bluuebunny/crossref_metadata_2025 huggingface dataset:
Elevated renin and enhanced adrenal steroidogenesis in the Ossabaw swine model of the metabolic syndrome
Authors: Aloosh Mouhamad , Pratt J. Howard , Sturek Michael , Basile David
Published: June 2021

The Ossabaw pig fed an atherogenic diet develops features of the metabolic syndrome (MetS). We hypothesized that development of MetS in Ossabaw swine would result in increased activation of the renin‐angiotensin aldosterone system (RAAS) and development of hypertension. Male Ossabaw swine (∼20 weeks age) were fed excess atherogenic diet for 55 weeks, resulting in robust MetS characterized by obesity, insulin resistance, dyslipidemia and hypertension. Serum creatinine and urea nitrogen levels were reduced in MetS vs lean controls (∼13 and 48 %, p<0.05), suggesting renal hyperfiltration. Plasma renin activity in fasting, unstressed animals was higher (0.5 ± 0.2 vs 2.9 ± 0.5 ng Ang I ·ml−1· min−1) in MetS pigs relative to lean controls. Aldosterone levels were also elevated ∼6‐fold in MetS pigs. An additional group of pigs fed atherogenic diet for 9 weeks was used to measure adrenal responsiveness in early MetS. Ang II (5 ng·kg−1·min−1) or ACTH (2 ng ·kg−1·min−1) infusion into conscious MetS pigs resulted in significantly greater peak aldsosterone secretion relative to lean controls. Taken together, the data suggest that the development of MetS in Oss pigs leads to an alteration in renal function and renin and aldosterone secretion are enhanced in this setting; the latter may be secondary to increased Ang II and possibly increased adrenocortical sensitivity.(Support: NIH RR013223, HL062552).
Osmotic stimulation of renin release from single mouse juxtaglomerular cells
Authors: Skott Ole , Jensen Boye L. , Madsen Kirsten , Jorgensen Finn , Hansen Pernille B. , Friis Ulla G.
Published: June 2021

We tested whether cell swelling stimulates renin release from juxtaglomerular cells (JG) via activation of the prostaglandin system. Lowering osmolality by 10 mOsm/kg led to a 20‐fold increase in renin release from superfused JG cells. The whole cell patch clamp approach was used to measure cell membrane capacitance (Cm) as an index of exocytosis. Exposure of single JG‐cells to 3.6% and 5.5% hypotonic solution led to increases in Cm of 7±1.8% (n=5) and 8.3±1.4% (n=8) that were blocked by indomethacin (n=4) and which were absent in JG‐cells from COX‐2−/− mice. In COX‐2+/+ littermates, a 5.5% hypotonic solution led to a significant increase in capacitance (8.5±2.2%, n=4). JG cells from COX 2−/− mice responded to external PGE2 with a significant increase in capacitance. Hypotonic treatment (5, 10 and 20% reduction in osmolality) enhanced the production of cAMP in isolated JG cells. Intracellular dialysis of the protein kinase A inhibitor RpcAMPs (25 μM) in the patch pipette blocked the ability of hypotonic treatment to increase cell membrane capacitance. Consistent with cAMP‐induced activation of BKCa channels by hypotonic treatment, an enhanced outward current was observed at positive potentials. We suggest that cell swelling stimulates renin release from single juxtaglomerular cells by activation of COX‐2, release of PGE2, and activation of cAMP‐coupled EP‐receptors.
Noninvasive transcutaneous bionic baroreflex system prevents severe orthostatic hypotension in patients with spinal cord injury
Authors: Yoshida Masayoshi , Chishaki Akiko , Saitou Toshirou , Kimura Satoshi , Andoh Makoto , Tsutsumi Takaki , Shiba Keiichiro , Murayama Yoshinori , Sunagawa Kenji
Published: June 2021

Background:

Central baroreflex failure in patients with spinal cord injuries (SCI) results in serious orthostatic hypotension (HYPO). Since somatic inputs affect sympathetic activities, we examined if the bionic mechanism (Circulation 1999) using transcutaneous electrical stimulation regulates arterial pressure (AP) in those patients.

Methods and Results:

In 12 SCI patents with HYPO, we identified skin regions capable of increasing AP in response to electrical stimulation. By a square wave approach, we determined the transfer function from the skin stimulation to BP response. Using the transfer function (gain=1.95±0.62 mmHg/msec, τ=75.3±13.1 sec, lag=0.39±0.37 sec), we designed the bionic regulator (BIONIC) to feedback control AP. Orthostatic stress decreased mean AP by 30.7±2.9 mmHg. Activation of BIONIC immediately restored AP to a prespecified level (mean AP recovery=26.2±1.9 mmHg).

Conclusion:

The transcutaneous bionic mechanism is noninvasive and capable of stabilizing AP in patients with serious central baroreflex failure. The oriental wisdom, i.e., making the use of a skin as a window to talk to the autonomic system, revitalizes patients with central baroreflex failure.
Cardio‐postural interactions and aging
Authors: Blaber Andrew P. , Landrock Clint , Souvestre Philippe A.
Published: June 2021

Introduction: Until recently cardiovascular and postural reflexes have been looked at as independent control systems. In this study we propose an interaction between these two systems, particularly in relation to the maintenance of venous return through skeletal muscle pump in conditions of impaired vascular control or increased venous pooling. We investigated this “cardio‐postural” interaction with aging. Methods: Healthy elderly and young subjects were tested in a sit to stand test. Mediolateral centre of pressure (COP) trajectory, as well as non‐invasive heart rate and blood pressure data were collected in two test conditions (eyes open or eyes closed) in randomized order. Data was collected in over a 10 minute period in two equal phases (sitting followed by standing). A power spectral density analysis was performed for mediolateral sway and BP for each subject. Results: Postural sway power was higher in elderly subjects with distinctive low frequency peaks (<0.1 Hz) that matched peaks found in blood pressure. Both COP and BP data had variation in the higher frequency range (0.15–0.25 Hz) that corresponded to respiration. The observed increase, with age, in postural sway in a region corresponding to low frequency blood pressure variation may represent an increase in skeletal muscle pump activity to maintain blood pressure in the elderly due to a reduction in baroreflex with age. Funded by Simon Fraser University.
Inhibition of the PI3 Kinase Signal Transduction Pathway in Nucleus Tractus Solitarii of (mRen2)27 Transgenic Rats improves Baroreceptor Sensitivity
Authors: Logan Exazevia , Diz Debra , Ganten Detlev , Ferrario Carlos , Averill David
Published: June 2021

The phosphoinositol kinase (PI3K) pathway plays a role in the maintenance of resting mean arterial pressure (MAP) in vivo but the exact mechanisms remain unclear. Our goal was to determine whether the PI3K pathway modulates arterial baroreceptor reflex sensitivity (BRS) via actions in the solitary tract nucleus (nTS) of (mRen2)27 transgenic hypertensive rats. Male Hannover Sprague‐Dawley (HnSD) and (mRen2)27 rats (9–20 wk old) were anesthetized with urethane/chloralose. MAP was measured before and after bilateral nTS microinjections of the PI3K inhibitor wortmannin (100 nmol/L, 50nL). BRS was assessed before and after wortmannin treatment by intravenous infusion of increasing concentrations of phenylephrine to elicit changes in MAP and heart rate. NTS injections of wortmannin in (mRen2)27 rats significantly decreased in MAP (−32 ± 6 mm Hg; n = 5) for ~90 minutes. Wortmannin failed to decrease MAP in HnSD rats (−4 ± 3 mm Hg; n = 5). BRS improved following wortmannin treatment in (mRen2)27 rats (0.2 + 0.1 vs 0.7 ± 0.2 msec/mm Hg; p < 0.05); however the BRS of HnSD rats decreased (2.1 ± 0.5 vs 1.2 ± 0.5 msec/mm Hg; p < 0.05) following PI3K blockade. These results demonstrate that the PI3K pathway in the nTS of hypertensive rats impairs BRS and contributes to elevation of MAP. Further studies are required to determine the mechanisms responsible for the differences in direction of changes in BRS between (mRen2)27 and HnSD rats.
EXERCISE TRAINING REDUCES BLOOD PRESSURE AND GLOMERULOSCLEROSIS IN SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Neto Octavio Barbosa , Bichuette Fabiano , Silva Debora Tavares Resende e , Reis Marlene Antônia , Silva Valdo José Dias da
Published: June 2021

The aim of the study was to assess the effects of exercise training on baseline arterial pressure (AP), heart rate (HR), autonomic tonus and renal morphology in spontaneously hypertensive rats (SHR). Twenty five male 48–50 weeks‐old SHRs were submitted or not to a swimming protocol, hypertensive sedentary (HS, n=12) and hypertensive trained (HT, n=13) rats. After training, all animals, under anesthesia, had their femoral vessels cannulated. After twenty‐four hours, AP was recorded in baseline conditions during 30 minutes. Following, autonomic blockade of heart was performed using atropine and propranolol. At the end, animals were euthanized and their kidneys were excised for morphologic analysis. Exercise training was able to reduce baseline mean AP (MAP) and HR (123±3 mmHg/334±5 in HT versus 181±4 mmHg/397±9 bpm in HS, p<0.05, respectively). The HT group presented decrease in sympathetic tonus (51±16 bpm versus 138±9 bpm in HS, p<0,05) and increase in vagus tonus (−33±7 bpm versus ‐10±6 bpm in HS, p<0,05). In addition, HT group exhibited smaller glomerulosclerosis indexes (0.07±0.4%) in comparison to HS group (0.13±0.3%, p <0.05). These data indicate that the reduction of baseline AP and HR observed after exercise training affected several autonomic indexes, suggesting a shift of autonomic balance towards a vagal predominance to the heart, which was associated to a concomitant decrease of renal lesions.
Renal denervation eliminates the natriuretic effect of isotensive sodium loading in conscious rats
Authors: Bie Peter , Huang Chunlong , Wolff Helle , Johns Edward J. , Kompanowska‐Jezierska Elzbieta
Published: June 2021

It was hypothesized that the renal nerve activity (RNA) mediates the natriuretic response to an infusion of NaCl, which does not change mean arterial blood pressure (MABP). This was tested in trained rats supplied with appropriate chronic instrumentation. NaCl solution (1 M) was infused i.v. at 0.02 ml/min/kg (4–5 μl/min) for 2 h during measurements of circulatory, endocrine, and renal variables including RNA. During NaCl infusion RNA decreased by 15% (p<0.05) within 30 min of infusion and reached a nadir of −25% (p<0.05). Renal denervation per se decreased MABP by 15.5 mmHg (p<0.01). In sham operated rats, NaCl infusion increased plasma Na+ by 1.6 mmol/l (repeated measures ANOVA, p<0.03) but left MABP unchanged while heart rate (HR) decreased (455±7 to 427±7 bpm, p<0.0001). Urine flow tended to increase (p=0.056); sodium excretion increased 4‐fold (1.4±0.2 to 6.0±0.6 μmol/min, p<0.0001) while potassium excretion remained stable (2.2±0.3 to 2.3±0.4 μmol/min). NaCl infusion to renally denervated rats decreased HR similarly (423±17 to 393±20 bpm, p<0.005). In contrast, however, sodium excretion remained constant (2.2±0.8 to 3.9±0.9, p=0.68) despite a significant increase in MABP (102±3 to 109±3 mmHg, p<0.0001). It is concluded that a physiological sodium load increases sodium excretion by mechanisms dependent on renal nerves.

Supported by the Danish Medical Research Council and the Novo Nordisk Foundation.
The contribution of the sympathetic nervous system to the stress‐induced pressor and tachycardic hyperresponsiveness programmed by prenatal high salt
Authors: Porter James Paul , King Summer , Petrini Michael , Rau Michael
Published: June 2021

Adult female offspring of rats fed high salt during pregnancy exhibit hyperactive pressor and tachycardic responses to acute stress. In this study, we sought to determine if blockade of sympathetic receptors would prevent this enhanced response to stress. Sprague Dawley rats were fed 8% NaCl (HS) or 0.7% NaCl (NS) during pregnancy. After delivery, all mothers were fed standard normal‐salt chow. Adult female offspring (10 weeks) received radiotelemetry probes for recording of mean arterial pressure (MAP) and heart rate (HR). Two weeks later, rats were injected with a mixture of the ganglionic blocker, cholrisondamine (5 mg/kg), and the beta‐adrenergic antagonist, propranolol (6.5 mg/kg, ip), 15 min prior to being placed in restraining tubes. MAP and HR were recorded every 5 min during 30 minutes of restraint and 30 minutes of recovery. Combined blockade prevented the rise in HR induced by restraint, and the difference between NS and HS rats was abolished. Much of the pressor response to restraint was also prevented by the combined treatment in both groups, but the HS rats still had a significantly increased MAP compared to NS rats during restraint and recovery. This suggests that a programmed sympathetic hyperactivity to stress may explain the enhanced tachycardic response in HS offspring. However, the enhanced pressor response may include changes in other control systems. Supported by AHA, Western States Affiliate.
Increased sympathetic activity in rats submitted to chronic intermittent hypoxia (CIH) is coupled to enhanced late expiratory activity
Authors: Zoccal Daniel B , Simms Annabel E , Bonagamba Leni GH , Braga Valdir A , Pickering Anthony E , Paton Julian FR , Machado Benedito H
Published: June 2021

The mechanisms triggering the sympathetic overactivity in CIH rats are not understood. In the present study, we explored whether juvenile rats exposed to CIH exhibit changes in central respiratory‐sympathetic coupling. CIH was induced with 6% O2 for 40 s every 9 min, 8 h/day for 10 days. On the 11th day, awake CIH rats breathing room air showed a higher mean arterial pressure than controls (101 ± 3 vs 89 ± 3 mmHg, n = 14). Recordings of phrenic, thoracic sympathetic (tSNA), cervical vagus (cVN) and abdominal nerve (Abd) activities were made in the working heart‐brainstem preparation. During late expiration (Late E), tSNA was greater in CIH (n = 9) than in control rats (52 ± 5 vs 40 ± 3%, n = 11; P < 0.05). Moreover, CIH rats (n = 6), but not controls (n = 5), also exhibited a peak of activity in Abd during Late E with reduced post‐inspiratory activity in cVN. These observations suggest that CIH alters the breathing pattern evoking Late E activity in the Abd. We propose that this Late E discharge in CIH rats contributes with an additional excitatory synaptic drive to the sympathetic outflow and, in turn, raises arterial pressure. Further studies are required to identify the neuronal populations and the correspondent neurochemical mechanisms responsible for the altered respiratory‐sympathetic entrainment in CIH rats. Supported by CNPq and FAPESP (Brazil) and BHF (UK).
Spinal nociceptin mediates electroacupuncture‐related modulation of visceral sympathoexcitatory reflex response in rats
Authors: Zhou Wei , Mahajan Aman , Longhurst John
Published: June 2021

This study investigated the importance of nociceptin in the visceral reflex modulation during electroacupuncture (EA). Cardiovascular pressor reflex responses were induced by gastric distension (GD) in anesthetized Sprague‐Dawley rats. Intrathecal injection of nociceptin (10 nM) at T2‐3 attenuated the GD‐induced pressor responses by 37 ± 5% similar to the influence of EA at P 5–6 acupoints for 30 minutes (42 ± 7% decrease). Intrathecal injection of the nociceptin antagonist, [N‐Phe1]‐nociceptin (1–13) NH2, partially reversed the EA response by 67%. Pretreatment with the opioid receptor antagonist naloxone did not alter the EA‐like inhibitory effect of nociceptin on the pressor reflex, while a combination of nociceptin receptor antagonist with naloxone completely abolished the EA effect. Intrathecal injection of nociceptin attenuated the pressor responses to electrical stimulation of the rostral ventrolateral medulla by 46% suggesting that nociceptin acts in efferent pathways. Immunoreactivity for nociceptin was observed in neurons in the superficial laminae of the dorsal horn, ventral horn and intermediolateral column (IML) of the spinal cord. Furthermore, EA at P 5–6 activated nociceptinergic neurons in the IML and the dorsal horn. These results suggest that nociceptin in the spinal cord mediates the visceral reflex responses, likely through its effect on both afferent and efferent pathways.
Intermittent postural recovery during 14 days of hindlimb unloading (HU) is not sufficient to restore cardiac autonomic imbalance in rats
Authors: Moffitt Julia Ann , Beltz Terry G. , Johnson Alan Kim
Published: June 2021

Previous data indicate that 14 days of continuous HU in rats produces cardiac autonomic imbalance. We hypothesized that a daily period of normal posture may resolve these effects. Male, Sprague‐Dawley rats were randomly assigned to control (CC; n=3), continuous HU (HUC; n=4) or intermittent HU (HUI; n= 5) groups. Control rats were maintained in the normal posture. HUC rats underwent continuous elevation of the hindlimbs for 14‐days while HUI rats were returned to the normal posture for 30 minutes each day during the HU procedure. On the 14th day, mean arterial pressure (MAP) and heart rate (HR) were measured followed by selective cardiac autonomic blockade administered via i.v. injection of methylatropine and propranolol. Both HU groups exhibited significant resting tachycardia compared to CC rats, but HR was lower in HUI vs. the HUC group (CC: 366±3.9; HUC 474±7.5; HUI: 434±1.6 bpm). However, both HU groups had significantly less parasympathetic (CC: 60±7.7; HUC: 25±10.9; HUI: 15±5.2 Δbpm) and greater sympathetic cardiac tone (CC: 16±7.9; HUC: 91±10.9; HUI: 77±9.2 Δbpm) than CC rats, with no difference between HU groups with respect to either autonomic parameter. Baseline MAP was not different among any of the groups. Data indicate that while daily recovery from HU may partially restore resting HR, it is not a sufficient stimulus to reverse the autonomic imbalance produced by HU‐induced deconditioning. (Supp. by: NIH HL14388 & DK 066086).
Effect of stellate ganglionectomy (SGx) on the long‐term responses of arterial pressure (AP) and heart rate (HR) to beta‐1 adrenergic blockade in conscious rats
Authors: Yoshimoto Misa , Novotny Martin , Babankova Dasa , Swain Gregory M , Wehrwein Erica A , Kreulen David , Osborn John
Published: June 2021

Alterations in cardiac sympathetic outflow and norepinephrine reuptake are associated with many diseases, including hypertension. However, relatively little is known about the direct role of cardiac sympathetic innervation on regulation of cardiovascular function in conscious animals. Therefore, we examined the effect of chronic denervation of the heart by SGx on regulation of AP and HR in conscious rats. Rats were instrumented for telemetric measurement of AP and HR. After 5 control days, rats were subjected to SGx (N = 9) or SHAM (N = 8) surgery. 7 days later both groups were administered the beta‐1 adrenergic antagonist, atenolol, for 5 days. AP (mmHg) was nearly identical in both groups during the entire protocol including control (SGx; 99 ± 1, SHAM; 98 ± 1), Day 6 after SGx (95 ± 1) or Sham (96± 2), and Day 5 of atenolol (SGx; 90 ± 1, SHAM; 88 ± 1). HR (beats/min) was similar in both groups during control (SGx; 402 ± 6, SHAM; 393 ± 7) but significantly lower 6 days after SGx (337 ± 4) compared to Sham (369 ± 9). By Day 5 of atenolol HR was similar in SGx (308 ± 4) and Sham (310 ± 11) rats. Measurement of tissue norepinephrine (NE) content at the end of the study showed negligible levels of NE in all 4 cardiac chambers of SGx compared to Sham hearts. We conclude that; 1) SGx decreases basal HR but has negligible effects on long‐term regulation of AP and 2) the hypotensive response to atenolol is not mediated by its actions on the heart in normal rats. Supported by NIH Grant HL064178.
Contributions of baro‐ and chemoreceptors in mediating the hypertensive response to bilateral carotid occlusion in conscious mice
Authors: Lataro Renata Maria , Castania Jaci Airton , Chapleau Mark W. , Salgado Helio Cesar , Fazan Rubens
Published: June 2021

This study aimed to characterize the hypertensive response to bilateral carotid occlusion (BCO) in conscious C57BL mice and differentiate the role played by baro‐ and chemoreceptors in this response. Under tribromoethanol anesthesia, mice were implanted with pneumatic cuffs around the common carotid arteries and a femoral artery catheter for measurement of arterial pressure. In the same surgery the mice were submitted to aortic (n=7) or carotid sinus (n=5) denervation, or sham surgery (n=6). BCO (30 s) elicited a prompt rise in mean arterial pressure that was sustained throughout the period of occlusion. The hypertensive response to BCO from sham‐operated mice (40±5 mmHg) was not significantly different than that observed in aortic‐denervated mice (48±3 mmHg), but was much greater than that observed in carotid sinus denervated mice (15±3 mmHg). In separate groups of mice, suppression of chemoreceptor activity by ventilation with 100% O2 (PaO2>500 mmHg) attenuated the hypertensive response to BCO in sham‐operated mice (30±6 vs. 51±5 mmHg, n=7) but did not alter the response in carotid sinus denervated mice (20±4 vs. 18±3 mmHg, n=6). The results of the present study indicate that the hypertensive response to BCO in conscious mice is mediated by both baro‐ and chemoreceptors and, in contrast to the rat, the aortic baroreceptors play a minimal role in buffering the hypertensive response to BCO in mice. CNPq, FAEPA.
TRPV1‐mediated sympathetic responsiveness in hindlimb muscle ischemia
Authors: Xing Jihong , Gao Zhaohui , Lu Jian , Sinoway Lawrence , Li Jianhua
Published: June 2021

Muscle metabolic by‐products stimulate thin fiber muscle afferent nerves and evoke reflex increases in blood pressure and sympathetic activity. We report that chemically sensitive transient receptor potential vanilloid type 1 (TRPV1) channels present on sensory muscle afferent neurons have an important impact on sympathetically mediated cardiovascular responses. In turn responses are exaggerated by an ischemic insult to the muscle. Muscle ischemia was induced by the femoral artery ligation in rats. Our data show that 1) ischemia leads to upregulation of TRPV1 expression in the dorsal root ganglion (DRG); 2) the magnitude of the DRG neuron TRPV1 response induced by capsaicin is greater after ischemia (2.9±0.23 in control vs. 3.9±0.31 nA after ischemia, P<0.05); and 3) RSNA and MAP responses to capsaicin are also enhanced after chronic ischemia (54±11%, 9±3 mmHg in controls vs. 98±13%, 33±5 mmHg after ischemia, P<0.05). These results reveal a novel receptor mechanism by which muscle metabolites enhance the reflex sympathetic responses after the induction of chronic ischemia. Thus, alternations in TRPV1 can contribute to enhanced sympathetically mediated vasoconstriction leading to reduced muscle blood flow and exercise intolerance under circumstances of chronic muscle ischemia associated with a number of disorders such as peripheral vascular disease. (Supported by R01 HL075533, R01 HL078866 and R01 HL060800)
Effects of emotional and mental stress on muscle sympathetic nerve activity in humans
Authors: Durocher John J , Kern Rosalie P , Carter Jason R
Published: June 2021

Mental stress consistently increases arterial blood pressure and heart rate, but sympathetic neural responses remain controversial. The purpose of this study was to investigate cardiovascular and neural responses to viewing negative pictures, and compare those responses to a standard mental stress protocol. Muscle sympathetic nerve activity (MSNA), mean arterial pressure (MAP), heart rate (HR), and perceived stress levels were recorded in 12 healthy men in the prone position during three trials: 1) neutral pictures, 2) negative pictures, and 3) mental arithmetic. MAP and HR increased during mental arithmetic (Δ13±3 mmHg and A13±2 beats/min; P<0.001), but did not change during negative or neutral pictures. MSNA did not change during neutral pictures (Δ2±l bursts/min; n=11), negative pictures (Δ0±l bursts/min; n=11), or mental arithmetic (Δ0±l bursts/min; n=8). MSNA increased during recovery from mental arithmetic (Δ4±2 bursts/min; P<0.05), but did not change during recovery from negative or neutral pictures. Perceived stress levels increased more dramatically during mental arithmetic (3±0 a.u.) compared to negative pictures (2±0 a.u.; P<0.001). These findings demonstrate that emotional stress evoked by negative pictures does not alter cardiovascular and muscle sympathetic neural activity in humans, and challenges the concept that the perception of stress modulates MSNA responses to mental stress in humans.
Progressive Muscle Metaboreflex Activation Gradually Decreases Spontaneous Heart Rate Baroreflex Sensitivity During Dynamic Exercise
Authors: Sala‐Mercado Javier A. , Ichinose Masashi , Coutsos Matthew , Ichinose Tomoko , O'Leary Donal S.
Published: June 2021

We tested whether graded muscle metaboreflex activation (MMA) during dynamic exercise would progressively attenuate spontaneous heart rate baroreflex sensitivity (SBRS) in dogs. We measured heart rate (HR), cardiac output (CO), mean arterial and left ventricular systolic pressures (MAP, LVSP) at rest and during mild or moderate treadmill exercise before and during progressive MMA [via graded reductions of hindlimb blood flow (HLBF)]. SBRS (slopes of the linear relationships (LRs) between HR and LVSP during spontaneous sequences of ≥ 3 consecutive beats when HR changed inversely vs. pressure) decreased during mild exercise from the values at rest (−6.0 ± 1.2 vs. −3.0 ± 0.7 bpm/mmHg, P < 0.05) and these LRs were shifted upwards. Progressive MMA gradually and linearly increased MAP, CO, and HR and linearly decreased SBRS and shifted LRs upward and rightward denoting baroreflex resetting. Moderate exercise caused a substantial reduction in SBRS (−1.8 ± 0.5 bpm/mmHg, P < 0.05) and both an upward and rightward resetting. Gradual MMA again caused significant increases in MAP, CO and HR and progressive decreases in SBRS and LRs shifted to higher MAP and HR. Our results demonstrate that gradual MMA during mild and moderate dynamic exercise progressively decreases SBRS. In addition, baroreflex control of HR is progressively reset to higher blood pressure and HR in proportion to the extent of MMA. NIH HL 55473
Thyroid hormone increases beta‐catenin levels through PI3K in rat heart in vivo and in vitro
Authors: Carneiro‐Ramos Marcela Sorelli , Diniz Gabriela Placoná , Barreto‐Chaves Maria Luiza Morais , Moriscot Anselmo Sigari
Published: June 2021

Objectives: Since T3 is a potent cardiac inotropic agent and Beta‐catenin is involved in heart hypertrophy, we addressed the effects of T3 upon Beta‐catenin levels in rat heart and neonatal cardiomyocytes. Methods: Hyperthyroidism was induced by daily i.p. injections of T3 (6ug/100g/BW) from 3 to 7 days. Also, primary cultures of cardiomyocytes and fibroblasts were prepared from neonatal ventricles of Wistar rats by a collagenase/pancreatin method and then treated with T3 (10–8 M) from 5min to 3hs. Results: T3 rapidly (as soon as 3 hs after treatment) increases beta‐catenin levels in the heart. Interestingly, beta‐catenin levels are not increased by T3 in soleus muscle. A similar effect was found in cardiomyocytes, where T3 induces beta‐catenin after 30 min and in 24h beta‐catenin returned to basal levels. In cardiac fibroblasts, T3 has no effect upon beta‐catenin levels. Pharmacological inhibition of the PI3k and mTOR activities both independently suppressed the ability of T3 to increase beta‐catenin in cardiomyocytes. Pharmacological inhibition of transcription and translation also independently decreased the ability of T3 to increase beta‐catenin levels. Conclusion: These results suggest that T3 affects beta‐catenin levels throughout the PI3k/mTOR pathway in a transcriptional/translational manner and provide further insight on the cellular mechanisms involved in T3 dependent heart hypertrophy.
Weight Loss‐Associated Improvements in Vascular Endothelial Function in Overweight/Obese Humans are Related to Reductions in Abdominal Visceral Fat
Authors: Lawson Brooke R , Beske Stacy D , Southall Kara L , Benay Francoise J , Seals Douglas R , Donato Anthony J
Published: June 2021

Dietary restriction‐based weight loss (WL) may improve vascular endothelial function, but the underlying mechanisms are unclear. Endothelium‐dependent dilation (EDD) and endothelium‐independent dilation (EID) (Δ forearm blood flow [FBF] to incremental brachial artery doses of acetylcholine and sodium nitroprusside, respectively) were measured at baseline and after 12 weeks of WL (n=26/14m, 49±2y, initial BMI=29.4±0.7, mean±SE) or attention control (AC, n=14/9m, 41±3y, 30.6±0.7) in healthy overweight or obese adults (randomized design). Body weight (mean −10[range 3–15]%), total fat mass (−20[1–45]%), total abdominal fat (−27[17–50]%), abdominal subcutaneous fat (ASF, −25[2–51]%) and abdominal visceral fat (AVF, −34[2–53]%) were reduced after WL (all P<0.001), as were several conventional coronary risk factors. EDD was increased by 27% after WL (peak ΔFBF: 21.3±2.7 vs. 16.8±1.5 mL tissue−1min−1, P<0.05), whereas EID was unchanged. The only significant physiological correlates of the improvement in EDD with WL were reductions in AVF (r=−0.41, P=0.05) and the AVF:ASF ratio (r=−0.47, P<0.05) (computed tomography). No changes were observed in any of these measures after AC. Our results provide support for the idea that improvements in EDD with WL in otherwise healthy overweight or obese adults are independently related to reductions in AVF relative to ASF. NIH AG006537, AG013038, AG022241
Human epicardial adipocytes have distinct functional and structural properties as compared to subcutaneous and perirenal adipocytes
Authors: Stoll Lynn L , Chaterjee Tapan K , Denning Gerene M , Ackermann Laynez W , Flanagan Shawn W , Romig‐Martin Sara A , Dickson Eric W , Weintraub Neal L
Published: June 2021

Growing evidence suggests that adipose tissue is an important endocrine organ, and that adipocytes (Ads) from different fat depots have distinct functional properties. Epicardial (EC) fat has been shown to produce inflammatory mediators, but the functional properties of isolated EC Ads have not been determined. For our studies, we compared isolated human EC Ads with subcutaneous (SQ) and perirenal (PR) Ads from the same donors (n = 3). EC fat was more highly vascularized and had a greater density of extracellular matrix than did SQ fat. Upon differentiation, both SQ and PR Ads exhibited significant accumulation of large lipid droplets, whereas EC Ads exhibited slower lipid accumulation and smaller lipid droplets. Microarray analysis showed that EC Ads expressed higher levels of pro‐inflammatory genes, including MMP1, MMP9, IL6, IL8, MCP1, and COX2. Conversely, EC Ads expressed lower levels of leptin and of the anti‐inflammatory, cardioprotective adipokine adiponectin. EC Ads also released less adiponectin as measured by ELISA. These results suggest that EC Ads exhibit structural and functional differences as compared to SQ and PR Ads. Furthermore, the increased adiponectin expression and release by SQ Ads suggests a potential basis for the observed cardioprotective effect of gluteofemoral fat. Funding for these studies was provided by the NIH (NHLBI) and the University of Iowa Department of Emergency Medicine.
β‐arrestins mediate PAR‐2 inhibition of AMPK activity
Authors: wang ping
Published: June 2021

Adenosine monophosphate.activated protein kinase (AMPK) plays a key role in energy balance in response to energy depletion. Here we show that the pro‐inflammatory G‐protein coupled receptor, protease‐activated receptor‐2 (PAR‐2), can dually modulate AMPK activity via distinct signaling pathways. In NIH 3T3 cells, activation of PAR‐2 activated AMPK and increased phosphorylation of its substrate, Acc; both events were blocked by overexpression of β‐arrestin‐2. In mouse fat and liver, PAR‐2 only increased AMPK after genetic deletion of β‐arrestin‐2. Suppression of Ca2+/Calmodulin‐Dependent Protein Kinase Kinase‐β (CaMKK‐β) activity with STO‐609 reduced AMPK activity in both NIH3T3 cells and fat tissue from β‐arrestin 2 knockout mice. β‐arrestins associate with AMPK in both primary fat and NIH3T3 cells; this association is increased by PAR‐2 activation. These results indicate that PAR‐2 may positively regulate AMPK activity by through a Ca2+/Gαq‐CaMKKβ pathway in some cells, while inhibiting its activity in others (such as fat and liver) through β‐arrestin‐dependent inhibition of AMPK phosphorylation. These data reveal β‐arrestins can act as molecular switches in cellular energy balance in PAR‐2 actions.
Elevated glucose increases tumor necrosis factor‐α induced endothelial cell death via fibroblast growth factor‐2 release
Authors: Morss Alisa , Zhu Han , Edelman Elazer R.
Published: June 2021

Diabetic vasculopathies are accompanied by elevated glucose and tumor necrosis factor‐α (TNFα). Yet the effect of TNFα on endothelial cell (EC) function in a high glucose environment has not been measured. We examined TNFα‐induced EC death under normal and elevated glucose conditions. Upon TNFα stimulation, EC cultured in 30 mM glucose had twice the apoptosis rate of cells cultured in 5 mM glucose (p < .01). Both high glucose culture and TNFα stimulation induced EC release of fibroblast growth factor‐2 (FGF2), an angiogenic growth factor that usually protects cells from death. Surprisingly, TNFα‐induced cell death increased linearly with FGF2 exposure, with a maximal effect when FGF2 was added 18 hours prior to TNFα stimulation. This timing correlated with cell entry into S phase. Indeed, the increase in TNFα‐induced cell death in high glucose was negated with a neutralizing FGF2 antibody or by preventing cell cycle progression through S phase. These data suggest that the elevated glucose and TNFα environment in diabetes compound to detrimentally affect ECs. Cells chronically stimulated with TNFα may respond in an alternate manner to growth factors such as FGF2. This deregulation of vascular homeostasis may contribute to diabetic vascular disease.
Endothelium‐independent biphasic effects of relaxation and contraction induced by ethyl acetate extract from Morus alba L on rat aortas
Authors: Qian Ling‐bo , Cui Jie , Xia Man‐li , Bruce Iain C , Qiang Xia
Published: June 2021

The objective of the present study was to explore the underlying mechanisms of the biphasic vasoactive effect of ethyl acetate extract from Morus alba L (EMA) on the rat thoracic aortas. Isolated aortic rings were mounted on the organ bath and EMA‐induced vascular tension changes with or without endothelium were measured. Verapamil, heparin sodium, or ruthenium red was introduced to determine the underlying mechanism of vascular effects of EMA. We found that EMA (0.25–32 g/L) produced a concentration‐dependent vasorelaxation both in endothelium‐intact and ‐denuded aortas preconstricted by high K+ (60 mmol/L KCL) or 1 μmol/L phenylephrine (PE). On the contrary, EMA induced vasoconstriction in endothelium‐denuded aortas pretreated with verapamil (1 μmol/L) and preconstricted by PE, which was abolished by ruthenium red (10 μmol/L), but not by heparin sodium (50 mg/L). In endothelium‐denuded aortas, EMA reduced Ca2+ caused contraction after PE or K+ induced a stable contraction in Ca2+‐free solution. The results indicate that among the biphasic vasoactive effects of EMA, the vasorelaxation is greater than the vasoconstriction, and the vasorelaxation is independent on endothelium and at least mediated by inhibition of voltage‐ and receptor‐dependent Ca2+ channels in vascular smooth muscle cells (VSMCs), while the vasoconstriction may involve activation of ryanodine receptor in endoplasmic reticulum of VSMCs. However, the signal transduction pathway between EMA and intracellular Ca2+ transfer need to be further explored.
Epiandrosterone activates BKCa channel in bovine coronary artery smooth muscle cells
Authors: Ochi Rikuo , Gupte Rakhee S , Wolin Michael S , Gupte Sachin A
Published: June 2021

Epiandrosterone (EPI), a metabolite of testosterone precursor dehydroepiandrosterone, causes relaxation of vascular smooth muscle (VSM) associated with inhibition of glucose‐6‐phosphate dehydrogenase (G6PD), which increases cellular reducing potential by converting NADP+ to NADPH. BKCa channel is a primary K+ channels in VSM. We studied whether EPI regulates BKCa channel and whether G6PD is involved in cultured bovine coronary artery smooth muscle cells (CASMC). Whole‐cell BKCa current (IBK) was recorded in the presence of 5.4 mM [K+]o/30 mM [K+]i and 0.1 or 1 μM [Ca2+]i. IBK was predominant K+ current in CASMC. IBK increased with moderate increase of depolarization, but large depolarizations caused inactivation presenting bell‐shaped I‐V relationship. The increase of [Ca2+]i caused negative shift of maximal BKCa conductance (GBKCa). EPI (>3 μM) increased GBKCa and shifted voltage‐dependence of activation further to a negative direction; GBKCa increased by ∼50% at 10 μM and by ∼100% at 100 μM. EPI caused hyperpolarization that was reversed by TEA. Suppression of G6PD by siRNA did not affect GBKCa and EPI caused similar modulation of IBK in the G6PD KO myocytes. EPI is a novel activator of BKCa channel and the activation is independent of its inhibitory action on G6PD. EPI‐induced increase in IBK may cause relaxation of CASMC via hyperpolarization.
T‐type calcium channels regulate smooth muscle cell migration, neointimal formation, and oxygen‐induced vascular contraction in rat ductus arteriosus
Authors: Akaike Toru , Yokoyama Utako , Quan Hong , Ishikawa Yoshihiro , Minamisawa Susumu
Published: June 2021

Objective

Ca2+ influx through voltage‐dependent Ca2+ channels regulates vascular contraction and remodeling. However, the role of T‐type Ca2+ channels (TCCs) has remained unknown in the ductus arteriosus (DA).

Methods and Results 1) α1G, a TCC subtype, was significantly up‐regulated in rat neonatal DA tissues at birth and in DA smooth muscle cells (SMCs) that were exposed to oxygen. α1G was localized predominantly to the region of intimal thickening in fetal DA at term and to the central core of neonatal DA at birth. 2) α1G over expression promoted SMC migration by 164% relative to control (n=7, p<0.01). α1G‐specific siRNAs inhibited SMC migration by 60% relative to negative siRNA (n=8, p<0.01). A highly selective TCC blocker, R(−)‐efonidipine, suppressed SMC migration by 62% relative to control (n=5, p<0.01). 3) A prostaglandin E receptor EP4 agonist potently promoted physiological intimal thickening (Yokoyama et al. J Clin Invest 2006). Intimal‐media ratio of DA stimulated by EP4 was decreased by 60% in the presence of R(−)‐efonidipine (n=5, p<0.01). 4) R(−)‐efonidipine significantly attenuated oxygen‐induced vasoconstriction in a dose‐dependent manner.

Conclusion

TCC, especially α1G, regulates SMC migration, neointimal formation, and oxygen‐induced vascular contraction in rat DA.
Aging and EPC Release of Proangiogenic Factors
Authors: Kushner Erich Joseph , Hoetzer Greta L. , MacEneaney Owen J. , Greiner Jared J. , Cech Jennifer N. , Stauffer Brian L. , DeSouza Christopher A.
Published: June 2021

Circulating endothelial progenitor cells (EPCs) secrete proangiogenic factors such as vascular endothelial growth factor (VEGF), granulocyte‐colony stimulating factor (G‐CSF) interleukin (IL)‐8 and IL‐17 that aid in reendothelialization and neovascularization. VEGF and, in particular, G‐CSF also enhance vascular repair by stimulating EPC recruitment and homing to the site of damage/injury as well as providing protection from ischemia‐ and oxidative stress‐induced apoptosis. Reduced EPC‐mediated vascular repair is thought to contribute to the increased risk of atherosclerosis in older adults. We tested the hypothesis that the capacity of circulating EPCs to release proangiogenic growth factors and cytokines declines with age in healthy, sedentary adult humans. EPCs were isolated from peripheral blood samples collected from 37 healthy, sedentary men: 17 young (Y: age 25±1 yr) and 20 older (O: 61±1 yr). EPC release of VEGF, G‐CSF, IL‐8 and IL‐17 was determined (ELISA) in growth medium in response to phytohemagglutinin (PHA; 10 μg/mL) stimulation. Capacity of EPCs to release VEGF (102±12 vs 110±15 pg/mL), IL‐8 (108±10 vs 94±13 fg/mL) and IL‐17 (324±64 vs 294±102 pg/mL) was not significantly different between O vs Y. However, G‐CSF release was ~45% lower (P<0.05) in O (954±115 pg/mL) vs Y (1677±304 pg/mL). Reduced ability to release G‐CSF may contribute to deficient EPC‐mediated vascular repair with advancing age.
Cigarette smoke mediated oxidative/nitrosative stress impairs VEGF‐ and fluid shear stress‐induced endothelial function
Authors: Edirisinghe Indika , Wong Chelsea , Rahman Arshad , Phipps Richard P , Jin Zheng‐Gen , Rahman Irfan
Published: June 2021

VEGFR2, a tyrosine kinase receptor, is induced by VEGF and fluid shear stress (FSS) in endothelial cells. VEGFR2 downstream signaling is important in the regulation of normal endothelial functions such as cell migration, endothelial dependent relaxation and angiogenesis. Cigarette smoke (CS)‐induced oxidative/nitrosative stress causes modifications of the tyrosine kinase receptors and impaired cellular signaling. We hypothesized that CS‐induced reactive nitrogen/oxygen species (RNOS) impair VEGF‐ and FSS‐induced VEGFR2 kinase signaling leading to endothelial dysfunction. Human lung microvascular endothelial cells were treated with cigarette smoke extract (CSE; 0.1–0.5%) to investigate VEGF‐ or FSS‐induced VEGFR2 phosphorylation and downstream signaling that may influence endothelial function. CSE downregulated both VEGF‐ and FSS‐induced VEGFR2 phosphorylation and its downstream signaling via Akt resulting in impaired eNOS phosphorylation. CS‐derived 4‐hydroxy‐2‐nonenal and reactive nitrogen species interacted with VEGFR2 rendering VEGFR2 inactive for downstream signaling. Pretreatment of cells with the thiol antioxidant N‐acetyl‐L‐cysteine significantly attenuated the CSE‐mediated VEGF‐ and FSS‐ induced impaired VEGFR2 phosphorylation. These new findings suggest that CS‐induced RNOS impairs VEGF‐ and FSS‐induced VEGFR2 signaling leading to endothelial dysfunction in smokers. These data may have implications in the pathogenesis of pulmonary and cardiovascular diseases.

Supported by Philip Morris USA Inc. and Philip Morris International
A ROLE OF SRC‐ACTIVATED STAT‐3 IN 14, 15‐EPOXYEICOSATRIENOIC ACID‐INDUCED VEGF EXPRESSION AND ANGIOGENESIS
Authors: Cheranov Sergey Yu , Karpurapu Manjula , Wang Dong , Rao Gadiparthi N
Published: June 2021

Previously we have shown that 14,15‐epoxyeicosatrienoic acid (14,15‐EET) induces angiogenesis via PI3K‐Akt‐dependent FGF‐2 expression and mTOR‐S6K1 activation. To understand the molecular mechanisms underlying 14,15‐EET‐induced angiogenesis, here we have studied the role of STAT‐3. 14,15‐EET stimulated the tyrosine phosphorylation of STAT‐3 and its translocation from the cytoplasm to the nucleus in HDMVEC. Adenovirus‐mediated delivery of dominant negative STAT‐3 substantially inhibited 14,15‐EET‐induced HDMVEC migration, and tube formation and Matrigel plug angiogenesis. 14,15‐EET activated Src as measured by its tyrosine phosphorylation and blockade of its activation by adenovirus‐mediated expression of its dominant negative mutant significantly attenuated 14,15‐EET‐induced STAT‐3 phosphorylation in HDMVEC and the migration and tube formation of these cells and Matrigel plug angiogenesis. 14,15‐EET induced the expression of vascular endothelial cell growth factor (VEGF) in a time‐and Src‐STAT‐3‐dependent manner in HDMVEC. Transfac analysis of VEGF promoter revealed the presence of STAT‐binding elements and 14,15‐EET induced STAT‐3 binding to this promoter both in vitro and in vivo and this interaction was inhibited by suppression of Src‐STAT‐3 signaling. Neutralizing VEGF antibodies completely blocked 14,15‐EET‐induced HDMVEC migration and tube formation and Matrigel plug angiogenesis. These results show for the first time that Src‐dependent STAT‐3‐mediated VEGF expression is a major contributing factor in 14,15‐EET‐induced angiogenesis. NIH.
Proteomic Strategy for Analysis of VEGF Mediated Endothelial Cell Signaling
Authors: Parker Sarah Josepha , Greene Andrew
Published: June 2021

Vascular Endothelial Growth Factor (VEGF) is a potent and specific pro‐angiogenic cytokine, and its dysregulation has been implicated in many diseases characterized by either insufficient or excessive angiogenesis. The field of proteomics offers techniques which may greatly enhance our understanding of complex networks of protein‐protein interactions within important signaling networks such as the VEGF pathway. In the current study we examined whether a newly established technique, developed in our lab for the isolation and proteomic analysis of the TNFα signaling network, could be used to study the VEGF pathway. Recombinant rat VEGF164 was biotinylated and administered to vascular endothelial cells for 10 minutes followed by a cell permeable chemical cross‐linker (DSP). Cell lysate was then subjected to affinity chromatography with streptavidin to isolate the VEGF pathway. Western blots for the VEGF type 2 receptor and the downstream signaling proteins Akt and ERK1/2 revealed a dose‐dependent relationship for VEGF concentration, DSP concentration, and DSP administration time, with optimal values of 250ng/mL, 0.75 mM, and 10 minutes, respectively. Control samples not treated with VEGF or DSP showed minimal expression. These data suggest that our technique is successful in isolating the VEGF pathway, and can be utilized for identification of proteins and post‐translational modifications via LC‐MS/MS.
Methamphetamine‐induced oxidative‐stress modifies contractile and mitochondrial proteins in the heart
Authors: Lord Kevin C , Shenouda Sylvia K , McIlwain Elizabeth , Pollman Megan , Lucchesi Pamela A. , Varner Kurt J.
Published: June 2021

We reported that binge administration of methamphetamine (METH) produces eccentric left ventricular (LV) dilation, systolic and diastolic dysfunction. Although the mechanisms underlying these deficits are unknown, our data using the antioxidant tempol, suggests that oxidative stress plays a significant role. We hypothesized that the increase in oxidative stress produces LV dysfunction via the posttranslational modification of myocardial proteins. Male Sprague‐Dawley rats were treated with METH or saline (2×d for 4 d), followed by a 10 day drug‐free period (“binge”). One day after the fourth binge, eccentric dilation was observed in METH‐treated rats. Proteomic analysis showed that compared to saline, METH‐treated rats had increased nitration and oxidation of contractile (actin, alpha‐beta crystalline, myosin light chain) and mitochondrial (cytochrome C reductase, F1 ATP synthase, NADH dehydrogenase) proteins. Electrically stimulated (1 Hz) adult LV myocytes from METH‐treated rats exhibited decreased contractility and impaired relaxation compared to control. Post‐stimulus [Ca2+]i was decreased while its return to baseline was unaffected. In conclusion, the LV dysfunction produced by METH may be due to the redox modification of contractile and/or mitochondrial proteins but not calcium handling proteins. Support: AHA 655769, NIH P20‐RR018766