bluuebunny/crossref_metadata_2025 huggingface dataset:
Ponto‐medullary transection attenuates sympathorespiratory coupling and eliminates cardiac sinus arrhythmia in the in situ rat
Authors: Baekey David M , Dick Thomas E , Paton Julian FR
Published: June 2021

Sympathetic nerve activity obtained from experimental animals demonstrates a pronounced modulation with the central respiratory rhythm. This modulation is mirrored in heart rate (respiratory sinus arrhythmia) and arterial pressure (Hering‐Traube waves) that are common to all mammals. The neural substrate responsible for sympatho‐respiratory coupling has not yet been defined. Based on recent evidence, we hypothesized that pontine neuron populations may be key components for this synchrony. Using the arterially perfused in situ preparation of rat, we recorded neural activities from the left phrenic nerve, central end of the vagus nerve and thoracic sympathetic chain (T8‐T10), as well as heart rate. Following a control period, the brainstem was transected transversely at the rostral edge of the facial nucleus, separating the pons and medulla. Respiration remained rhythmic but apneustic, with an increase of inspiratory duration. Both post‐inspiratory activity in the vagus nerve and the cardiac sinus arrhythmia were abolished while the synchronization of sympathetic outflow with the central respiratory signal was reduced substantially both in amplitude and duration. We surmise that descending drives from the pons are critical for the normal coupling of respiratory related modulations of sympathetic outflows destined for the heart and vasculature. Funded by the Leverhulme Trust (University of Bristol).
Kinins do not alter cardiovascular and sympathetic responses to isometric exercise in humans
Authors: Kuipers Nathan T , Sauder Charity L , Kearney Matthew L , Ray Chester A
Published: June 2021

Bradykinin activates muscle afferents responsible for mediating the exercise pressor reflex in animals. This study was designed to test if cardiovascular and muscle sympathetic nerve activity (MSNA) responses to exercise are affected by kinins in humans. This study was conducted in a double‐blinded, placebo controlled, randomized manner. During drug treatment eight male (25±2 yr) subjects were given 20 mg of the ACE‐inhibitor quinapril to increase plasma kinins. Measurements included mean arterial blood pressure (MAP), heart rate, renal blood flow velocity (Doppler ultrasound), calf blood flow (plethysmography) and MSNA (microneurography). ACE‐inhibitor treatment lowered MAP (−9±3 mmHg) at baseline but did not alter heart rate, arterial blood pressure, renal and calf vascular conductance, and MSNA responses to ischemic isometric handgrip performed to fatigue. Cardiovascular and MSNA responses to postexercise muscle ischemia did not differ between treatments. This finding indicates that acute increases in kinins do not alter the exercise pressor reflex in humans.

Research supported by NIH DC006459, HL077670, & MO1RR10732
Is it inflation or central inspiration that attenuates baroreflex sensitivity (BRS) in Man?.
Authors: Parkes Michael J. , Hollow Michael R. , Clutton‐Brock Thomas H
Published: June 2021

Breathing reduces the heart period component of BRS. Is the cause predominantly pulmonary inflation or central inspiration? Hypocapnia (HA) augments the pulmonary stretch reflex but reduces the central respiratory rhythm. If HA further reduces BRS, the predominant cause of this respiratory attenuation is inflation, whereas if HA increases BRS the predominant cause is central inspiration.

BRS was measured by spontaneous sequence analysis in 7 healthy subjects in eupnea (PetCO2 38 ± 1 mmHg) and during mechanical hyperventilation by facemask, where subjects breathed with the ventilator, in either normocapnia or HA.

In eupnea BRS was attenuated in inflation/inspiration vs. deflation/expiration (11 ±3 ms/mmHg vs. 24 ±7 ms/mmHg, P<0.005). Averaged mean blood pressure was 90 ±3 mmHg and mean heart period was 0.88 ± 0.06 s. Mechanical hyperventilation (PetCO2 = 39 ±1 mmHg) had no signficant effects vs. eupnea on blood pressure, heart period or BRS.

HA (PetCO2 = 23±0 mmHg) had no significant effect on blood pressure or heart period but reduced mean BRS in inflation/inspiration to 6±1 ms/mmHg (n=6, P< 0.001). This effect also carried over to reduce BRS (7 ± 2 ms/mmHg, n=7, P<0.05) in deflation/expiration.

Because HA further reduces (rather than increases) BRS, we conclude that under these conditions the cause of the respiratory attenuation of BRS is predominantly inflation rather than central inspiration.
Neurovascular Transduction in Humans: New Insights from Multifiber Muscle Sympathetic Recordings
Authors: Taylor J. Andrew , Tan Can Ozan , Tamisier Renaud
Published: June 2021

Few studies have explored neurovascular transduction with sufficient time resolution to derive characteristic delays or without deriving indices of vasomotor responses (i.e., resistance or conductance) that may generate misleading nonlinearities. Our recently developed method to identify individual nerve firings was used to determine features of sympathetic activity that underlie neurovascular transduction. Sympathetic recordings, beat‐by‐beat arterial pressures, and popliteal blood flows were obtained in 11 volunteers during 15 min of rest (low tonic sympathetic activity), isometric handgrip to fatigue (increasing sympathetic activity), and 3 min of post‐handgrip ischemia (high tonic sympathetic activity). Each phase was analyzed separately to obtain lags between sympathetic firing and its cumulative effect on blood flow. Pressure was treated as a parameter directly relating to flow within a single beat. The delay between sympathetic firing and blood flow was approximately 5 sec at rest (5.1+/−1.7), was slightly increased with exercise (6.4+/−1.3), but was doubled during post‐exercise ischemia (10.2+/−1.6). Neurovascular transduction was slightly lower at rest than during exercise (−0.12+/−0.04 vs −0.14+/−0.06), but was markedly less during post‐exercise ischemia (−0.06+/−0.04). Thus, neurovascular transduction may not just differ across individuals, but also across conditions.
Gene transfer of Cu‐Zn superoxide dismutase to the carotid body reverses enhanced chemoreceptor function in heart failure rabbits
Authors: Ding Yanfeng , Li Yu‐Long , Davisson Robin L , Schulz Harold D
Published: June 2021

Peripheral chemoreflex sensitivity is potentiated in both clinical and experimental chronic heart failure (CHF). NADPH oxidase‐derived superoxide anion mediates angiotensin II‐enhanced carotid body (CB) chemoreceptor sensitivity in CHF rabbits, and tempol, the superoxide dismutase (SOD) mimetic, inhibits this Ang II‐ and CHF‐enhanced superoxide anion effect (Cardiovasc Res. 2007, 75:546–54). Here we investigated the effect of adenoviral Cu‐Zn SOD gene transfer in the CB on chemoreceptor activity and function in CHF rabbits. Ad Cu‐Zn SOD (1×108 pfu/ml) gene transfer to the CBs significantly reduced the baseline renal sympathetic nerve activity (RSNA) and the response of RSNA to hypoxia in the CHF rabbits. Baseline single‐fiber discharge from CB chemoreceptors during normoxia and the response to hypoxia were enhanced in CHF vs. sham rabbits. Ad Cu‐Zn SOD decreased the baseline discharge (2.9 ± 1.1 vs. 8.1 ± 0.8 imp/s at 104 ± 2.4 mm Hg PO2) and the response to hypoxia (16.4 ± 2.3 vs. 38.7 ± 2.3 imp/s at 41 ± 2.6 mm Hg PO2, p<0.05) in CHF rabbits. In addition, Ad Cu‐Zn SOD normalized the blunted IK in CB glomus cells from CHF rabbits (1020 ± 142 vs. 2156 ± 230 pA at +70 mV, p<0.05). Ad SOD did not affect CB afferent discharge and IK of CB glomus cells in sham rabbits. These results suggest that Cu‐Zn SOD activity in the CB may be involved in the enhanced activity of the CB chemoreceptors and peripheral chemoreflex function in CHF rabbits.
Nuclear factor κB‐associated inflammation mediates impaired vascular endothelial function in non‐diabetic middle‐aged and older overweight/obese men
Authors: Pierce Gary L. , Lesniewski Lisa A. , Lawson Brooke , Beske Stacy D. , Seals Douglas R.
Published: June 2021

Healthy middle‐aged/older (MA/O) sedentary men demonstrate vascular endothelial dysfunction with increased endothelial expression of nuclear factor‐kappa B (NFκB), a key proinflammatory nuclear transcription factor. However, there is no direct evidence that NFκB‐associated vascular inflammation mediates endothelial dysfunction in MA/O adults. High doses of Salsalate (4500 mg/d; therapeutic [plasma] 22.2 ± 1.7 mg/100ml, mean ± SE), an aspirin‐like agent that inhibits NFκB, was ingested for 4 days (randomized, placebo‐controlled, double‐blind crossover design) by 10 non‐diabetic overweight or obese MA/O men (62 ± 2 y; BMI 31.4 ± 2 kg/m2) with low‐grade inflammation (plasma C‐reactive protein 2.0 ± 0.7 mg/L). Salsalate reduced total (−30%: 0.42 ± 0.07 vs. 0.60 ± 0.09 intensity/HUVEC intensity, P=0.03) and nuclear (−23%: 128 ± 25 vs. 167 ± 24 total intensity, P=0.06) expression of NFκB p65 in vascular endothelial cells (quantitative immunofluorescence), and increased endothelium‐dependent dilation (EDD, brachial artery flow‐mediated dilation) by 100% (6.2 ± 0.6 vs. 3.1 ± 0.6%, P<0.001) without affecting endothelium‐independent dilation (brachial artery dilation to sublingual nitroglycerin) (19.5 ± 2.2 vs. 19.3 ± 1.6%, P=0.80). These results support the idea that NFκB‐associated vascular inflammation mediates endothelial dysfunction in MA/O overweight/obese men. NIH AG006537, AG013038, AG022241
Vascular insulin resistance in cerebral arteries of Zucker obese rats is mediated by uncoupled eNOS and NADPH oxidase
Authors: Katakam Prasad V.G. , Snipes James A. , Busija David W.
Published: June 2021

Insulin resistance (IR) is a risk factor for cerebrovascular disease. We evaluated the responses to insulin in isolated cerebral arteries from Zucker obese rats (ZO) with IR and lean rats (ZL). Insulin responses were determined in the presence and absence of endothelium, inhibitors of calcium‐activated K+ channels (KCa), NOS and NADPH oxidase (iberiotoxin, L‐NAME and apocynin, respectively). Insulin induced only vasodilation in ZL while a biphasic response with an initial constriction followed by a diminished dilation was observed in ZO (‰ maximal relaxation: 52±10 in ZL vs. 13±8 in ZO, p<0.05). Iberiotoxin abolished vasodilation to insulin in both groups. In ZL, L‐NAME promoted vasoconstriction to insulin while apocynin had no effect. In ZO, insulin induced vasoconstriction was reduced by L‐NAME and apocynin. Endothelial denudation diminished vasodilation to insulin in ZL while ZO were unaffected, suggesting an endothelium independent vasodilation in ZL. Thus, insulin induced vasodilation in cerebral arteries was mediated by endothelium, NO and KCa channels. Insulin caused abnormal vasoconstriction and diminished vasodilation in ZO that may be due to oxidative stress from uncoupled eNOS and NADPH oxidase. Support: NIH grants HL‐030260, HL‐065380, HL‐077731.
Do different Ca entry mechanisms mediate Endothelin‐1‐induced contraction of rat aorta and vena cava?
Authors: Tykocki Nathan Roger , Jackson William F. , Watts Stephanie W.
Published: June 2021

Endothelin‐1 (ET‐1) is a potent vasoconstrictor for venous and arterial vasculature. ET‐1 mediated contraction in rat thoracic aorta (RA) is Ca‐dependent, involving non‐selective cation channels (NSCC) and store‐operated Ca channels (SOCC) as sources of Ca influx. However, the Ca‐dependent contractile mechanisms of rat vena cava (RVC) to ET‐1 are unknown. We hypothesize that contraction to ET‐1 is dependent on Ca‐channel function, and that RA and RVC utilize different Ca channels due to differing function, physiology, and ET receptor expression. Of five antagonists tested, only the SOCC antagonist LOE‐908 (10 mM) significantly inhibited ET‐1‐induced contraction of RVC (logEC50[M]: −8.39±0.08 vs. −8.21±0.04). Zero Ca PSS/1mM EGTA abolished ET‐1 responses in RA, but only attenuated the response in RVC (125% ± 35% of NE response vs. 639% ± 50%). Thus, a component of RVC contraction to ET‐1 involves SOCC channels. RVC responded to ET‐1 even without [Ca]o, suggesting either large intracellular stores of Ca, or a Ca‐independent contractile pathway. This implies ET‐1–induced contraction of RA and RVC involve different Cainflux pathways, and different signaling mechanisms. We speculate that these differences may be attributed to differing interactions of ETA and ETB receptors in RVC compared to RA. Supported by NIH HL070687 to SWW and HL32469 to WFJ.
A novel effect of P2X7 receptor antagonist ‐ oxidized ATP in mouse aorta
Authors: Chiao Chin‐Wei , Tostes Rita C. A. , Webb R. Clinton
Published: June 2021

Introduction: The P2X7 receptor is an unusual non‐desensitizing, cation selective, ion channel directly gated by extracellular ATP or ATP analogs. It is involved in several processes relevant to inflammation and immunity. Oxidized ATP (oATP) is a potent irreversible antagonist of P2X7 receptor, and it is not influenced by the presence of extracellular Na+ or K+. In our previous vascular functional study, we found that high concentration of oATP inhibits contractile response to PE.

Hypothesis: oATP induces a factor to abolish the contractile response of PE in mouse aortic rings.

Methods & Results: Vascular reactivity was evaluated using standard methods in aortic rings, with endothelium, from male C57Bl/6 mice. Incubation with oATP (24 h) inhibited 10−6M PE‐induced contractions in a concentration‐dependent way: oATP 50 μM (80.37±3.37 %, normalized to 120 mM KCl), 100 μM (47.11±1.54 %), 150 μM (46.43±4.64 %), and 250 μM (32.77±4.37 %). L‐NAME or 1400W reversed the abolished PE contractile response in 250 μM oATP. However, indomethacin did not. oATP did not alter eNOS, iNOS, or nNOS protein expression, but decreased COX2 protein expression.

Conclusion: oATP abolished PE‐induced contractile response in mouse aortic rings. This effect might be induced by activation of the nitric oxide signaling pathway.
Gender differences in heat‐induced attenuation of vasoconstriction
Authors: Eisenhauer Jessica A , Kluess Heidi A , Anton Maria M , DeLorey Darren S , Buckwalter John B , Clifford Philip S
Published: June 2021

The purpose of the study was to determine if heat attenuates sympathetic vasoconstriction in females as it does in male rats (Kluess et al., 2005). Since females have higher α1‐adrenergic tone than males, the hypothesis was that the magnitude of heat attenuation would be less in females. The femoral arteries from 15 female (279±11g) and 16 male (290±10g) Sprague‐Dawley rats were prepared for wire myography. Field stimulation (2–60Hz for 144 impulses) and dose response curves for the P2X agonist, αβ‐methylene ATP (mATP: 10−7 to 10−3M) and the α1‐agonist, phenylephrine (PE: 10−7 to 10−4M) were performed at bath temperatures of 37°C and 41°C. Heat attenuated tension produced during field stimulation in both genders, but there was greater attenuation in males (−65±13% on average) compared to females (−48±10% on average; p<0.05). Heat reduced the tension produced by mATP in female and male femoral arteries, but the slope was higher in males at 41°C (1.39±0.17g/log M mATP), than females at 41°C (0.83±0.09 g/log M mATP; p=0.01). The responsiveness to phenylephrine was unaffected by heat. Skeletal muscle arteries in female rats experience modest heat attenuation, but the magnitude of change is less than for age and weight matched males. The primary mechanism for heat‐induced attenuation of vasoconstriction in the femoral artery in males and females is P2X purinergic receptors.
Bcl‐2 Regulates Endothelial Cell Migration and Capillary Morphogenesis
Authors: Sorenson Christine M , Kondo Shuji , Tang Yixin , Sheibani Nader
Published: June 2021

Apoptosis plays a critical role during development and in the maintenance of multicellular organisms. B cell leukemia lymphoma 2 (bcl‐2) protects endothelial cells (EC) from apoptosis in response to a variety of stimuli. Previous work from this laboratory demonstrated attenuation of postnatal retinal vascular development and retinal neovascularization during oxygen‐induced ischemic retinopathy in bcl‐2 deficient (bcl‐2 −/−) mice. How bcl‐2 affects EC function during these processes require further investigation. To gain further insight into the functions of bcl‐2 in the endothelium we isolated retinal EC from bcl‐2 +/+ and bcl‐2 −/− mice. Retinal EC lacking bcl‐2 demonstrated reduced cell migration, reduced tenascin‐C expression, and reduced adhesion to vitronectin and fibronectin. The bcl‐2 −/− retinal EC also failed to undergo capillary morphogenesis in Matrigel. In addition, using an ex vivo angiogenesis assay we observed reduced sprouting from aortic rings grown in culture from bcl‐2 −/− mice compared to bcl‐2 +/+ mice. Furthermore, re‐expression of bcl‐2 was sufficient to restore migration and capillary morphogenesis defects observed in bcl‐2−/− retinal EC. Thus, bcl‐2‐mediated functions play an important role in EC migration and capillary morphogenesis during retinal vascular development and angiogenesis.
Erythropoietin enhances arteriogenesis rather than angiogenesis in infarcted rat heart
Authors: Imazuru Tomohiro , Matsushita Shonosuke , Tokunaga Chiho , Kanemoto Shinya , Enomoto Yoshiharu , Watanabe Yutaka , Hiramatsu Yuji , Sakakibara Yuzuru
Published: June 2021

Purpose: Erythropoietin (EPO) is a hormone regulating red blood cell production. Recently it is known that Epo enhances the angiogenesis. However, since shear stress is an initiator of arteriogenesis, Epo may increase arteriogenesis due to increased shear stress by erythrocytosis. From these backgrounds, we compared the effect of Epo on both angiogenesis and arteriogenesis. Methods: Myocardial infarction was prepared by LAD ligation in Wistar rat (Epo and control, each n=8). Epo (1,000 IU/kg) was administrated immediately after ligation. 4 weeks later, coronary angiography was performed using synchrotron radiation coronary microangiography. Numbers of vessels were also investigated by microscopy. Arteriogenesis was defined as number of arteriole (>100 um) and angiogenesis was defined as number of capillaries (<50 um). Results: Pathology: In capillary number, Epo increased 184% at border zone compared with intact area, whereas control increased 155% (p<0.05 vs. Epo). On the other hand, in arteriole number, Epo increased 594%, whereas control was 223% (p<0.00001 vs. Epo) in the same area. Angiography: Epo enhanced number of arterioles in border zone than control significantly (5.4+/−1.7 vs. 3.8+/−0.4 per 2 mm^2, p<0.05). Conclusion: Epo enhances arteriogenesis rather than angiogenesis in infarcted rat heart.
A motion‐based angiogenesis analysis to quantify new blood vessel growth
Authors: Tong Edmund Y. , Collins Geoffrey C. , Judkins Kyle M. , Greene‐Colozzi April E. , Chen Julia L. , Lee Joseph A. , Manos Philip D.
Published: June 2021

We developed a new method to quantify blood vessel growth using a short video recording of the vascular bed in the regenerated region of the zebrafish caudal fin. After cutting the three most ventral caudal fin bones at the point of branching, each zebrafish, Danio rerio, was exposed to an angiogenic factor for 60 minutes. On day six post amputation, after each fish was anesthetized with 0.2% Tricaine, the newly developed vascular bed in the regenerated area was examined under a Nikon microscope at 40X magnification and a 15 second video clip was recorded. The last 20 frames of the clip were then imported to an imaging software program called Environment for Visualizing Images 3.6 (ENVI 3.6). The only difference among these 20 frames was the movement of blood through all the blood vessels. Consequently, the deviation among the frames highlighted only the blood vessels. When only the newly developed vascular bed in the regenerated area was outlined, a precise, objective and easy comparison could be made between the angiogenic response in control and experimental zebrafish. The same method may be used to quantify angiogenic effects in other models with some modifications.
Megakaryocyte/platelet‐derived Neuropeptide Y (NPY), in addition to neuronal, is essential for ischemic revascularization in rodents
Authors: Tilan Jason Ulip , Everhart Lindsay M. , Abe Ken , Kitlinska Joanna , Herzog Herbert , Zukowska Zofia
Published: June 2021

Previously, we showed that sympathetically‐derived NPY promotes ischemic revascularization after femoral artery occlusion (FAO) in rodents by activating Y2 receptors (Rs) and dipeptidyl peptidase IV (DPPIV), which forms a Y2/Y5‐preferring agonist. The role of other NPY sources (platelets), Rs and temporal relationship to ischemic revascularization was unknown and is studied here. A critical role for NPY but not Y5R was shown in NPY−/− and Y5−/− mice whose post‐FAO limb revascularization was markedly impaired and unchanged, respectively. Within 5 days, FAO in rats (expressing platelet NPY) elevated plasma NPY levels (neuronal) and Y1, Y2, DPPIV and NPY mRNA (vs. non‐ischemic contralateral limb) in adductor (arteriogenesis zone) and gastrocnemius (angiogenesis zone) muscles; while density of CD31+‐capillaries fell. Vascular density, CD31+‐ and smooth muscle α‐actin+‐vessels, was restored by 14 days, when platelet levels doubled, and accelerated to 5 days by NPY slow‐release pellet (below FAO, 1 μg/14 days). Platelet NPY and bone marrow NPY mRNA were increased after FAO in platelet NPY‐expressing Sv129 WT mice, which were then used in a platelet depletion/transfer experiment [found (KA) to restore NPY atherosclerotic effects in resistant NPY−/−] with NPY−/−mice. Thus, early activation of neuronal and later activation of megakaryocyte/platelet‐derived NPY is essential for ischemic revascularization. NIH grants HL067357 and HL055310 to Z.Z.
Regulation of VEGF induced angiogenesis by β3 integrin through recruitment of VEGFR‐2 associated protein tyrosine phosphatase
Authors: Mahabaleshwar Ganapati H , Byzova Tatiana
Published: June 2021

Angiogenesis, the formation of new blood vessels from preexisting vasculature, occurs in a variety of physiological and pathological conditions. The process of angiogenesis is known to be regulated by vascular endothelial growth factor (VEGF) and its receptors (VEGFR‐2) in coordination with extracellular matrix interacting molecules such as integrins. Integrins have been reported to exhibit extracellular matrix dependent regulation of several tyrosine kinases on endothelial cell surfaces. In this study we have revealed the role of β3 integrin cytoplasmic tyrosine motifs in the regulation of protein tyrosine phosphatase (PTPs), associated with VEGFR‐2, in a tyrosine phosphorylation‐dependent manner. SHP‐2 association with VEGFR‐2 regulates the extent of basal and growth factor‐induced VEGFR‐2 phosphorylation in endothelial cells. Additionally, phosphorylated β3 integrin cytoplasmic tyrosine motifs provide binding sites for SHP‐2 and protect VEGFR‐2 from dephosphorylation. Moreover, DiYF endothelial cells, in which β3 integrin cytoplasmic tyrosine motifs are mutated to phenylalanine, exhibit deficient SHP‐2 binding to β3 integrin and VEGF stimulation, also display a modest decrease in SHP‐2 dissociation from VEGFR‐2 and decreased pathological angiogenesis in vivo. Further, we have also demonstrated that SHP‐2 binds to phosphorylated tyrosine residue 773 of the β3 cytoplasmic domain, and that β3 integrin cytoplasmic‐derived cell permeable prephosphorylated peptide 773Yp reduced VEGF‐induced VEGFR‐2 tyrosine phosphorylation and down stream signaling, endothelial cell migration, tube formation, ex vivo and in vivo angiogenesis. We have for the first time demonstrated this novel mechanism which regulates processes of VEGFR‐2 activation and pathological angiogenesis.
Intramyocardial transplantation of syngeneic fibroblasts expressing VEGF improves cardiac function post‐myocardium infarction in rats
Authors: Gonçalves Giovana Aparecida , Vassallo Paula Frizera , Cardoso Leandro , Santos Leonardo , Paulo Tucci José Ferreira
Published: June 2021

We tested the efficacy of modified cardiac fibroblasts (CF) expressing VEGF (vascular endothelial growth factor) and/or IGF‐1 (insulin‐like growth factor) associated to fibrin polymer to induce angiogenesis, vasculogenesis and improve cardiac function post myocardium infarction. The groups: VEHICLE= control, POLYMER= fibrin polymer, CELL= 106 CF, NULL, VEGF, IGF‐1 and IGF+VEGF= 106 modified CF by AdNULL, AdIGF‐1EGFP or AdVEGFEGFP, were directly injected in the left ventricle muscle of rats 24 h following ligation of the descending coronary artery. After 4 weeks, VEGF and IGF‐1 protein increased in IGF‐1, VEGF and IGF‐1+VEGF groups, p<0.0001. Interestingly, only groups receiving VEGF alone or combined with IGF‐1 increased capillary and vascular densities and reduced total myocardial collagen area (35,12 ± 7,05 vs. 31,28 ± 5,03 vs. 30,07 ± 6,21 vs. 25,89 ± 2,92 vs. 15,43 ± 2,02* vs. 16,07 ± 1,83%*, *p<0,05, respectively). Basal morphometric and functional cardiac indices remained unchanged in all groups; however, under pharmacologic stress, the VEGF groups displayed a significant improvement in cardiac work with maintenance of stroke volume and end‐diastolic pressure. Altogether, CF expressing VEGF alone or in combination with IGF‐1 can induce angiogenesis and vasculogenesis in ischemic myocardium decreasing collagen content and improving cardiac performance 4 weeks after coronary ligation.
A ligand to the mitochondrial benzodiazepine receptor prevents ventricular arrhythmias and LV dysfunction after ischemia or glutathione depletion
Authors: Brown David A , Aon Miguel A , Akar Fadi G , O’Rourke Brian
Published: June 2021

We examined how instability of mitochondrial membrane potential (ΔΨm) contributed to arrhythmogenesis and left ventricular dysfunction in intact hearts subjected to metabolic challenge. In isolated myocytes, oxidative stress was previously shown to elicit oscillations in ΔΨm which were stabilized by 4′‐chlorodiazepam (4‐ClDzp), a ligand to the mitochondrial benzodiazepine receptor. Guinea pig hearts were stressed either with global ischemia/reperfusion (I/R) or normoxic perfusion with diamide (to deplete the reduced glutathione pool). In both groups, overwhelming the anti‐oxidant defenses led to severe electrical and contractile dysfunction. Hearts exposed to I/R had high propensity for arrhythmias (score of 6.0 ± 0.7) and contractile dysfunction (LV developed pressure (LVDP) and LV minimum pressure at end of I/R: 10 ± 3 mmHg and 58 ± 1 mmHg, respectively). Stabilizing ΔΨm with 4‐ClDzp reduced arrhythmias (score 1.25 ± 0.25; P < 0.01) and contractile dysfunction (LVDP and LVP min were 23 ± 1 and 18 ± 3 mmHg at the end of I/R, respectively; P < 0.01). Similarly, diamide induced arrhythmias (score of 6.0 ± 1.1) that were prevented by co‐treatment with 4‐ClDzp (score of 1.0 ± 0.6; P < 0.01). LVDP also recovered significantly in diamide‐treated hearts plus 4‐Cldzp. These data provide further evidence that stabilizing ΔΨm in the face of oxidative stress has significant clinical implications for myocardial I/R injury.
CO2/HCO3 Modulates Receptor Protein Tyrosine Phosphatase Gamma (RPTPγ) Activity
Authors: Skelton Lara Ann , Boron Walter
Published: June 2021

RPTPγ is a type I tyrosine phosphatase receptor with an extracellular carbonic anhydrase‐like domain (γCAH) with 40% sequence identity to type‐α carbonic anhydrases. Carbonic anhydrases are highly efficient zinc metalloenzymes that catalyze the reversible hydration of CO2. However γCAH lacks two of three zinccoordinating histidine residues required for catalysis. We hypothesize that CO2 or HCO3, via γCAH, modulates the tyrosine phosphatase activity of RPTPγ. We expressed full‐length, HA‐tagged human RPTPγ in Xenopus oocytes and exposed single oocytes to HEPES (balance air, pH 7.50), or 5% CO2/33 mM HCO3 (balance air, pH 7.50) for 10 min, gently lysed the cell, and measured phosphatase activity using p‐nitrophenyl phosphate hydrolysis. Untreated or HEPES‐treated RPTPγ‐expressing oocytes have: (1) phosphatase activity well above that of uninjected or water‐injected controls and (2) a 300‐kDa band (detected by western blot) that is consistent with RPTPγ dimers. With RPTPγ oocytes, treatment with 5% CO2/33 mM HCO3 causes: (1) a ~4‐fold increase in phosphatase activity compared to treatment with HEPES and (2) the concurrent appearance of a 160‐kDa band. These results are consistent with the hypothesis that CO2 or HCO3 can induce monomerization and activation of RPTPγ.
Hb encapsulation in vesicles retards the reaction with NO, but not CO, by intracellular diffusion barrier
Authors: Sakai Hiromi , Tsuchida Eishun
Published: June 2021

NO‐binding of Hb is restricted by encapsulation in RBCs to prevent vasoconstriction. To clarify the mechanism, we analyzed Hb‐vesicles (HbV) with different intracellular Hb concentrations, [Hb] in, and different particle sizes using stopped‐flow spectrophotometry. The apparent NO‐binding rate constant, k′NO, of HbV at [Hb] in = 1 g/dl was almost equal to kNO of molecular Hb, indicating that the lipid membrane is not a barrier. With increasing [Hb] in to 35 g/dl, k′NO decreased to 1/3, which was further decreased to 1/5 with enlarging particle diameter (<450 nm). For CO‐binding, which is intrinsically much slower than NO‐binding, k′CO did not change greatly with [Hb] in and the particle diameter. Results obtained using diffusion simulations coupled with elementary reactions concur with these tendencies and clarify that NO is trapped rapidly by Hb from the interior surface area to the core of HbV at a high [Hb] in, retarding NO‐diffusion toward the core of HbV. In contrast, slow CO‐binding allows time for further CO diffusion to the core. Simulations extrapolated to a large particle (8 μm) showing retardation even for CO‐binding. The obtained k′NO and k′CO yield similar values to those reported for RBCs. In summary, the intracellular, not extracellular, diffusion barrier is predominant owing to the rapid NO‐binding that induces a sink of NO from the interior surface to the core, retarding further NO‐diffusion and binding.
Bioequivalence between inhaled hydrogen sulfide and intravenously administered sodium sulfide
Authors: VandenEckart Emily , Bengtsson Asa , Johnson Jeff , Mulligan JoAnne , Leviten Dina , Insko Michael , Mebel Elise , Vertz Peter , Toombs Christopher , Wintner Edward A , Szabo Csaba , Deckwerth Thomas
Published: June 2021

Hydrogen sulfide is best known as an environmental pollutant and human health hazard. Recently, sulfide has gained recognition as an endogenous biological mediator and is being examined for use as a therapeutic agent. As sulfide may be administered by both inhaled and parenteral routes, the question arises of how exposure to sulfide compares between the two modes of administration. Sprague Dawley rats were exposed for up to two hours of hydrogen sulfide gas up to 400 ppm or received up to 20 mg/kg sodium sulfide by continuous intravenous infusion. Sulfide concentrations in venous blood were quantified as sulfide dibimane derivative. Both modes of administration lead to a dose‐dependent elevation in blood sulfide concentrations over baseline concentrations and reached a new steady‐state concentration within two hours. Steady state blood sulfide concentrations show a simple linear relationship to hydrogen sulfide gas concentration or sodium sulfide dose. Identical blood sulfide concentrations can be achieved by either route of administration suggesting bioequivalency of hydrogen sulfide inhalation and sodium sulfide intravenous infusion in modulating blood sulfide concentrations. This suggests that both modes of administration may exert similar therapeutic effects.
Valsartan Regulates Interaction of Angiotensin II Type 1 Receptor and Endothelial Nitric Oxide Synthase via Src/PI3 K/Akt Signaling Pathway
Authors: Su Kuo‐Hui , Tsai Jin‐Yi , Kou Yu Ru , Wu Yuh‐Lin , Shyue Song‐Kun , Lee Tzong‐Shyuan
Published: June 2021

Valsartan, a selective angiotensin II type 1 receptor (AT1R) blocker, lowers blood pressure by causing vascular smooth muscle cell relaxation and nitric oxide (NO) production in endothelium. However, the underlying mechanisms of valsartan on NO production are not fully understood. In this study, we sought to investigate the molecular mechanism of valsartan in activation of endothelial nitric oxide synthase (eNOS) in bovine aortic endothelial cells (BAECs). Treatment with valsartan increased NO production in a dose‐ and time‐dependent manner, while the protein level of eNOS was not affected. Furthermore, valsartan increased the phosphorylated levels of Akt and eNOS proteins. Specific inhibitors were utilized to clarify the critical kinases involved in valsartan‐mediated eNOS activation. Our results showed that LY294002, a PI3 kinase antagonist and SU6656, a Src kinase family antagonist markedly suppressed valsartan‐induced eNOS phosphorylation and NO production. On the other hand, we also found valsartan treatment increased phosphorylation of AT1R on tyrosine residues and reduced association of eNOS and AT1R. Pretreatment with SU6656, but not LY294002 reversed this dissociation between eNOS and AT1R, implying the requirement of tyrosine phosphorylation on AT1R for valsartan‐mediated reduction of eNOS‐AT1R interaction. Take together, our findings suggest that valsartan induced eNOS activation through Src/PI3/Akt signaling pathway and regulation on AT1R‐eNOS interaction.
HYPOXIA INDUCIBLE FACTOR‐1 IMPROVES THE ACTIONS OF NITRIC OXIDE AND NATRIURETIC PEPTIDES AFTER SIMULATED ISCHEMIA‐REPERFUSION
Authors: Weiss Harvey R , Luciano Jason A , Tao Tan , Zhang Qihang , Huang Emily , Scholz Peter M
Published: June 2021

We tested the hypothesis that upregulation of hypoxic inducible factor‐1 (HIF‐1) would improve the negative functional actions of cyclic GMP in rabbit cardiac myocytes subjected to simulated ischemia [15 min 95% N2‐5% CO2]‐reperfusion [reoxygenation] to produce stunning. HIF‐1α was increased with deferoxamine (150 mg/kg/2 days). Shortening was examined after brain natriutetic peptide (BNP, 10−8, 10−7M) or S‐nitroso‐N‐acetyl‐penicillamine (SNAP, 10−6, 10−5M) and KT5823 (cGMP protein kinase inhibitor, 10−6M). In controls, BNP (−30%) and SNAP (−41%) reduced percent shortening, while KT5823 partially restored function (+18%). Deferoxamine‐control myocytes responded similarly. After stunning, BNP (−21%) and SNAP (−25%) reduced shortening less and KT5823 did not increase function (+2%). Deferoxamine increased the effects of BNP (−38%) and SNAP (−41%) in stunning and restored the KT5823 effect (+12%). The cGMP protein kinase increased protein phosphorylation in controls. Phosphorylation was reduced in stunning and restored after deferoxamine. Thus, ischemia‐reperfusion reduced the effects of cGMP and this was related to reduced cGMP protein kinase action. Increased HIF‐1α protects the functional effects of cGMP thorough maintenance of cGMP protein kinase activity after ischemic‐reperfusion.
Partial hindlimb occlusion during coronary artery occlusion reduces the susceptibility to ventricular arrhythmias via the intrinsic adenosine receptor system in conscious rats
Authors: Lujan Heidi L , DiCarlo Stephen E.
Published: June 2021

Temporary occlusion of coronary arteries can lead to potentially lethal arrhythmias. The arrhythmias are triggered directly by ischemia or during the reperfusion phase. Remote conditioning induced by ischemia in distant organs protects the heart from ischemic/reperfusion injury. However, the effect of remote conditioning on ischemia‐induced ventricular arrhythmias is unknown. Therefore, we tested the hypothesis that partial hindlimb occlusion during coronary artery occlusion reduces the susceptibility to ventricular arrhythmias. To test this hypothesis, 7 rats were instrumented for recording arterial pressure and ECG. A Doppler ultrasonic flow probe and vascular occluder were placed around the terminal aorta. Finally, a snare was placed around the left main coronary artery. The response to coronary artery occlusion during partial hindlimb occlusion was determined in conscious rats. Occlusion of the left main coronary artery resulted in tachy‐arrhythmias that culminated in ventricular fibrillation within 4.56 ± 0.15 min. Partial hindlimb occlusion during coronary artery occlusion culminated in ventricular fibrillation within 6.29 ± 0.49 min. Adenosine receptor blockade (theophylline, 10 mg/kg) attenuated the cardioprotective effects of remote conditioning (4.62 ± 0.79 min). Supported by HL67713
Spontaneous Reoxygenation of Myocardial Infarct Area with Permanent Coronary Obstruction
Authors: Wang Tiansheng , Moldovan Nicanor I. , Ilangovan Govindasamy , Talukder M.A. Hassan , Zweier Jay L.
Published: June 2021

Non‐refused areas of infarcted hearts are commonly thought to be severely hypoxic. However, the actual PO2 levels in the infarct area are not well known. This is critical for finding the best time and place of stem cells injection used in myocardial repair. We used electron paramagnetic resonance (EPR) and lithium phthalocyanine (LiPc) crystals as probes to measure PO2 in hearts at 1, 3, 5 and 7 days of permanent left anterior descending coronary artery (LAD) ligation in C57BL/6 mice (n=23). Immediately after LAD ligation, myocardial PO2 decreased from 20 mmHg to ∼0.8 mmHg, while at border zone remained significantly higher at ∼14 mmHg (P<0.01). Surprisingly, PO2 at infarct area started to increase after 3‐day and remained stable at ∼ 40mmHg after 5 days. At border zone, PO2 increased to ∼40mmHg after 1‐day ligation. About 40% of mice with infarction died of left ventricular rupture that occurred on average at 4.4±0.8 days, similar to control mice without LiPc injection (n=40). However, the pattern of PO2 was indistinguishable between ventricular ruptured and surviving mice up to the 4th day. To our knowledge, this is the first documentation of spontaneous reoxygenation of infarct area after LAD ligation in mice. This suggests that an optimal time for stem cell injection in the infarct zone‐based on myocardial oxygenation‐would be 3∼4 days after onset of ischemia, while the border zone is a preferable site at earlier times.
Functional consequences of overexpression of ETA in adult rat ventricular myocytes
Authors: Chung Ka Young , Walker Jeffery W
Published: June 2021

Activation of ETA, the predominant ET‐1 receptor subtype in myocardium, is known to induce a positive inotropic effect (PIE). In heart failure, ETA is often upregulated presumably as a compensatory measure. In this study, we explored functional consequences of upregulation of ETA in adult rat ventricular myocytes (ARVM). To investigate physiological function, we examined three twitch parameters (PIE, diastolic shortening and twitch broadening) and measured [Ca2+]i in control and ETA overexpressed ARVM. In control ARVM, ET‐1 induced ~30% PIE and ~1% diastolic shortening, but twitches were not broadened. Overexpression of ETA significantly increased PIE to ~60%, diastolic shortening to ~7% and twitch broadening by ~15%. Peak [Ca2+]i and basal [Ca2+]i correlated with PIE and diastolic shortening respectively, but the slopes were larger in ETA overexpressed ARVM. Therefore, changes in [Ca2+]i induced significantly more twitch responses in ETA overexpressed ARVM. These results suggest that ETA‐overexpression has a substantial impact on the twitch properties including i) prolongation of twitch duration, and ii) an increase in diastolic cell shortening. Such ET‐1 effects mediated through upregulated ETA may contribute to diastolic dysfunction (delayed relaxation and elevated ventricular end diastolic pressure) in heart failure.

This study is supported by an AHA Predoctoral fellowship and NHLBI.
Abnormalities in the catabolic fate of long‐chain fatty acids and glucose in compensated murine cardiac hypertrophy
Authors: Wambolt Richard B , Parsons Hannah L , Bohunek Lubos , Allard Michael F
Published: June 2021

Reduced oxidative catabolism of fatty acids (FAO) and accelerated rates of non‐oxidative glucose catabolism (NOG) are recognized metabolic abnormalities in genetic and acquired models of cardiac hypertrophy (H) in rats, but are less well characterized in mice. We determined catabolic fates of long‐chain fatty acid (palmitate – P) and glucose (G) in compensated non‐hypertrophied (C) and hypertrophied (H) hearts from sham‐operated and abdominal aortic‐constricted CD1 mice. Hearts were perfused with either 1.2mM P, 5.5mM G, 0.5mM lactate and 20mU/L insulin (Series 1) or 0.6mM P, 5.5mM G, 1.5mM lactate, 0.5mM pyruvate and 20mU/L insulin (Series 2 ‐ reflects in vivo substrate concentrations in mice). No differences in heart function, expressed as cardiac power (ml·mmHg·min−1), were observed between C and H in either Series 1 (10.9 ± 0.6 vs. 10.4 ± 0.3) or Series 2 (12.8 ± 0.4 vs. 13.1 ± 0.6).

Results:

Substrate catabolism in a murine model of acquired compensated H resembles that in models of H in rats. Abnormalities in NOG persist in hearts exposed to a physiologically relevant substrate mixture, even though significant differences in FAO disappear, suggesting that defects in NOG are a key metabolic abnormality occurring early in the development of H.
Mitochondrial MMP activation decreases myocyte contractility in hyperhomocysteinemia.
Authors: Moshal Karni S , Metreveli Naira , Kumar Munish , Vacek Thomas , Tyagi Neetu , Tyagi Suresh
Published: June 2021

Hyperhomocysteinemia (HHCY) is associated with mitochondrial dysfunction. Matrix metalloproteinase protease (MMP) activation causes mitochondrial dysfunction. We tested the hypothesis that HCY activates myocyte mitochondrial MMP (mtMMP), induces mitochondrial permeability transition (MPT), and causes contractile dysfunction. Mice were administered HCY (0.6g/L) in drinking water for 10 wks. The mtMMP activity was measured by zymography. MPT was measured by decrease in light absorbance at 540 nm. Cellular calcium transients were detected using IonOptix edge detection system. The effect of MK‐801(NMDA‐R1 blocker), GM6001 (MMP blocker), and cyclosporine A (MPT blocker) on myocyte contractility was evaluated. HHCY induced the mtMMP‐9 and caused MPT. Calcium decay was faster in WT compared to HHCY. A decrease in cell shortening, maximal rate of contraction (−dL/dt), and maximal rate of relaxation (+dL/dt) was observed in HHCY (Fig. 1). Furthermore, HHCY‐induced decrease in cell shortening, −dL/dt, +dL/dt was attenuated with MK‐801, GM6001, and cyclosporine A. We conclude that HHCY activates mtMMP‐9, increases MPT leading to decrease in contractility by activating NMDA‐R1. This study was supported by AHA post‐doctoral training to KSM and NIH to SCT.
The effect of hypergravity environment on vestibulo‐cardiovascular reflex in conscious rats
Authors: Abe Chikara , Tanaka Kunihiko , Awazu Chihiro , Morita Hironobu
Published: June 2021

We have demonstrated that the vestibular system has a significant role in the arterial pressure (AP) response during gravitational change in conscious rats. The vestibular system is known to be highly plastic; i.e., the plasticity of the vestibulo‐ocular and vestibulo‐spinal reflex. Resent study from our laboratory demonstrated the plasticity of the vestibulo‐cardiovascular reflex. Microgravity‐induced pressor response was significantly attenuated if 8 weeks old rats were reared under 3 G environment for 2 weeks. Thus, the vestibulo‐cardiovascular control system which was constructed under 1 G environment was altered by 3 G environment for 2 weeks. However, it is still unclear whether the AP response via the vestibular system might be altered if the vestibulo‐cardiovascular control system is constructed under different gravitational environment. Accordingly, the aim of the present study was to examine whether the vestibular‐mediated AP response might be altered if rats were born and developed under hypergravity environment. To examine this, the AP response to linear acceleration was examined in conscious rats which were born and developed under usual 1 G or 2 G condition. ± 1 G linear acceleration of four directions, in which tail‐to‐nose, nose‐to‐tail, left‐to‐right and right‐to‐left acceleration, was employed. The AP of the 1‐G rat was increased by 24 ± 1 mmHg in the tail‐to‐nose, 19 ± 1 mmHg in the nose‐to‐tail, 20 ± 1 mmHg in the left‐to‐right and 21 ± 1 mmHg in the right‐to‐left acceleration. This pressor response was significantly attenuated in the 2‐G rat in all directions. However, there was no significant difference in the AP response during air jet stimulation between 1‐G and 2‐G rats. These results indicate that the vestibulo‐cardiovascular control system was specifically altered if rats were born and developed under 2 G environment.
Prevention of Orthostatic Intolerance after Exposure to Microgravity: Exercise Countermeasure and Volume Loading
Authors: Shibata Shigeki , Perhonen Merja , Prasad Anand , Hastings Jeff , Palmer Dean , Levine Benjamin D.
Published: June 2021

Prolonged exposure to microgravity leads to hypovolemia and cardiac atrophy, both of which contribute to orthostatic intolerance on return to earth. We hypothesized that an exercise countermeasure (90 min/day, 75% max HR) would prevent the cardiac atrophy after exposure to simulated microgravity (6 degree head‐down bed rest) while an exercise countermeasure with volume loading at the end of bed rest (up to pre‐bed rest blood volume and left ventricular (LV) filling pressure) would preserve the orthostatic tolerance. To test these hypotheses subjects were randomly assigned into three groups (N=7 in each group): exercise group (Ex), Dextran infusion group (Dx) and exercise plus Dextran infusion group (Ex+Dx). Cardiac remodeling was evaluated by LV muscle mass with MRI and pressure‐volume relationship of LV. Orthostatic tolerance was evaluated by a max LBNP test. Measurements were made pre and post 2‐wk bed rest. LV mass increased by 5% and pressure‐volume curves were similar after bed rest in both Ex and Ex+Dx, while a decrease of LV mass by 4% and left‐ward shift of the pressure‐volume curve were observed in Dx alone. Orthostatic tolerance was only maintained in Ex+Dx after bed rest, which decreased in EX alone by 42% and in Dx alone by 25%. Preserved LV morphology with restoration of normal blood volume appears to be necessary to prevent orthostatic intolerance after exposure to microgravity. Supported by NSBRI
Induction of NEDD4 under simulated microgravity
Authors: Fiedorowicz Katarzyna , Azevedo Luis Da Silva , Zakrzewicz Andreas , Pries Axel Radlach
Published: June 2021

Vascular endothelial cells are exposed to mechanical forces e.g. wall shear stress, wall tension, and pulsatile stretch, which are modulated by the gravitational field. The effects of microgravity may influence endothelial cell function including protein synthesis and degradation.Therefore, this study was designed to investigate microgravity dependent effects on the ubiquitin‐ligase NEDD4 in endothelial cells. In order to produce microgravity endothelial cells (EA hy926, HUVEC) were seeded on microcarriers and cultured in the Rotating Wall Vessel for 24 h and 48 h. Controls were kept under normal gravity or exposed to shear stress using a cone and plate apparatus (6 dyn\cm2, 24 h). Gene expression and protein concentration were analysed by real‐time RT‐PCR and Western blotting, respectively. Our results indicate that NEDD4 is upregulated to 200% under microgravity and downregulated to 70% by shear stress relative to controls (1G, no shear). The present data suggest that NEDD4 is sensitive to mechanical forces; the induction under microgravity may be a mechanism to enhance protein degradation in endothelial cells.