bluuebunny/crossref_metadata_2025 huggingface dataset:
The Efficacy of Electrical Baroreflex Activation Therapy is Independent of Peripheral Chemoreceptor Modulation
Authors: Heusser Karsten , Thöne Arvo , Lipp Axel , Menne Jan , Beige Joachim , Reuter Hannes , Hoffmann Fabian , Halbach Marcel , Eckert Siegfried , Wallbach Manuel , Koziolek Michael , Haarmann Helge , Joyner Michael , Paton Julian F. R. , Diedrich André , Haller Hermann , Jordan Jens , Tank Jens
Published: June 2021

Introduction

Baroreflex activation through electrical carotid sinus stimulation has been developed for the treatment of patients with arterial hypertension not sufficiently responding to pharmacological therapy. Previous studies suggested that peripheral chemoreflex afferents located in proximity to carotid baroreceptors are tonically active in hypertensive patients and may inhibit baroreflex responses. Therefore, we hypothesized that peripheral chemoreflex activation attenuates the efficacy of electrical carotid sinus stimulation.

Methods

We screened 35 patients with an implanted electrical carotid sinus stimulator. Of those, 11 patients exhibited a consistent acute depressor response and were included in the study (7 men/4 women, age: 67±8 years, BMI: 31.6±5.2 kg/m2, 6±2 antihypertensive drug classes). We assessed responses to electrical baroreflex stimulation during normoxia, isocapnic hypoxia (SpO2: 79.0±1.5%), and hyperoxia (40% end‐tidal O2 fraction) by recording ECG, blood pressure (SBP), ventilation, SpO2, end‐tidal CO2 and O2 fractions, and muscle sympathetic nerve activity (MSNA).

Results

During normoxia, baroreflex activation reduced SBP from 164±27 to 151±25 mmHg (means±SD, p<0.001), HR from 64±13 to 61±13 bpm (p=0.002), and MSNA from 42±12 to 36±12 bursts/min (p=0.004). Hypoxia increased SBP 8±12 mmHg (p=0.057), HR 10±6 bpm (p<0.001), MSNA 7±7 bursts/min (p=0.031), and ventilation 10±7 l/min (p=0. 002). However, responses to electrical carotid sinus stimulation did not differ between hypoxic and hyperoxic conditions; SBP: −15±7 vs −14±8 mmHg (p=0.938), HR: −2±3 vs −2±2 bpm (p=0.701), and MSNA: −6±4 vs −4±3 bursts/min (p=0.531).

Conclusion

The main finding of our study is that moderate peripheral chemoreflex activation does not attenuate acute responses to electrical baroreflex activation therapy (BAT) in patients with resistant hypertension. These patients provide insight in human baroreflex physiology and baroreflex‐chemoreflex interactions that could not be gained otherwise.

Support or Funding Information

Financial support by Boston Scientific Corporation (St. Paul, MN, U.S.A.)

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
mTORC1 in leptin receptor‐containing neurons mediates an obesity‐induced increase in sympathetic tone and blood pressure
Authors: Bell Balyssa , Morgan Donald , Rahmouni Kamal
Published: June 2021

The adipocyte‐derived hormone leptin acts via the sympathetic nervous system to influence both metabolic homeostasis and blood pressure. Leptin has also been implicated as an important mediator of obesity‐induced elevation in sympathetic nerve activity (SNA) and blood pressure, but the underlying mechanisms remain poorly understood. Here, we investigated the contribution of mechanistic target of rapamycin complex 1 (mTORC1) signaling in leptin receptor (LepRb)‐containing neurons to metabolic, sympathetic and hemodynamic dysregulation associated with obesity. For this, we generated a genetically modified mouse model (LepRbCre/Raptorfl/fl) that lacks a critical subunit of the mTORC1 complex selectively in LepRb expressing cells. Surprisingly, loss of mTORC1 in LepRb‐containing cells had no effect on body weight, fat accumulation, or glucose handling. Furthermore, LepRbCre/Raptorfl/fl mice fed high‐fat or high‐fat/high‐sucrose diet developed obesity to a similar extent as control littermates, indicating that mTORC1 in LepRb expressing cells is dispensable for metabolic homeostasis. On the other hand, while conscious basal renal SNA was significantly elevated in control mice fed high‐fat/high‐sucrose diet relative to control animals on standard diet, this increase in sympathetic tone to the kidneys was attenuated in LepRbCre/Raptorfl/fl mice. Consistent with an impaired cardiovascular autonomic response to diet‐induced obesity in these animals, ganglionic blockade with hexamethonium bromide caused a trend towards a more pronounced decrease in blood pressure in high‐fat/high‐sucrose diet fed control animals as compared to LepRbCre/Raptorfl/fl mice. Interestingly, renal SNA was decreased in response to hexamethonium to a similar extent in all groups, regardless of diet or genotype, indicating an important role for extra‐renal and/or parasympathetic changes in autonomic nerve activity during diet‐induced obesity. High‐fat/high‐sucrose diet treatment also increased blood pressure and decreased cardiac parasympathetic tone in control mice, as determined by radiotelemetry and accompanying spectral analysis, and ICV rapamycin infusion resulted in a trend towards a partial reversal of these effects. Together, these findings indicate that mTORC1 signaling in LepRb‐containing cells is required for obesity‐induced sympathetic nerve activation and hypertension. This signaling pathway may represent an important mechanism for uncoupling obesity from its associated cardiovascular disorders.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Incubation of NTS Neurons in High Glucose Decreases the Sensitivity to a Low Glucose Challenge: Role of KATP Channels
Authors: De Bernardis Murat Cahuê , Leão Ricardo Mauricio
Published: June 2021

The brainstem nucleus of the tractus solitarius (NTS) is an integrative center for the counterregulatory responses to hypoglycemia, and recent evidences have showed that NTS neurons can directly sense extracellular glucose fluctuations via mechanisms that rely on glucose metabolism. The ATP‐sensitive potassium (KATP) channels play a key role in linking metabolic status and electrical excitability in glucose‐sensing neurons, and KATP channels are expressed in NTS neurons. Therefore, this work aimed to investigate the effect of a low external glucose (0.5 mM) on the membrane properties of NTS neurons of rats, and its interaction with KATP channels, by whole‐cell patch‐clamp. We observed that low glucose induces a voltage‐dependent depolarization in most NTS neurons, i.e., the more negative the resting membrane potential (RMP) of neurons, the higher membrane potential amplitude response. KATP channels are opened at rest in NTS neurons maintained in 5 mM extracellular glucose, and contribute to the hyperpolarized RMP of neurons. Blockage of KATP channels with tolbutamide strongly depolarizes neurons and occludes the effect of low glucose, thus acting as modulators of low‐glucose sensing in NTS neurons. Membrane hyperpolarization after blockage of KATP channels restores the depolarizing effect of low glucose. Additionally, the incubation of NTS neurons in high‐glucose (10 mM) aCSF prior to electrophysiological recordings leads to more depolarized RMP, what contributes to increase the number of neurons unresponsive to a low‐glucose challenge. Again, membrane hyperpolarization restores the depolarization induced by low glucose, however, tolbutamide application did not produced the pronounced membrane depolarization in comparison to NTS neurons incubated in 5 mM glucose aCSF, confirming that KATP channels are closed in a high‐glucose environment. We conclude that (1) low‐glucose sensing in NTS neurons is a voltage‐dependent mechanism; (2) KATP channels influence the RMP of neurons, thus modulating the sensitivity of these neurons to low glucose; (3) incubation of NTS neurons in high‐glucose decrease the number of responsive neurons to low glucose, possibly by depolarization via inhibition of KATP channels following increased amounts of high glucose‐derived ATP levels; (4) this effect could be a permissive mechanism for the decreased brain response to hypoglycemia in individuals that experience recurrent episodes of hypoglycemia, such as insulin‐treated diabetic patients, and; (5) depolarization induced by low glucose might represent a form of homeostatic regulation of the RMP in order to avoid an excessive hyperpolarization by unblocking KATP channels under a hypoglycemia episode.

Support or Funding Information

CAPES, CNPq, FAEPA, and FAPESP.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
PLASMA ERYTHROPOIETIN CONCENTRATION DETERMINE THE CAROTID BODY CHEMOSENSITIVITY TO HYPOXIA AND HYPERCAPNIA IN RATS
Authors: LAOUAFA Sofien , TAM Rose , BAIRAM Aida , JOSEPH Vincent , SOLIZ Jorge
Published: June 2021

We tested the hypothesis that Erythropoietin (Epo) have an impact in the modulation of carotid body (CB) chemoreceptors in response to hypoxia and hypercapnia. To study this subject, we used isolated and perfused ex vivo CB preparations from adult male Sprague Dawley rats. Prior evaluation of the carotid sinus nerve activity (CSNA ‐ throughout a suction glass electrode encircling and sealing the junction of the carotid body and the carotid sinus nerve), preparations were incubated for 1h with (or without) Epo at different concentrations. Then CBs were exposed to hypoxic and hypercapnic conditions. Normoxic baseline activity was not affected by any tested Epo concentration. However, under hypoxia and hypercapnia, Epo doses lower than 0.5U/ml increased the CSNA (by almost 40%), Epo doses higher than 0.5U/ml gradually decreased the CSNA in hypoxic and hypercapnic condition. Complete inhibition of CSNA was reached when preparations were incubated with 2U/ml of Epo concentration. Keeping in mind that nitric oxide (NO) in CB is an inhibitory messenger and that Epo in combination with low oxygen tension increase the endothelial capacity to produce NO, preparations were incubated at the same time with Epo (at the inhibitory concentration of 1 U/ml) and NO inhibitors, 400 μM L‐NAME (Nitric synthase inhibitor) or 100 μM 7NI (specific neuronal Nitric oxide synthase inhibitor). Our results showed that inhibition of NO (with L‐NAME and 7NI) fully restored the hypoxic CSNA. Similar results were found by exposing CB preparations to hypercapnic conditions. Accordingly, to these findings, immunohistochemistry studies showed a dense staining of Epo receptors (EpoR) in the carotid bodies, apparently localized within islets of chemosensitive cells. In summary, our results strongly suggest that the plasma Epo concentration determines the CB chemo‐response to hypoxic and hypercapnic conditions. These novel findings are relevant to better understand respiratory disorders, including those occurring at high altitude.

Support or Funding Information

CIHR, Région Rhône Alpes and consulat de France in Québec

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Angiotensin 1–7 Action in the Lateral Preoptic Area is Involved in Urinary Bladder Regulation in Female Wistar Rats.
Authors: Lamy Gustavo Bertollini , do Vale Barbara , de Almeida Roberto Lopes , de Brito Antonio Bruno , Venancio Daniel Paulino , Sato Monica Akemi
Published: June 2021

Background

Chemical lesions of the lateral preoptic area (LPA) enhance water intake induced by subcutaneous injection of hypertonic saline in rats. On the other hand, the LPA section abolishes the increase in intravesical pressure (IP) induced by olfactory tubercle stimulation in dogs. Immunohistochemical labeling has demonstrated the presence of Mas receptors for Angiotensin‐(1–7) in LPA. It is not known whether neurons with Mas receptors in LPA are involved in urinary bladder regulation.

Aim

We investigated the effects of activation or blockade of Mas receptors for angiotensin‐(1–7) in LPA on intravesical pressure in anesthetized female rats.

Materials and methods

Female Wistar rats (~240 g, N=6) underwent to a stereotaxic surgery for implantation of stainless steel guide cannulas into the LPA under ketamine and xylazin anesthesia. After 7 days, the animals were anesthetized and maintained with 2% isoflurane in 100% O2 and submitted to cannulation of the femoral artery and vein, placement of a miniaturized Doppler flow probe around the left renal artery to measure the renal blood flow and cannulation of the urinary bladder for IP measurements. After baseline IP and cardiovascular parameters recordings for 15 min, angiotensin‐(1–7) (5 nmol/ uL) or saline (1 uL) or A‐779 (Mas receptor antagonist, 50 nmol/uL) was injected into the LPA and the variables were measured for additional 60 min.

Results

Unilateral injection of angiotensin‐(1–7) into LPA evoked a significant increase in IP (187.5±37.2%) compared to saline (−2.1±1.9%). Unilateral injection of A‐779 into LPA decreased the IP (−15.9±2.8%) in comparison to saline (2.0±1.1%). Interestingly, the decrease in IP was enhanced after bilateral injection of A‐779 into LPA (−27.3±3.4%) compared to the unilateral injection of this drug and also in comparison to saline (−2.9±1.6%) bilaterally into LPA. No significant changes in cardiovascular parameters after angiotensin‐(1–7) or saline or A‐779 in APL were observed.

Conclusion

The data suggest that LPA is an important part of the circuit that regulates the urinary bladder activity mediated by angiotensin‐(1–7).

Support or Funding Information

Financial support: FAPESP and NEPAS‐FMABC

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Cardiodynamic Associations With Mental Health And Resilience In Undergraduate Students
Authors: Knetsch Rachel , Klassen Stephen A. , Shoemaker J. Kevin
Published: June 2021

The 2016 National College Health Assessment (NCHA) indicates a majority of Canadian students reported feeling overwhelmed, stressed, and anxious during their undergraduate studies, which lead to poorer academic performance. Heart rate variability (HRV), the variation in time between consecutive heart beats, is indicative of the inherent flexibility of a healthy autonomic nervous system. While autonomic indices, in the form of HRV, have been used to describe chronic physiological stress, the role of HRV as a physiological index of mental health remains unclear. Furthermore, HRV monitoring may provide a quantitative means for interpreting the gradation of stress and anxiety experienced by undergraduate students. The objective of this study was to analyze the relationship between cardiac autonomic control and mental health scores in undergraduate students. Seventy‐seven healthy undergraduate students (18–24 years of age, 17 males; Western University, Canada) wore a Firstbeat Bodyguard® device for a 24‐hour period while continuing with day‐to‐day activities. Sleep R‐R interval data were isolated, and the root mean square of successive differences (RMSSD; Firstbeat® software) was calculated. Students also completed the brief resilience scale (BRS), generalized anxiety disorder 7‐item scale (GAD‐7), and the mental health inventory (MHI) questionnaires. Regression analysis established the predictive relationship between RMSSD and the psychological survey scores for this sample. The RMSSD index correlated positively with BRS (r=0.30, p<0.01). The RMSSD index correlated negatively with GAD‐7 scores (r=−0.27, p<0.05). The RMSSD index did not correlate with MHI scores. These data suggest that higher HRV may indicate greater psychological resilience, and lower anxiety amongst undergraduate students.

Support or Funding Information

Western University Interdisciplinary Initiative Program

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sympathoexcitatory role for neurons projecting from the mesencephalic locomotor region to the rostral ventrolateral medulla in rats
Authors: Koba Satoshi , Kumada Nao , Hanai Eri , Kataoka Naoya , Nakamura Kazuhiro , Watanabe Tatsuo
Published: June 2021

C1 neurons in the rostral ventrolateral medulla (RVLM) are reportedly excited by voluntary exercise. The present study aimed to explore neural pathway(s) upstream to the RVLM that can play a role in sympathetic adjustments to exercise. First, via neuronal tracing experiments, we found that rat mesencephalic locomotor region (MLR), in which cholinergic neurons are abundantly distributed, sends direct projections to the RVLM (MLR‐RVLM neurons) since the MLR contained a number of neuronal cells immunoreactive to cholera toxin subunit B (CTb) that had been injected into the RVLM in advance (n = 8). It is noted that very few neurons immunoreactive to choline acetyltransferase in the MLR were labeled with CTb (n = 3), suggesting that the MLR‐RVLM neurons are not cholinergic. Next, we found that optogenetic stimulation of MLR‐RVLM neurons causes sympathoexcitation in rats. An AAV vector that encodes the channelrhodopsin variant, ChIEF‐tdTomato was bilaterally microinjected into the MLR (n = 7). More than 3 weeks later, bilateral photostimulation (473 nm wavelength, 10 mW, 40 Hz) provided to the RVLM of the anesthetized rats significantly (P < 0.05) elevated blood pressure. In another set of rats (n = 3), a retrograde AAV vector that encodes the channelrhodopsin‐GFP was bilaterally microinjected to the RVLM. In these rats, bilateral photostimulation of the MLR, in which a number of GFP‐labeled cell bodies were confirmed, significantly increased renal sympathetic nerve activity and blood pressure. Finally, confocal imaging revealed that MLR‐derived, tdTomato‐labeled axons containing VGLUT2 were closely associated with tyrosine hydroxylase‐positive neurons in the RVLM, suggesting that MLR‐RVLM glutamatergic neurons form synaptic contacts with RVLM C1 neurons. Based on these observations, we propose that excitation of MLR‐RVLM glutamatergic neurons contribute to sympathetic adjustments to exercise via stimulation of RVLM C1 neurons.

Support or Funding Information

This study was supported by JSPS KAKENHI 15H05367 (SK) & 16K15190 (SK); 16H05128 & 15H05932 (KN).

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Effects of Contralateral Forearm Somatosensory Stimulation on Heart Rate Responses to Isometric Hand Grip Exercise
Authors: Smith Sydney Olivia , Woehrle Emilie , Klassen Stephen Alexander , Jacobs Kaitlyn Grace , Knetsch Rachel , Shoemaker J. Kevin
Published: June 2021

Background

Vagal withdrawal forms the dominant mechanism determining the rapid heart rate (HR) response at the onset of moderate intensity isometric handgrip (IHG) exercise. Previous evidence suggested that the addition of submotor somatosensory stimulation (STIM) can elevate vagal cardiac function in some individuals. This study tested the hypothesis that STIM can interfere with the vagal withdrawal and HR responses at the exercise onset.

Methods

Young healthy individuals (n=7, ages 24 ± 1.2 years) were recruited. STIM was provided by transcutaneous electrical nerve stimulation (TENS; 100 Hz, 50 μs) on the medial forearm through anesthetized skin. A 3‐lead ECG provided R‐R interval data. Participants performed 2–3 trials of IHG at 35–40% maximal voluntary contraction, each lasting 20 seconds and separated by one minute of rest. These were performed both with and without STIM and baseline cardiovagal influence was modified by repeating the tests in seated and supine positions using a varied order of STIM delivery.

Results

IHG elicited increased HR in each posture (supine: baseline=64 ± 9 bpm, IHG=73 ± 7 bpm; p<0.05; seated: baseline=66 ± 6 bpm, IHG=78 ± 8 bpm, p<0.05). In the seated position, STIM reduced the maximum HR response to IHG, compared to no STIM, in five out of seven participants resulting in an overall modest effect (no STIM: 19 ± 10 bpm; STIM: 15 ± 8 bpm; p<0.05; d=0.44). In the supine position, however, the effect of STIM to reduce the HR response was observed in only three out of seven participants. Thus, there was no significant difference between treatments (no STIM: 15 ± 7 bpm; STIM: 16 ± 9 bpm; p>0.05; d=0.12).

Conclusion

These data suggests that the HR response to exercise in young healthy adults can be modulated with submotor somatosensory nerve stimulation but that this effect is most apparent in the seated position.

Support or Funding Information

Supported by Natural Sciences and Engineering Research Council of Canada

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Loss of Hypoxia Inducible Factor‐1α Increases Right Ventricular Hypertrophy in Chronic Hypoxia‐Induced Pulmonary Hypertension
Authors: Smith Kimberly A. , Waypa Gregory B. , Dudley V. Joseph , Schumacker Paul T.
Published: June 2021

Pulmonary hypertension (PH) is a risk factor for right ventricular (RV) hypertrophy and right heart failure in patients with congenital heart disease, chronic obstructive pulmonary disease, interstitial lung diseases, and obstructive sleep apnea. Chronic alveolar hypoxia (CH) in these diseases promotes sustained pulmonary vasoconstriction and pulmonary artery (PA) remodeling resulting in the development of PH. Patient outcome, however, is often determined by the response of the RV to increased afterload caused by increased PA resistance. Little is known about the cellular and molecular mechanisms involved in RV hypertrophy associated with PH, which begins as compensated hypertrophy but can progress to dilated, decompensated RV failure, and death. Recently, we have shown that loss of hypoxia inducible factor 1 alpha (HIF‐1α) in PA smooth muscle cell (PASMC) attenuates PA remodeling and the increase in RV systolic pressure (RVSP) induced by CH but fails to attenuate RV remodeling. This suggests that CH directly regulates RV remodeling independently from PH and increased RVSP. Therefore, we aimed to determine the role of HIF‐1α in RV remodeling in CH‐induced PH. Genetic deletion of HIF‐1α from smooth muscle (SM) was achieved by breeding SM‐heavy myosin chain‐Cre expressing mice (SMC) with HIF‐1αflox/flox mice to generate SMC‐HIF‐1αflox/flox mice. Genetic deletion of HIF‐1α from cardiomyocytes was achieved by breeding cardiac‐specific alpha myosin‐heavy chain‐Cre expressing mice (Myh6Cre) with HIF‐1αflox/flox mice to generate Myh6Cre‐HIF‐1αflox/flox mice. A double SM and cardiomyocyte knockout was also generated by crossing SMC‐HIF‐1αflox/flox with Myh6Cre‐HIF‐1αflox/flox mice to generate SMC‐Myh6Cre‐HIF‐1αflox/flox mice. Tamoxifen was administered i.p. to activate Cre‐mediated excision of the HIF‐1α gene in targeted cells of adult mice. Wildtype, SMC‐, Myh6Cre‐ and SMC‐Myh6Cre‐HIF‐1α‐depleted mice were then housed under normoxia or CH (10% O2) for four weeks. CH increased RVSP and RV remodeling in wildtype mice. Loss of HIF‐1α in SMC‐HIF‐1α or SMC‐Myh6Cre‐HIF‐1α attenuated the CH‐induced increase in RVSP, but did not alter RV remodeling. Interestingly, the deletion of HIF‐1α from cardiomyocytes (Myh6Cre‐HIF‐1α) increased RV hypertrophy compared to wildtype mice in CH while having no effect on RVSP. These data suggest that HIF‐1α regulates RV remodeling and that loss of HIF‐α in cardiomyocytes results in unregulated cardiac remodeling during CH. Understanding the role of HIF‐1α in RV remodeling in PH may provide therapeutic targets for the development of improved treatment strategies for patients with PH.

Support or Funding Information

Supported by NIH Grants HL35440 and HL122062 (PTS) and Parker B. Francis Fellowship (KAS)

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sildenafil Abolishes Pulmonary Hypertension Induced by Left Heart Pressure Overload in Rats
Authors: Chovanec Milan , Al‐Hiti Hikmet , Kaftanova Barbora , Durisova Jana , Hampl Vaclav , Herget Jan
Published: June 2021

Pulmonary hypertension (PH) induced by pressure overload of the left heart has recently attracted increasing attention in clinical practice. Unfortunately, no specific treatment of PH is approved for this group of patients. We previously described a simple rodent model of this condition. In this study, we used it to test a hypothesis that sildenafil can be beneficial in this type of PH. Left heart pressure overload was induced in adult male Wistar rats by partial intravascular obstruction of the ascending aorta. Three weeks later, sildenafil was given (25mg/kg, oesophageal gavage once a day) for the next 2 weeks (group HFS, n=7). The group HFS was compared to the group of rats with left heart pressure overload for 3 weeks with no additional use of sildenafil (group HF, n=9) and with controls (group C, n=6). Mean pulmonary arterial pressure was significantly lower in the group HFS compared to the group HF (12.9±0.8 mmHg vs. 20.3±1.0 mmHg, p<0.0001, respectively) but was not different from the group C (10.7±1.1 mmHg). Weight of the right ventricle relative to the body weight (RV/BW ratio) as well as right ventricle weight relative to the left ventricle plus septum (RV/LV+S ratio) were significantly lower in the group HFS compared to the group HF (RV/BW ratio: 4.1±0.3.10−4 vs. 6.3±0.8.10−4; p<0.01, respectively and RV/LV+S ratio: 0.23±0.02 vs. 0.41 ±0.07; p<0.05, respectively) but they were not different in the group HFS compared to the group C in both parameters. The amount of expired nitric oxide, measured by chemiluminescent method on day 10 of the left heart pressure overload, was significantly increased in the group HF compared to the group C (343.0±30.5 pg/min/100g vs. 239.8±18.2 pg/min/100g; p<0.05, respectively). Sildenafil abolishes the developed pulmonary hypertension caused by the left heart pressure overload in the rats.

Support or Funding Information

Supported by grants: GAUK 210216 and GACR 17‐11223S

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Effects on Breathing and the CO2 Chemoreflex of 5‐HT and NK‐1 Receptor Antagonists in the Retrotrapezoid Nucleus (RTN)
Authors: Dillard Matt L. , Mouradian Gary , Hodges Matthew R.
Published: June 2021

Serotonin (5‐HT) and Substance P, typically increase the excitability of neurons within the neural network controlling breathing through G protein‐coupled receptors. These neuromodulators also stimulate pH/CO2 sensitive Phox2b‐expressing (Phox2b+) neurons in the retrotrapezoid nucleus (RTN), but their role in supporting the ventilatory CO2 chemoreflex within the RTN has not been tested in vivo. We hypothesize that unilateral antagonism in the RTN of 5‐HT and/or NK‐1 receptors will attenuate the ventilatory CO2 chemoreflex. To test this hypothesis, 8 week old male Sprague Dawley rats were chronically implanted with guide cannula unilaterally using stereotaxic coordinates previously published (Dias et al., 2008). After 7 or more days of recovery, microdialysis probes were inserted into the guide cannula for dialysis of mCSF alone followed by mCSF mixed with individual or a cocktail of antagonists to 5‐HT7 receptors (SB 269970 (100 μM)), 5‐HT2A receptors (MDL 11,939 (20 μM)) and/or NK‐1 receptors (SR 140333 (40 μM)) while measuring breathing in room air (35 min) and during a 7% CO2 challenge (10 min) before and during drug dialysis. We found that SB 269970 consistently reduced hypercapnic breathing frequency (−9 ± 2%, n=3) compared to mCSF alone, and had mixed effects on eupneic breathing and hypercapnic tidal volume. MDL‐11939 consistently reduced eupneic breathing frequency (−7 ± 0.4%, n=3) and hypercapnic tidal volume (−17 ± 0.8%, n=3) compared to mCSF alone, but had mixed effects on eupneic tidal volume and hypercapnic breathing frequency. In addition, a cocktail of all antagonists consistently increased eupneic breathing frequency (+14%, n=2) and decreased hypercapnic breathing frequency (−7 ± 0.4%, n=2) compared to mCSF alone. These preliminary data suggest 5‐HT and Substance P within the RTN may modulate breathing at rest and during hypercapnic conditions in vivo.

Support or Funding Information

This work was supported by NIH HL122358.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Dropping the base: Characterizing the hypercarbia recovery strategies following extreme hypercapnia in the highly CO2 tolerant hagfish (Eptatretus stoutii)
Authors: Clifford Alexander Michael , Weinrauch Alyssa M. , Goss Greg G.
Published: June 2021

As scavengers that feed on decaying carrion (e.g. fish, large marine mammals), hagfish (Eptatretus stoutii) can be subjected to noxious environmental stresses such as high ammonia, anoxia and hypercapnia. While the physiological impacts and the hagfishes' tolerance of these stressors have been well characterized, little data exists on the mechanisms and strategies for recovery from these stressors that would be mandatory in the natural environment. Indeed, hagfish are capable of tolerating extreme hypercapnia (>30 Torr; 72h) by building up plasma [HCO3−] over 24 – 48 h of exposure, attaining the highest plasma [HCO3−] levels ever observed in any organism (~70 mmol HCO3− L−1). The goal of this study was to characterize the hypercarbia recovery strategies of the highly CO2 tolerant following hypercapnia exposure. In a series of experiments, hagfish were exposed to hypercapnia (4% CO2) for 48 h to induce hypercarbia before being allowed to recover in normocapnic seawater. During this recovery period, measurements of blood acid/base status, plasma [Cl−] and net H+/HCO3− flux were made to elucidate the recovery strategies of the hagfish. Upon reintroduction into nonromantic conditions, hagfish rapidly (<8h) offloaded the compensatory base load (65.8 ± 2.1 mmol HCO3− L−1) while sustaining an incredible blood alkalosis of ~0.8 pH units compared to post‐exposure conditions, to a blood pH 8.67 ± 0.03 within 4h of recovery. While increases in both whole‐animal HCO3− excretion and glomerular filtration were observed throughout recovery (2–8 h), neither can fully account for the observed rates of whole‐animal HCO3− loss, which peaked at ~3.5 mmol kg−1 h−1. Inhibition of carbonic anhydrase using acetazolamide revealed that restoration of plasma [HCO3−] from hypercapnia‐induced hypercarbia is likely facilitated in a dualistic manner, initially relying on both carbonic anhydrase mediated CO2 offloading and Cl−/HCO3− exchange processes, both of which are likely either upregulated or further activated as recovery progresses.

Support or Funding Information

NSERC (GGG: 203736)

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Selective Depletion of Astrocytes Derived From a Phox2b‐Progenitor Domain Reduces Hypoxia Ventilatory Response in Conscious Mice
Authors: Silva Talita M. , Czeisler Catherine , Takakura Ana C. , Otero José J. , Moreira Thiago S.
Published: June 2021

The peripheral chemoreceptors stimulate the respiratory pattern generator directly and indirectly by activating retrotrapezoid nucleus (RTN) via a neuronal projection from the nucleus of the solitary tract. The RTN neurons express the transcription factor Phox2b. In addition to neurons, astrocytes from ventral medullary surface appear to contribute to respiratory drive and have a developmental connection with RTN neurons, the aim of this study is determine the extent to which selective ablation of PHOX2B‐derived astrocytes affect ventilation during development. We interbred ALDH1L1loxp‐GFP‐STOP‐loxp‐DTA mice to PHOX2Bcre mice. Breathing variables [tidal volume (VT), respiratory frequency (fR), and minute ventilation (VE)] were measured by whole body unrestrained plethysmography in conscious adult mice. PHOX2B‐derived astrocytes ablation (genotype PHOX2Bcre, ALDH1L1loxp‐GFP‐STOP‐loxp‐DTA) reduces hypoxia (8% O2)‐induced increased in VE (3139.22 ± 250.76, vs. control [genotype ALDH1L1loxp‐GFP‐STOP‐loxp‐DTA] 4194.7 ± 235.16 μl/min/g; p = 0.021; n=6) and VT (13.93 ± 0.6, vs. control 16.53 ± 0.7 μl/g; p = 0.0019; n=6). Our results showed that ablation of PHOX2B‐derived astrocytes produced severely impaired O2 chemosensory response, indicating that these cells may be part of a specialized neural circuitry involved breathing activation.

Support or Funding Information

FAPESP and NIH

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Wall Shear Stress and Sphingosine‐1‐Phosphate Synergistically Activate Ca2+ Signaling via Piezo1 to Mediate Angiogenesis
Authors: Kang Hojin , Mittal Manish , Zhong Ming , Komarova Yulia , Mehta Dolly , Malik Asrar B.
Published: June 2021

The sensing of wall shear stress (WSS) by endothelial cells (ECs) mediates sprouting angiogenesis; however, the underlying signaling mechanisms remain unclear. Here we investigated the synergism between WSS and the angiogenic mediator Sphingosine‐1‐phosphate (S1P) in activation of the mechanosensitive ion channel protein Piezo1, expressed in ECs. Studies were made in EC monolayers exposed to WSS of 5 dyne/cm2, the level approximating venular WSS, in which sprouting angiogenesis in 3D collagen matrix was assessed with and without challenge with S1P. WSS or S1P alone induced little angiogenesis; however, WSS combined with S1P resulted in robust angiogenesis suggesting that efficient angiogenesis requires both mechanical and humoral stimuli. These angiogenic responses were inhibited by suppression of Piezo1 expression in both human and murine endothelial monolayers as well as in vivo models. Specifically, studies in mice in which Piezo1 was conditionally deleted in ECs (Piezo1iEC‐KO) demonstrated the requisite role of S1P‐dependent activation of Piezo1 in mediating angiogenesis in vivo. S1P functioned by activating the Ca2+ gating function of Piezo1, which in turn signaled the activation of calpain and the metalloproteinases, matrix metalloproteinase‐2 (MMP2) and membrane type 1‐matrix metalloproteinase (MT1‐MMP). S1P synergizes with WSS to induce Ca2+ influx via Piezo1 and thereby activate activities of MT1‐MMP, and mediate sprouting angiogenesis.

Support or Funding Information

This work is supported by T32 HL07829, AHA 17SDG33700146 grants to HK and HL45638 grant to YK and ABM.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sex‐Specific Aspects in Cardiac Transplantation Evaluated by Left Ventricular Size in Male and Female Recipients
Authors: Kerkhof Peter L. , Parry Gareth
Published: June 2021

BACKGROUND

Both ejection fraction (EF) and end‐systolic volume (ESV) have been advanced as significant determinants of survival in patients with myocardial ischemia or heart failure. In heart transplant (HTX) patients sex‐based mismatch is recognized as an important factor for outcome. Also, it is well established that in the healthy adult population, as well as in various cardiac diseases, the left ventricular (LV) volume is significantly smaller in females (F) compared to males (M), even after indexation for body surface area.

AIM

On the basis of the reported observations we investigated the impact of the various donor/recipient combinations on both ESV and EF, as well as on their interrelationship.

METHODS

In previous studies we have demonstrated that EF is nonlinearly related to ESV, yielding identical regression curves for men and women based on the robust expression EF = 100 [1 + C1{ESV/(C2‐ESV)}], where C1 and C2 are population based constants. In 94 HTX patients we studied LV volume obtained by CT, where images were processed on a Siemens Syngo Via workstation.

RESULTS

Distribution of the various sex‐related combinations was: M to M (51), M to F (12), F to M (13), and F to F (18). We calculated ESV vs EDV regression lines to estimate C1 and C2.

For M to M the C1 and C2 are 0.68 and −53.14, respectively, with R2=0.45

For M to F the C1 and C2 are 0.83 and −64.86, respectively, with R2=0.84.

Linearized EF versus ESV yields significant (P for all < 0.001) inverse relationships which for the four study groups are fairly similar. Despite the fact that 40% of the hearts were from male donors, ESV was found to be smaller (P=0.0019) in all female recipients, similar as observed in healthy women when compared to men. In contrast and against expectation, EF was not higher in female compared to male recipients, suggesting that an extra component beyond EF needs to be identified which may have better power to discriminate.

CONCLUSIONS

Sex‐associated LV volumetric characteristics known from previous studies, also appear to be reflected in the recipients regardless of donor sex, suggesting that the LV size of the new heart tends to adapt to the sex of the recipient. We found that EF does not discriminate between the four groups, in contrast to ESV which is significantly smaller in female recipients, irrespective of the sex of the donor. Longitudinal studies may provide further clarification about the underlying mechanism(s) which are responsible for the sex‐specific adaptation in HTX recipients.

Support or Funding Information

none
Hydrogen sulfide improves endothelial dysfunction through inhibition of the vicious circle of NLRP3 and oxidative stress in spontaneously hypertensive rats
Authors: Wu Yuming , Li Jiabao
Published: June 2021

Aims

The aim of this study is to elucidate whether the inhibition of inflammasome and oxidative stress mediated the ameliorative effect of hydrogen sulfide (H2S) on endothelial dysfunction in hypertension.

Methods

Spontaneously hypertensive rats (SHR) and normotensive Wistar kyoto rats (WKY) were injected with 100 μM NaSH intraperitoneally daily for 16 weeks. Systolic blood pressure (SBP) and plasma MDA and IL‐1β were measured. Renal vascular was used to determine endothelial dependent contraction (EDC) and endothelial dependent relaxation (EDR). Protein levels were detected by Western blot. Human umbilical vein endothelial cells (HUVECs) were used to confirm the protective role of H2S against AngII‐induced cell injury.

Results

Exogenous NaSH administration significantly lowered SBP and ameliorated damaged EDR and EDC. H2S reduced the activation of NLRP3 inflammasome and oxidative stress in SHR. The endothelial protective and anti‐oxidant effect of H2S was abolished by LPS, an inducer of NLRP3 inflammasome. In HUVECs, H2S significantly ameliorated AngII‐induced cellular impairment, NLRP3 inflammasome and ROS generation. After knocking down of Nrf2, the above protective effect of H2S was abolished.

Conclusion

Hydrogen sulfide could inhibit vicious circle of oxidative stress and inflammation, resulted in improved endothelial function and ameliorated hypertension. Our results throw light on the crucial role of H2S in regulation of endothelial function, which might provide the new target for treatment of hypertension.

Support or Funding Information

This work was supported by the National Natural Science Foundation of China (31171098, 31671185), the Specialized Research Fund for the Doctoral Program of Higher Education of China (20121323110008), the Hebei Province for Innovation Talents Support Plan (LJRC017) and the Natural Science Foundation of Hebei (C2012206063, H2016206264).

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Endoplasmic Reticulum Stress Drives High Selenium‐Induced Endothelial Dysfunction
Authors: Agouni Abdelali , Zachariah Matshediso , Maamoun Hatem , Meira Lisiane , Rayman Margaret P.
Published: June 2021

Background

Selenium is an essential trace element important to human health. Nonetheless, supra‐nutritional selenium intake is reported to be associated with insulin resistance and may therefore increase the risk of diabetes and disrupt endothelial function (ED), the initial step in atherosclerosis development. However, the underpinning molecular mechanisms are not clear. High selenium concentrations cause apoptosis in cancer cells through the induction of endoplasmic reticulum (ER) stress, a mechanism also involved in the pathogenesis of ED. Therefore, we hypothesised here that high selenium intake could cause ED through the activation of ER stress response.

Methods

Human Umbilical Vein Endothelial Cells (HUVECs) were cultured with selenite at either physiological (0.5μM) or supra‐nutritional concentrations (5–20μM) for 8 to 24 hours in the presence or absence of a chemical chaperone, 4‐phenylbutryic acid (PBA). Then, mRNA expression of key ER stress response markers was analysed by qPCR. To assess endothelial function, we evaluated NO (Griess assay) release and Reactive Oxygen Species (ROS, flow cytometry) production. Finally, apoptosis (flow cytometry) and caspases 3/7 activity were measured.

Results

High selenium concentrations (5–20μM of selenite) compared to physiological concentration (0.5μM) or control enhanced mRNA expression of several ER stress markers such as CAAA/enhanced‐binding homologous protein (CHOP) [control (2.25±0.88), 0.5 μM (3.9±0.85), 10μM (36.2±6); n=5]. The pre‐incubation of cells with PBA completely reversed high selenium‐mediated ER stress. High selenite (5–20μM) also reduced NO production [control (2.27±0.07), 0.5μM (2.4±0.04), 10μM (1.8±0.05); n=5] and enhanced ROS production [control (18.9±1.93), 0.5μM (21.7±2.14), 10μM (68±0.65); n=5] compared to physiological concentration of selenite while cells pre‐treated with PBA were fully protected. Finally, supra‐nutritional concentrations of selenite increased the percentage of apoptotic HUVECs [control (2.96%±0.94), 0.5μM (3.92%±0.85), 10μM (43.7%±5.1); n=7] and augmented caspases 3/7 activity [0.5μM (0.45±0.08), 5μM (1.92±0.3) fold of control; n=5] compared to physiological concentration. Importantly, pre‐treatment of cells with PBA completely reversed high selenium‐mediated cell death.

Conclusions

We show here that high selenium treatment causes ED and cell death through the activation of ER stress. These results highlight the importance of a balanced selenium intake in order to achieve maximal health benefits. These findings underscore the importance to monitor cardiovascular risk development in cancer patients supplemented with high amounts of selenium as part of their chemotherapeutic intervention.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Effects of Ilex Guayusa Tea on Glycaemia, Cardiovascular Autonomic Modulation and Oxidative Stress in Streptozotocin‐Diabetic Rats
Authors: Stoyell‐Conti Filipe Fernandes , Mello Tafne C. , Dias Danielle S. , Bernardes Nathalia , Araujo Amanda A. , Santos Camila P. , Llesuy Susana F. , De Angelis Kátia
Published: June 2021

The incidence of cardiovascular diseases (CVD) increases significantly worldwide. Furthermore, it is the main cause of morbidity and mortality among diabetic patients. Rats induced to diabetes by streptozotocin (STZ) and untreated with insulin have similar alterations seen in humans, such as hyperglycemia, polydipsia, polyuria and weight loss, as well as cardiomyopathy, diabetic neuropathy and increased oxidative stress. Thus, the aim of this study was to verify the effects of ilex guayusa tea consumption on cardiovascular, autonomic, metabolic and oxidative stress alterations of an experimental model of diabetes. Thirteen Wistar rats were divided into two groups: Diabetic (D; n=7) and Diabetic + Ilex Guayusa (DG; n=6). Diabetes was induced by a single injection of STZ (50 mg/kg, iv.). Guayusa tea was administered for 21 days (3.0 g/L). Arterial pressure (AP) was directly measured. Oxidative stress was measured on heart and brain. At the beginning of the protocol glycaemia was similar between the groups (D: 330±32 vs. DG: 332±20 mg/dL). However, throughout the protocol, the D group showed a raise of glycaemia, evidenced by a greater area under the curve (AUC) (D: 1222±43 vs. DG: 1049±59 mg/dL*3 weeks). Indeed, increased glycaemia was associated with an increased oxidative profile. Positive correlations were observed between AUC of glycaemia and lipoperoxidation in the brain (r: 0.58; p: 0.04) and damage to protein in the heart (r: 67; p: 0.01). No differences in AP, heart rate and heart rate variability were observed between groups. However, regarding vascular sympathetic modulation, the D group had a reduction in LF‐SAP (1.3±0.3 vs. DG: 3.5±0.8 mmHg2) and VAR‐SAP (8.0±1.7 vs. DG: 15.0±1.7 mmHg2). This reduction in vascular sympathetic modulation, which in this model is considered a poor prognosis, was negatively correlated with AUC of glycaemia (AUC of glycaemia and VAR‐SAP, r: −0.57, p: 0.04). The results suggest a beneficial potential of guayusa tea consumption on metabolic, autonomic and oxidative stress in this model of diabetes.

Support or Funding Information

Universidade Nove de Julho

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Lack of endothelium‐derived ET‐1 accelerates diabetes‐mediated renal damage in female, but not male, mice
Authors: De Miguel Carmen , Pollock David M. , Pollocks Jennifer S.
Published: June 2021

Premenopausal females have smaller incidence and slower progression of kidney disease than males; however, diabetes‐induced kidney damage progresses similarly in both sexes. The vasoactive peptide endothelin‐1 (ET‐1) is upregulated in patients and animal models of diabetic nephropathy (DN), yet the specific role of endothelium‐derived ET‐1 in the development of DN remains unclear. These studies were designed to examine the role of vascular ET‐1 in diabetic kidney disease, and to determine if it is responsible for the loss of renal protection in diabetic females. Hyperglycemia was induced in male and female vascular endothelial cell ET‐1 knockout (VEET KO) and floxed mice via STZ (50 mg/kg i.p., 5 consecutive days). After 10 weeks of diabetes, urine and kidneys were collected and markers of glomerular damage, apoptosis (TUNEL assay) and immune cell infiltration were assessed. Histological examination revealed no significant differences in glomerular injury among the groups. However, in response to diabetes, female VEET KO mice presented significantly greater urinary protein excretion (6.0 ± 1.7 vs. 2.4 ± 0.8 mg/day; p<0.05; n=5–7/group) and cortical tubule dilation than diabetic male VEET KO mice. Albumin excretion and renal apoptosis were not significantly different between sexes or genotypes. Both diabetic female genotypes presented similar macrophage influx in renal cortex (VEET KO vs. floxed: 8.0 ± 0.8 vs. 7.9 ± 1.0 ED1+cells/field; n=9/group), and these values were significantly greater than diabetic males (VEET KO vs. floxed: 2.8 ± 0.9 vs. 3.7 ± 0.6 ED‐1+ cells/field; p<0.05; n=4–5/group). In addition, absence of vascular ET‐1 in females led to increased T cell infiltration in cortex (VEET KO vs. floxed: 8.7 ± 1.2 vs. 5.2 ± 0.4 CD3+ cells/field; p<0.05; n=9/group), but not in males (VEET KO vs. floxed: 5.7 ± 0.9 vs. 4.6 ± 1.0 cells/field; n=4–5/group). In conclusion, lack of endothelium‐derived ET‐1 accelerates the development of diabetes‐induced kidney damage in female, but not male, mice. These results highlight the protective role that vascular ET‐1 plays in females, but not males, against the development of DN.

Support or Funding Information

Funded by NIH T32 DK007545 to CDM and P01 HL95499 and P01 HL69999 and HL136936 to DMP and JSP.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.