusion distribution at bifurcations was less labile in OZR vs. control. Intravascular tracer washout (albumin) revealed an increased heterogeneity at the network level of resolution, correctable following adrenoreceptor blockade. These observations suggest that a critical component of PVD in MS is a shift in the spatio‐temporal distribution of perfusion at bifurcations in skeletal muscle and that only interventions that improve this will have a beneficial impact on tissue performance.
Role of Arterial TRPV1 Channels in Metabolic Syndrome
Authors: Ohanyan Vahagn A. , Shamheart Patricia E. , Guarini Giacinta , Talasila Phani K. , Bratz Ian N.
Published: June 2021

We have previously shown that TRPV1 channel dependent coronary function is compromised in pigs that have metablic syndrome (MetS). However, mechanisms through which TRPV1 regulates coronary arterial function is not known. To investigate this, we employed genetically modified mice lacking TRPV1 (TRPV1−/−), Db/Db and Lean mice to determine if TRPV1 channels modulate arterial function while further investigating the hypothesis that arterial dysfunction in MetS is related to impaired TRPV1 channel contribution. Animals were subjected to in vivo infusions of either the TRPV1 agonist capsaicin or PE to examine the integrated circulatory actions of TRPV1. PE infusion (2.5 and 5 μg/kg) significantly increased mean arterial pressure (MAP) in lean and obese mice, however, PE mediated increase in MAP was blunted in TRPV1 knockout mice, suggesting a role for TRPV1 channels in PE mediated vasoconstriction. Capsaicin (1, 10, 20, 100 μg/kg) dose dependently increased blood pressure (B.P.) in lean mice (5.7 ± 1.6, 11.7 ± 2.1, 25.4 ± 3.4, 51.6 ± 3.9%, respectively) which was attenuated in Db/Db mice (3.4 ± 2.1, 3.9 ± 2.1, 7.0 ± 3.3, 17.9 ± 6.2%, respectively). TRPV1−/−mice exhibited no B.P. changes at any capsaicin concentrations. The eNOS inhibitor, L‐NAME (10mg/kg), further potentiated the increase in B.P. in both groups at 1, 10, and 20 μg/kg concentrations, with a greater increase in lean vs. Db/Db mice. Furthermore, Western analysis revealed coronary TRPV1 protein expression was reduced ~65% in Db/Db mice compared to controls. Conclusions: TRPV1 channel activation may regulate vascular tone via endothelial and smooth muscle pathways and that vascular dysfunction in Db/Db mice is related to impaired TRPV1 channel function.
The tempo of cardiovascular and metabolic responses to fasting is different between lean and obese mice
Authors: Tanner Jason , Kearns Devin , Kim Bum Jun , Sloan Crystal , Yang Guangrui , Jia Zhanjun , Yang Tianxin , Abel E. Dale , Symons J. David
Published: June 2021

Laboratory animals commonly are fasted prior to experimentation. Fasting evokes reductions in heart rate (HR), blood pressure (BP), heat production, and oxygen consumption (VO2) in rodents. We hypothesized that cardiovascular and metabolic responses to a 16‐hour (h) fast (16:00 to 08:00) at 22ºC are blunted in obese vs. lean male C57BL/6J mice. Mice that consumed 45% fat (HF) chow for 98±5 days had elevated (p<0.05) body fat (DEXA), serum leptin (ELISA), HR and BP (72 h biotelemetry), and heat production (72 h metabolic chamber), and lower (p<0.05) VO2 (72 h metabolic chamber) vs. animals that consumed 10% fat (CON) chow (n=16 per group). As anticipated, each variable decreased (p<0.05) during the fasting segment. However, fasting‐induced reductions in cardiovascular and metabolic variables occurred approximately 4 h and 7 h sooner (p<0.05), respectively, in HF vs. CON mice. Despite differences in the tempo of each response between groups, reductions from the fed condition were identical among animals after 16 h of fasting. Thus, 16 h is a suitable fasting duration for studies of cardiovascular complications in murine models of diet‐induced obesity but shorter periods could be confounded by differential rates of metabolic and vascular adaptations in this species. NIHR15HL091493, ADA7‐08‐RA‐164
Ceramide‐induced disruption of endothelial nitric oxide synthase dimerization in bovine aortic endothelial cells (BAECs) is not secondary to peroxynitrite formation
Authors: Wilson Lloyd , Zhang Quanjiang , Arrant Colton , Pettey Dix , Kowalski Chris , McCamey Dane , Boehme Christoph , Baker William , Soorappan Rajasekaran N , Abel E Dale , Symons J David
Published: June 2021

We have used pharmacological and genetic approaches in mice, arteries, and/or BAECs to show that ceramide impairs arterial function by decreasing eNOS activity in a tissue autonomous manner. eNOS dimerization is required for optimal eNOS enzymatic activity. Peroxynitrite uncouples eNOS by disrupting protein dimer formation.We hypothesized that ceramide‐induced superoxide anion (O2•−) generation disrupts eNOS dimer formation as a result of increased peroxynitrite accumulation. BAECs were treated for 3 h with: vehicle (V); 500 μM palmitate (P); or P + the ceramide synthesis inhibitor myriocin (M, 10 μM). Relative to V, P increased: ceramide accumulation (HPLC) by 1.6±0.1‐fold (n=6); reactive oxygen species (ROS) generation (DCFDA fluorescence) by 3.2±0.2‐fold (n=31); and O2• − production (ESR) by 1.27±0.08‐fold (n=11, all p<0.05). These changes were blunted (p<0.05) in BAECs treated with P + M. Three estimates of nitrotyrosine formation [i.e., immunoblotting (n=14–18), ELISA (n=16), and immunostaining (n=12)] showed no evidence for P‐evoked peroxynitrite accumulation. Despite the lack of P‐evoked peroxynitrite formation, insulin (n=10) and VEGF (n=10)‐mediated increases (p<0.05) in p‐eNOS at S1177 and S617, and the eNOS monomer : dimer ratio were prevented (p<0.05) by P, but were restored by co‐incubation of P + M. These findings indicate that ceramide‐evoked disruption of agonist‐mediated eNOS phosphorylation and dimerization occurs via a peroxynitrite – independent mechanism. NIHR15HL091493, ADA7‐08‐RA‐164
O‐GlcNAc signaling regulates cardiac hypertrophy via NFAT activation
Authors: di Tarso Fernandes Facundo Heberty , Eli Brainard Robert , Jones Steven Paul
Published: June 2021

Calcineurin regulates the dephosphorylation and nuclear translocation of the cardiac hypertophy transcription factor, Nuclear Factor of Activated T‐cells (NFAT). O‐linked beta‐N‐acetyl glucosamine (O‐GlcNAc) has emerged as a highly dynamic post‐translational modification of serine and threonine residues regulating physiological and stress processes. Here, we show that hypertrophy (via phenylephrine, 100 μM – 6 hours) augmented O‐GlcNAc signaling and, through the use of an NFAT‐luciferase reporter, was associated with NFAT activation in Neonatal Rat Cardiac Myocytes. Adenoviral O‐GlcNAcase overexpression or hexosamine pathway inhibition (i.e. reduction in O‐GlcNAc signaling) reversed hypertrophy‐induced NFAT activation similar to the prototypic calcineurin inhibitor, cyclosporin A. Interestingly, the O‐glycosylating enzyme O‐GlcNAc Transferase augmented O‐GlcNAc levels and activated NFAT, even in the absence of hypertrophic stimulation. Hearts from mice subjected to pressure overload induced hypertrophy (i.e. Transverse Aortic Constriction) exhibited augmented O‐GlcNAc levels and elevated ANP and BNP expression. Taken together, these results demonstrate a critical role of O‐GlcNAc signaling in NFAT activation during hypertrophy and provide evidence that O‐GlcNAc is coordinated with the onset and progression of cardiac hypertrophy. This represents a potentially significant and novel mechanism of cardiac hypertrophy, which may be of particular interest in studies of diabetic cardiomyopathy.

Financial support: NIH, American Heart Association
Diosgenin suppress cardiac apoptosis and enhance survival pathway in ovariectomized rats
Authors: Lee Shin‐Da , Tasi Ching‐Yi , Ou Hsiu‐Chung , Huang Chih‐Yang
Published: June 2021

Objective

The study was to evaluate the effects of diosgenin on cardiac apoptotic and survival pathways in bilateral ovariectomied animal model.

Methods

Sixty female Wistar rats at 6–7 months of age were divided into sham‐operated group (Sham), bilateral ovariectomized group (OVX) for 2 months, and OVX groups with 10 mg/kg and 50 mg/kg diosgenin daily (Ovx 10, Ovx 50) in the 2nd month. The excised hearts were measured by heart weight index, hematoxylin‐eosin staining, positive TUNEL assays, and Western blotting.

Results

Diosgenin decreased OVX‐induced cardiac TUNEL‐positive apoptotic cells. Diosgenin decreased OVX‐induced Fas ligand, Fas death receptors, Fas‐associated death domain (FADD), activated caspase 8, and activated caspase 3 (Fas pathways). Diosgenin decreased OVX‐induced Bax, Bad, Bax‐to‐Bcl2 ratio, activated caspase 9, and activated caspase 3 (mitochondria pathway). Diosgenin increased ER‐beta, IGF1,IGF1R, PI3K, and Akt(survival pathway).

Conclusions

Diosgenin suppressed ovariectomy‐induced cardiac Fas‐dependent and mitochondria‐dependent apoptotic pathways and enhance IGF‐1 related survival pathway. The findings may provide one of possible therapeutic approaches of diosgenin for potentially preventing cardiac apoptosis after bilateral ovariectomy or post‐menopause.
Postnatal maturation and hypoxic acclimatization modulate PKG‐mediated activation of BK channels in ovine cerebral arteries
Authors: Williams James M , Stockman Sara L. , Lincoln Thomas M. , Pearce William J.
Published: June 2021

NO‐dependent relaxation of ovine cerebral arteries is enhanced during postnatal maturation but is attenuated by acclimatization to high altitude. Because NO‐mediated vasorelaxation is mediated by activation of PKG, which in turn activates large conductance BK channels, we hypothesized that the effects of both maturation and chronic hypoxia on NO‐dependent relaxation are mediated by modulation of PKG effects on BK channels. In middle cerebral arteries from normoxic and chronically hypoxic fetal and adult sheep, iberiotoxin (IBTX, an inhibitor of BK channels) enhanced the maximum contractile response to 5HT ≈10% in both age groups, but 8pCPT‐cGMP (8pCPT, a PKG activator) decreased this response ≈15% in fetal and ≈20% in adult arteries. Addition of 8pCPT followed by IBTX produced responses similar to controls in both age groups. In arteries treated with cumulative log dose increases of IBTX before or after incubation with 8pCPT, IBTX significantly enhanced basal tone ≈40% in both age groups. Preincubation with 8pCPT attenuated the contractile responses to IBTX by ≈70% in fetal and ≈90% in adult arteries. Addition of 8pCPT following maximum responses to IBTX decreased tone ≈30% in fetal and ≈40% in adult arteries. These results indicate that PKG enhances BK channel activity more in adult than fetal arteries, and markedly less in hypoxic than normoxic arteries.

Supported by USPHS Grants HL54120, HD31266, & HL64867.
PPARα agonists acutely dilate the mouse middle cerebral artery
Authors: Parelkar Nikhil K , Badr Mostafa Z , Andresen Jon
Published: June 2021

Peroxisome proliferator activated receptors (PPARs) are nuclear hormone receptors that are mainly involved in lipid metabolism. Studies investigating the role of PPARs have mainly focused on cardioprotective and lipid lowering effects of PPAR agonists. The purpose of this study was to investigate possible acute effects of the PPARα agonists gemfibrozil, WY14643, and GW7647 in pressurized and perfused mouse middle cerebral arteries (MCAs). MCAs were mounted between two glass capillary pipettes in a myograph containing Krebs buffer heated to 37°C. Arteries were pressurized to 75 mm Hg and perfused with Krebs. In MCAs preconstricted with phenylephrine (10−5 M), gemfibrozil was a weak dilator achieving a peak dilation of only 27.8%. The more selective PPARα agonists WY14643 and GW7647, however, maximally dilated preconstricted MCAs in a concentration‐dependant manner. The highly PPARα specific compound GW7647 was 50‐fold more potent than WY14643. GW7647 had logEC50=‐5.86±0.14 whereas, WY14643 had logEC50=−4.02±0.06. Neither endothelial denudation nor nitric oxide synthase and cycloxygenase inhibition altered the dilation to GW7647. This study demonstrates that PPARα agonists acutely dilate cerebral arteries in vitro and suggests a higher vasodilatory capacity with greater PPARα selectivity. This research was supported by an AHA SDG (0735053N) and UMKC start‐up funds.
Indication for cholinergically mediated cerebral vasodilatation during static exercise in humans
Authors: Seifert Thomas , Fisher James P , Young Colin N , Hartwich Doreen , Fadel Paul J , Secher Niels H
Published: June 2021

Cholinergically mediated vasodilatation is reported in humans, but its importance for cerebral perfusion during exercise is unknown. The increase in middle cerebral artery blood flow velocity (MCA Vmean) during static handgrip exercise was evaluated by blockade of acetylcholine receptors as well as with beta‐adrenergic blockade, in nine males in separate, randomized and counterbalanced trials over two minutes. Mean arterial pressure (MAP) increased during both 25 % and 40 % maximal voluntary contraction (MVC) handgrip (P < 0.01) with no effect of treatment. Resting cardiac output was reduced by ~20% with beta‐adrenergic blockade (P < 0.05) and increased by ~40% with vagal‐blockade (P < 0.05). Compared to control, exercise‐induced increases in cardiac output were attenuated with beta‐adrenergic blockade (P < 0.01) and abolished with cholinergic blockade. MCA Vmean increased ~16% during control exercise (independent of intensity; P < 0.01). During 25% MVC handgrip, both cholinergic and beta‐adrenergic blockade abolished the exercise‐induced increase in MCA Vmean (~3 % and ~7 %, respectively), whereas at 40 % MVC only cholinergic blockade abolished the increase. These findings suggest that the increase in cerebral perfusion during exercise is dependent upon cardiac output, but that a cholinergically mediated vasodilatatory mechanism may also be important.
Genomics approach using calcineurin/NFAT inhibitors to identify novel effectors of vascular smooth muscle phenotypic modulation
Authors: Lee Monica Y , Garvey Sean M , Wamhoff Brian R
Published: June 2021

Calcineurin (Cn) and the NFAT family of transcription factors are critical in vascular smooth muscle cell (SMC) development and pathology. We used a genomics approach to identify novel transcriptional targets of NFAT in SMC phenotypic modulation. SMC phenotypic modulation was induced by treatment with platelet‐derived growth factor‐BB (PDGF). PDGF‐induced proliferation was blocked by either the Cn inhibitor, cyclosporin A (CsA), or the NFAT inhibitor, A285222. Genome‐wide expression arrays were used to identify genes in rat aortic SMCs both 1) differentially expressed in response to PDGF at 3 hours and 2) whose differential expression was reduced by both CsA and A285222; genes theoretically positively regulated by Cn/NFAT. The top 20 PDGF‐upregulated probe sets sensitive to both drugs corresponded to 17 genes. 15 of these genes were expressed at higher levels in intact rat arteries compared to visceral smooth muscle tissues. For validation, SMCs were treated at 10 time‐points across 24 hours. Real‐time RTPCR showed that CsA and A285222 reduced the early upregulation of DSCR1 (Cn regulator), DUSP1 (MAPK inactivator), and PROCR (protein C receptor) more than 50% compared to vehicle controls. Intriguingly, the PROCR promoter contains a highly conserved NFAT site at the ‐8 position. We report PROCR and DUSP1 as novel NFAT‐dependent early genes in VSMC phenotypic modulation. AHA predoc APS postdoc NIH HL81682 AHA SDG
Correlativity between the plasma homocysteine and endogenous carbon monoxide of penile corpus cavernosum in type 2 diabetes
Authors: Qin Wen‐Bo , Xu Hong‐Wei , Kang Yu‐Ming , Chi Bao‐Jin , Wei Xiao‐Dong , Wang Shu‐Qing , Liu Jun‐Xing
Published: June 2021

The present study explored whether homocysteine (Hcy) is an independent effect factor for endogenous carbon monoxide (CO) of rat penile corpus cavernosum of type 2 diabetic erectile dysfunction of adult male Wister rats. Ten rats were selected randomly from fifty of three‐months‐old male Wistar rats supplied by normal feeding, as control group (A group). Other forty rats were fed with high‐fat and high glucose food. After four weeks they were injected with streptozotocin (30mg/kg). Filtered thirty diabetes mellitus divided into three groups: diabetic rat (B group), diabetic rat with insulin treatment (C group), diabetic rat therapy in folic acid and vitamin B12 groups (D group). A group supplied by normal feeding, B, C, D groups were fed with high‐fat and high glucose. Results showed that the level of plasma total Hcy of B group was obviously increased compared with the controls, the erection rate of the penile cavernous tissue and the activity of CO in penile corpus cavernosum decreased significantly. The level of plasma total Hcy of C and D group was obviously decreased, while the activity of CO and the erection rate were higher than B group. The high level of plasma total Hcy of type 2 diabetes maybe a molecular mechanism that induce the decline of the activity of CO of penile corpus cavernous, and then cause diabetic erectile dysfunction(DMED).
Cardiac sympathetic activity assessed by heart rate variability indicates myocardial ischemia on cold exposure in diabetes
Authors: Sasaki Keita , Matsushita Shonosuke , Sakakibara Yuzuru
Published: June 2021

Purpose

Cold exposure is one of the major risk factors for cardiac events in diabetes. The aim of this study is how cardiac sympathetic nerve activity (SNA) is affected by temporal cold exposure in diabetes using heart rate variability (HRV).

Methods

Male Wistar Rat (n=12) were divided into two groups: Control and Diabetes. Diabetes was induced by streptozocin. Lower extremity was sprayed for cold vapor for 5 seconds. Rectal and subcutaneous tissue temperature, flow velocity of lower extremity using laser Doppler flow meter, frequency domain analysis of HRV and ST change were measured up to 15 min from initial cold exposure.

Results

SNA was able to define as a power between 0 and 0.2 Hz in HRV by use of propranolol (60mg/kg). SNA was enhanced in diabetes than control (p<0.05) associated with reduction of blood flow (p<0.05). SNA was decreased by cold exposure in control (p<0.005), however, diabetes did not show significant reduction. SNA was enhanced significantly in diabetes at 1, 5, 10 and 15 min after cold exposure compared with control (p<0.01, p<0.005, p<0.05, p<0.0005, p<0.01, respectively). ST change was significantly larger in diabetes than control in 1 and 5 min after cold exposure (p<0.001, p<0.005).

Conclusion

Cardiac SNA was decreased after cold exposure to lower extremity in control. In contrast, cardiac SNA was enhanced in diabetes than control, which may lead to cardiac ischemia in cold exposure in diabetes.
Aldose reductase deficiency enhances high fat diet‐induced hyper‐insulinemia and endothelial dysfunction
Authors: Mehta Ishan , Conklin Daniel , Srivastava Sanjay , Bhatnagar Aruni
Published: June 2021

Obesity and Type II diabetes enhance cardiovascular disease risk 2–9 times and are reaching epidemic levels in the U.S. with ~16 million diabetics and >30 million obese people. Because endothelial dysfunction is associated with high fat intake and increased cardiovascular disease risk, we studied the relationship between high fat diet (HFD), endothelial dysfunction and aldose reductase (AR), a glucose‐ and aldehyde‐metabolizing enzyme. Thus, we fed young male C57BL/6 and AR‐null mice a normal chow (NC; 21% kcal fat) or HFD (42% kcal fat) for 12 weeks. HFD significantly increased glucose intolerance, plasma cholesterol, and plasma insulin in both C57BL/6 and AR‐null mice compared with NC‐fed mice, but HFD induced a greater hyperinsulinemia in AR‐null compared with HFD‐fed C57BL/6 mice. Similarly, HFD significantly decreased aortic endothelial‐dependent relaxation only in AR‐null mice. Also HFD depressed plasma NOx to a greater degree in AR‐null mice. Collectively, these data indicate that AR deficiency specifically enhances HFD‐induced endothelial dysfunction by decreasing NO production and/or bioavailability. We conclude that AR deficiency enhances the sensitivity of the endothelium to oxidative stress induced by HFD perhaps via loss of AR‐mediated detoxification of lipid peroxidation‐derived aldehydes. This study supported by UofL Diabetes and Obesity Center P20RR024489 and NIEHS T35 ES014559.
Functional and molecular characterization of vascular TREK‐1 channel and its role in EDHF‐mediated vasodilation and hypertension
Authors: Kaistha Brajesh Pratap , Busch Christoph , Kaistha Anuradha , Kacik Michael , Köhler Ralf , Hoyer Joachim
Published: June 2021

Potassium channels are crucial effector proteins in endothelial function. Here we investigated functions of the TREK‐1 in vascular endothelium and analysed its expression during hypertension. Functional and molecular expression of endothelial TREK‐1 was analyzed by patch‐clamp, RT‐PCR and pressure‐myography. K+ outward currents displaying the characteristics of TREK‐1 were observed following various TREK‐1‐activating stimuli like isoflurane, riluzole, membrane stretch, intracellular acidosis and polyunsaturated fatty acids. Increased endothelial TREK‐1 current amplitudes were detected in KCa3.1−/− mice exhibiting elevated blood pressure compared to controls. Increased TREK‐1 expression was also seen in SHR‐rats. Pressure myography revealed that TREK‐1 mediated EDHF‐type dilator responses to isoflurane, arachidonic acid and a‐linolenic acid in murine carotid artery. Responses to a‐linolenic acid and isoflurane increased about twofold in KCa3.1−/− mice compared to controls and an inverse correlation was seen between magnitude of vasodilatory responses to isoflurane and systolic blood pressure in KCa3.1−/− mice. We successfully exhibited a relation between TREK‐1 expression in vascular endothelium and hypertension and concluded that TREK‐1 may play a protective role in the cardiovascular system during hypertension by providing a novel endothelium‐mediated vasodilator response.
Arterial Compliance in Untreated Hypertensive Elderly: Implications for Gender Differences
Authors: Galbreath Melyn , Shibata Shigeki , VanGundy Tiffany B. , Meier Rhonda L. , Jarvis Sara S. , Vongpatanasin Wanpen , Levine Benjamin D. , Fu Qi
Published: June 2021

We tested the hypothesis that elderly hypertensive women have increased arterial stiffness and altered vascular responses compared to elderly men. 15 untreated elderly hypertensive men, 5 hypertensive and 4 normotensive women, were studied. Supine hemodynamics, including arm BP, heart rate (HR), cardiac output (Qc), stroke volume (SV=Qc/HR), and total peripheral resistance (TPR=meanBP/Qc) were measured. Augmentation index (Aix), and pulse wave velocity (PWV) were assessed. Effective arterial elastance (Ea=central systolic BP/SV) and systemic arterial compliance (SAC=SV/pulse pressure) were calculated. Aix was similar across female and male hypertensives (24±6 vs 25±3%), with significance noted between hypertensive males and normotensive females (14 ± 9%, P<0.05). Central PWV was not different across groups. Peripheral PWV tended to be higher in female hypertensives than normotensives (1018±149 vs 850±70 m/s, P=0.08). Hypertensive and normotensive females had a higher Ea (2.39±0.56, 2.34±0.45 vs 1.59±0.33 mmHg/mL, P<0.05), decreased SAC (P<0.05), and elevated TPR versus hypertensive men (P<0.05). These preliminary data support gender specific differences in cardiac function and vascular response in elderly hypertensives. It is suggested that ventricular‐arterial function, a non‐neural mechanism, may be one potential explanation for sex differences in hypertensive elderly.
Salt sensitive hypertension associated with stem cell defect in the renal medulla of Dahl S rats
Authors: Wang Zhengchao , Xia Min , Zhu Qing , Li Pin‐Lan , Li Ningjun
Published: June 2021

Given the importance of the renal medulla in the regulation of sodium excretion and salt sensitivity of arterial pressure, stem cells in the renal medullary niche may contribute to the maintenance of normal cell homeostasis and functional integrity in this kidney region and thereby to the long‐term regulation of arterial pressure. The present study tested the hypothesis that stem cell defect in the renal medulla is involved in salt‐sensitive hypertension in Dahl S (DS) rats due to enhanced local inflammatory response. By immunostaining and flowcytometric analysis, it was found that stem cell marker CD133‐positive cells significantly decreased by 50% in the renal medulla from DS rats vs. control rats. However, pro‐inflammatory cytokine interleukin‐1alpha significantly increased by two folds in response to high salt intake in DS rats vs. control rats. Renal medullary infusion of valproic acid, a stem cell activator, in DS rats for 2 weeks reversed high salt‐induced increase in interluekin‐1alpha and attenuated high salt‐induced increase of arterial pressure (108.1±3.5 mmHg on low salt diet, 148.4±0.2 mmHg on high salt diet and 129±2.8 mmHg on high salt plus valproic acid). It is suggested that stem cell defect may contribute to the renal medullary dysfunction and development of hypertension in DS rats. The protective role of stem cells is associated with their anti‐inflammatory action (support: NIH grant HL‐89563).