bluuebunny/crossref_metadata_2025 huggingface dataset:
Vagally mediated low pressure baroreflex evokes biphasic changes in sympathetic nerve activity and resets the arterial baroreflex (1169.12)
Authors: Oga Yasuhiro , Kishi Takuya , Saku Keita , Kakino Takamori , Ikeda Masataka , Nishizaki Akiko , Kuwabara Yukimitsu , Ide Tomomi , Sunagawa Kenji
Published: June 2021

Background: Although volume loading activates the low pressure baroreflex (LBR), its quantitative impact on sympathetic nerve activity (SNA) and arterial baroreflex (ABR) remains unknown. The aim of this study is to clarify how the LBR affects SNA and ABR.

Methods/Results: In 10 anesthetized rats, we isolated carotid sinuses and controlled carotid sinus pressure (CSP). We infused dextran to activate LBR. We measured central venous pressure (CVP) and SNA. We fixed CSP at 90mmHg to abolish ABR. We infused dextran of 5% blood volume stepwise with or without vagotomy. In the low CVP range (2.6±0.8 to 4.5±0.7mmHg), volume loading increased SNA as much as 64.8±19.5% from the baseline, while further volume loading in the high CVP range (4.5±0.7 to 7.0±0.8 mmHg) returned SNA to the baseline level. Bilateral vagotomy totally abolished those changes in SNA. To assess the impact of LBR on the ABR central system, we changed CSP stepwise from 60 to 160 mmHg at the normal volume, mild volume loading and high volume loading while recording SNA responses. Mild volume loading (CVP: 3.8±0.6 mmHg) increased SNA by resetting the CSP‐SNA relation upward (+45.2%), while, high volume loading (CVP: 6.0±0.3 mmHg) decreased SNA by resetting the CSP‐SNA relation to the baseline level.

Conclusions: Volume loading evokes biphasic changes in SNA through the resetting of CSP‐SNA relation in ABR. LBR is a powerful modulator of sympathetic nervous system.
Effects of treatment with pyridostigmine on ECG, hemodynamics and connexin 43 after acute myocardial infarct in anesthetized rats (1169.13)
Authors: Santos Fernanda , Silva Carlos Alberto , Fazan Rubens , Girao Henrique
Published: June 2021

We evaluated the effect of acute treatment with pyridostigmine (PYR) an acetilconinesterase inhibitor on hemodynamics, ECG, survival rate and connexin 43 (Cx43), shortly after myocardial infarction (MI) in anesthetized rats.

Rats were anesthetized with urethane, and instrumented for ECG and arterial pressure (AP) recordings. After basal recordings, acute MI was induced by left coronary artery ligation followed by treatment with PYR (0.25 mg/kg, iv), or saline. ECG and AP were monitored during for 4h after MI when the animals had their hearts removed and retrogradely perfused with a Evans blue dye to determine the size of myocardial ischemia. The amount of Cx43 in left ventricle was also evaluated, by Western blot technique, in left ventricle of infarcted rats.

PYR caused a mild reduction in heart rate (438±8 to 387±10 bpm) with no change in AP. Infarcted rats treated with PYR showed lower incidence of arrhythmias and the percentage of rats that survived until the 4th hour after infarction was also higher in subjects that received PYR (72 vs 58%). Lengthening of QTc interval (Δ=33±13 ms) was observed in non‐treated, but not in PYR treated rats (Δ=‐2±4 ms). Finally, the amount of Cx43 in left ventricle was markedly reduced after MI (2.2±0.4 vs 0.72±0.1 au in non‐infarcted control rats). PYR administration also prevented the reduction in Cx43 (1.31±0.29 au) of infarcted rats.

Grant Funding Source: Supported by FAPESP, CNPq, CAPES, FAEPA.
TrkA mediated translocation of TRPv1 receptor is reduced in afferent neurons of cadiomyopathic rats (1169.16)
Authors: Nguyen Minh , Stout Laurence , Li Qinglu , Garry Mary
Published: June 2021

Previous studies have suggested that the decreased activity of TRPv1 receptor, a vanilloid receptor, plays a role in the development of an exaggerated exercise pressor reflex observed in the cardiomyopathic (CM) rat model. A requirement of TRPv1 activity is its localization to the cell membrane, which is mediated by the TrkA receptor. To determine if the translocation of TRPv1 is impaired in CM rats, we compared the levels of TRPv1 in the cell membranes of neurons from dorsal root ganglia (DRG) from normal and CM rats. Cells were stained for TRPv1 and fluorescence intensities of membrane and total cell were quantified. Localization of TRPv1 was evaluated in the presence or absence of Nerve Growth Factor (NGF) stimulation, and with a TrkA inhibitor in the presence of NGF. NGF treated neurons from normal animals displayed an increased ratio of membrane to total cell (M:T) TRPv1 as compared to untreated control. The addition of a TrkA inhibitor returned M:T to the level of non‐stimulated neurons. In the neurons from CM rats, NGF failed to increase the M:T, and treatment with TrkA inhibitor also did not change M:T level. These results suggest that DRG from CM rats are defective in their ability to translocate TRPv1 to the membrane upon NGF stimulation and this occurs via the TrkA receptor pathway.

Grant Funding Source: Supported by NIH 2R01HL070242‐07A2 (MGG)
Effect of vagal nerve stimulation on heart rate variability in a porcine model (1169.17)
Authors: Zhou Wei , Mahajan Arjun , Yamamoto Kent , Yamakawa Kentaro , Mahajan Aman
Published: June 2021

Sympathetic and parasympathetic nervous system imbalance has been strongly associated to sudden cardiac death. Vagal nerve stimulation (VNS), although a well‐recognized clinical therapy for epilepsy and medically refractory depression, is currently under investigation as a therapy for heart failure. Our objective of this study was to determine effects of left and right VNS on heart rate variability (HRV) by using power spectral analysis, the low frequency and high frequency components of heart rate variability. Ten anesthetized pigs received an application of either right or left VNS at 15 Hz for 20 second. Right and left VNS resulted in a decrease in heart rate from 82.6±8.3 to 75.3±9.2 and 91.5±5.0 to 85.5±4.9, respectively. Right VNS significantly decreased low frequency normalized units (LF n.u.) component (60.4±4.4 vs. 38.8±6.3 baseline, p<0.05) indicating a reduced sympathetic nerve activity and increased high frequency normalized units (HF n.u.) component (23.0±4.8 vs. 46.4±6.5, p<0.05) indicating an enhanced parasympathetic nerve activity. In contrast, Left VNS did not alter either LF n.u. (37.7±12.1 vs 37.3±10.8 baseline) or HF n.u. (34.1±7.1 vs. 32.0±7.0 baseline). In conclusion, right but not left VNS modulates sympathetic and parasympathetic activity and may serve as a potential therapy to treat cardiovascular diseases.
Arrhythmias evoked by airway nociceptive reflexes in healthy and cardiovascular diseased rats (1169.8)
Authors: Hooper Justin , Taylor‐Clark Thomas
Published: June 2021

Inhalation of particulate matter (PM) increases cardiovascular (CV) morbidity and mortality by increasing the risk of arrhythmias in susceptible individuals. This is believed to occur through autonomic nervous system imbalance following activation of pulmonary afferent C‐fibers. However, it is unclear how pulmonary‐cardiac reflexes specifically contribute to these arrhythmias. To characterize this, we selectively activated pulmonary C‐fibers via gating of ion channels TRPV1 and TRPA1 (which can be activated by PM) using capsaicin and mustard oil (MO), respectively. We implanted 15 week old Sprague‐Dawley (SD) and Spontaneously Hypertensive (SH) rats with a radiotelemetric ECG device. ECG was recorded for 30 minutes during exposure of the rats to ambient air, nebulized vehicle, and either capsaicin (600 μM) or MO (30 mM). We found an increase in dropped beats and arrhythmias such as second‐degree AV block and premature ventricular contractions in both SD and SH rats upon irritant inhalation. Furthermore, SH rats had a significant increase in brady/tachy events upon agonist inhalation. We conclude that lung C‐fiber reflexes evoke arrhythmias, which in CV disease may contribute to morbidity and mortality.
Blueberries exert antihypertensive and vascular‐protective effects in postmenopausal women with pre‐ and stage 1‐hypertension (117.6)
Authors: Johnson Sarah , Figueroa Arturo , Navaei Negin , Wong Alexei , Kalfon Roy , Feresin Rafaela , Elam Marcus , Payton Mark , Arjmandi Bahram
Published: June 2021

Postmenopausal women have a high prevalence of hypertension (HTN) and often develop arterial stiffness which increases their risk for developing cardiovascular disease. Although antihypertensive drug therapies exist, increasing numbers of people prefer natural therapies. In vivo studies have demonstrated the antihypertensive and vascular‐protective effects of blueberries. Therefore, the objective of this study was to examine the effects of 22 g freeze‐dried blueberry powder (BB) or 22 g control (CON) per day for 8 weeks on blood pressure and arterial stiffness in forty postmenopausal women with pre‐ and stage 1‐HTN. Resting brachial systolic and diastolic blood pressures (SBP and DBP, respectively) were evaluated and arterial stiffness was assessed using carotid‐femoral pulse wave velocity (cfPWV) and brachial‐ankle pulse wave velocity (baPWV). Blood was collected at baseline, 4 and 8 weeks to assess nitric oxide (NO). After 8 weeks of BB treatment, SBP and DBP (– 7 mmHg, P < 0.05 and – 5 mmHg, P < 0.01, respectively) and baPWV (– 97 cm/s, P < 0.01) were significantly lower than baseline levels and there were significant (P < 0.05) group by time interactions, whereas there were no changes in CON. NO levels were significantly (6.24 µM, P < 0.01) increased in the BB group at 8 weeks compared to baseline values whereas there were no changes in CON. The results of this study indicate that regular consumption of blueberries is of benefit to vascular health.

Grant Funding Source: Supported by The U.S. Highbush Blueberry Council
Daily almond consumption (1.5 oz./d) decreases abdominal and leg adiposity in mildly hypercholesterolemic individuals (117.8)
Authors: Berryman Claire , West Sheila , Fleming Jennifer , Bordi Peter , Kris‐Etherton Penny
Published: June 2021

Almonds are an energy‐dense food that do not promote weight gain or increased waist circumference (WC); however, the effects of almond consumption on total body and sub‐regional fat and lean mass distribution have not been evaluated. Therefore, a randomized, 2‐period (6 wk/period), crossover, controlled‐feeding study was designed to investigate the effects of 1.5 oz./d almonds vs. a calorie‐matched, high CHO snack, within the context of a cholesterol‐lowering diet, on measures of body composition. Differences in nutrient profiles of the control (CON: 58% CHO, 15% PRO, 26% FAT, no almonds/d) and almond (ALD: 51% CHO, 16% PRO, 32% FAT, 1.5 oz. of almonds/d) diets were due to nutrients inherent to each snack and did not differ in saturated fat or cholesterol. Subjects (n=52) were generally healthy adults (BMI 26.3 ± 0.4 m/kg2) with elevated LDL‐C (148.0 ± 2.7 mg/dl). Total body mass (weight), fat mass, and lean mass were not different on the two diets. ALD reduced overall abdominal mass, abdominal fat mass, and abdominal lean mass vs. CON (‐0.20 ± 0.08, ‐0.07 ± 0.03, and ‐0.13 ± 0.06 kg, respectively; P 蠄0.04). WC also was decreased by ALD compared to CON (‐0.67 ± 0.31 cm; P=0.03). Moreover, ALD decreased leg fat mass compared to CON (‐0.12 ± 0.05; P=0.02). Incorporation of almonds in a cholesterol‐lowering diet decreases sub‐regional fat depots, including abdominal adiposity, an important risk factor for metabolic syndrome.

Grant Funding Source: Supported by the Almond Board of California
Increased pressure gradient across veins in human limbs induces sympathetic activation (1170.1)
Authors: Cui Jian , Blaha Cheryl , Herr Michael , Muller Matthew , Drew Rachel , Sinoway Lawrence
Published: June 2021

We showed that venous distension induced by saline infusion into veins of an arterially occluded arm evokes reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP). We have also observed that negative pressure on an occluded limb increases MSNA. We speculate that the responses with these two models are evoked through a similar mechanism. To examine this question, BP, heart rate, and MSNA were assessed in 11 young healthy subjects, when 100 mmHg negative pressure was applied on an arterially occluded limb (termed “NPOL”) for 2 min. Limb occlusion without suction was used as a control. In a separate visit, saline (5% arm volume) was infused into veins of the arterially occluded arm. Both NPOL and the saline infusion into the occluded arm significantly increased MSNA and BP. Both MSNA (R=0.643 for arm, R=0.664 for leg) and BP (R=0.786 for arm, R=0.522 for leg) responses during NPOL were significantly correlated with the responses with the saline infusion into the arm. The MSNA and BP responses during saline infusion were not correlated with the responses during limb occlusion. These observations suggest that the mechanisms responsible for sympathetic activation during limb suction are similar to those seen during infusion induced venous distension. Thus, the NPOL model can be employed to study the venous distension reflex.

Grant Funding Source: Supported by NIH P01 HL096570 (LIS) and UL1 TR000127 (LIS)
Sensory nerve‐mediated vasodilation is reduced in plantar metatarsal arteries from spinal cord injured rats (1170.15)
Authors: Brock James , Shafik Christopher
Published: June 2021

Axon‐reflex mediated vasodilation is reduced in skin of spinal cord injured humans (SCI). This change is suggested to produce altered skin function, an increased risk of pressure sores and slow wound healing. This study investigated the interaction between sympathetic and sensory nerve‐mediated effects in plantar metatarsal arteries (PMAs) from T10 spinal cord transected and sham‐operated (control) rats. Six weeks post‐surgery, PMAs were dissected and mounted isometrically in wire myographs. In control PMAs, activation of the perivascular nerve fibers with trains of 100 pulses at 1 Hz evoked contractions that peaked at ~10th pulse (1.1 ± 0.1 mN/mm) and then declined to ~40% (41 ± 5%) of the peak value at the 100th pulse. In PMAs from SCI rats, the peak amplitude of contraction was ~2‐fold larger (2.1 ± 0.2 mN/mm, P < 0.01) and the decline during the train of stimuli was smaller (declined to 94 ± 5 % of peak value). Treatment with capsaicin to inhibit the vasodilator action of the primary afferent nerve fibers did not greatly change the peak amplitude of nerve‐evoked contractions in PMAs from either control or SCI rats. However, in control PMAs, the decline in contraction during the train of stimuli was markedly reduced, with the contraction measured at the 100th pulse being increased by ~155% (155 ± 40 %). The % increase in amplitude of contractions measured at 100th pulse was much smaller in PMAs from SCI rats (20 ± 6%, P < 0.01). In conclusion, these findings indicate that the decline in sympathetic nerve‐mediated contraction during trains of stimuli is produced by co‐activation of primary afferent nerve fibers and that this effect was greatly reduced in PMAs from SCI rats. This finding may explain why axon reflex‐mediated vasodilation is reduced in skin of SCI humans.

Grant Funding Source: Supported by the NHMRC of Australia
Exploring social stress though pharmacological manipulation of pair bonds in prairie voles (1171.2)
Authors: McNeal Neal , Scotti Melissa‐Ann , Woodbury Matthew , Ihm Elliott , Colburn William , Cacioppo Stephanie , Cacioppo John , Grippo Angela
Published: June 2021

Supportive social relationships positively influence health, whereas negative relationships have an adverse effect. This preliminary experiment investigated the hypothesis that suppressing central oxytocin activity in male prairie voles would alter pair interactions, thereby inducing behavioral and cardiovascular changes in their associated female partners. Female prairie voles were implanted with radiotelemetry transmitters and paired with an unrelated male. In phase 1, male partners received 7 days of an oxytocin antagonist (OTA; 10mg/kg/day ip) concurrently during housing with the females. Depressive behaviors and cardiovascular function were measured in the females. Females whose male partners received OTA displayed higher resting blood pressure (BP) and heart rate (HR), and higher levels of depression‐like behaviors in a behavioral test, vs. those whose partners received vehicle. In phase 2, females were isolated from the male partners for 6 days, plus 6 days of additional mild stressors. Females exhibited higher BP and HR, regardless of whether the male partner previously had received OTA or vehicle. These preliminary findings indicate that oxytocinergic mechanisms may underlie male‐female social interactions to influence responses to stress, and inform our understanding of the role of social relationships in mediating stressor reactivity in humans.

Grant Funding Source: HL112350
Reflex control of renal sympathetic nerve activity in heart failure is preserved in ovary intact female rats (1171.3)
Authors: Pinkham Maximilian , Guild Sarah‐Jane , Malpas Simon , Barrett Carolyn
Published: June 2021

Following myocardial infarction (MI), pathological increases in sympathetic nerve activity (SNA) drive the development and progression of heart failure. The current study investigated the effects of female sex and ovarian hormones on arterial baroreflex and cardiac sympathetic afferent reflex (CSAR) control over renal SNA in MI‐induced heart failure. 6 weeks post MI or sham surgery , arterial pressure and renal SNA responses were recorded in chloralose‐urethane anesthetized male, female and ovariectomized female (OVX) rats. In male and OVX MI groups, arterial baroreflex control of renal SNA was significantly impaired compared to shams, due mostly to an impaired ability to inhibit SNA. In ovary‐intact females, arterial baroreflex control of renal SNA was unaltered in MI animals compared to sham. CSAR mediated increases in renal SNA were significantly augmented in male and OVX MI groups when compared to ovary‐intact female MI group. The current study is the first to describe a protective effect of ovarian hormones on reflex control of SNA in MI‐induced heart failure.

Grant Funding Source: Lottery Health New Zealand and University of Auckland Faculty Research Development Fund
Pregnancy increases sympathetic nerve activity: role of the arcuate nucleus (1171.5)
Authors: Shi Zhigang , Brooks Virginia
Published: June 2021

Normal pregnancy increases sympathetic nerve activity (SNA), which is further elevated in hypertensive disorders like preeclampsia. However, the mechanisms are unknown. The arcuate nucleus (ArcN), recently identified as a regulator of SNA, undergoes profound changes during pregnancy and other reproductive states. Therefore, we tested the hypothesis that the ArcN contributes to the elevated SNA during pregnancy, by determining if inhibition of the ArcN with the GABAA agonist, muscimol (30 pmol in 30 nL), decreases SNA and mean arterial pressure (MAP) more in late pregnant (P) compared to nonpregnant (NP) SD α‐chloralose anesthetized rats. Compared to NP rats, P rats exhibited lower MAP (P: 83±3 mmHg, n=12; NP: 111±4 mmHg, n=13; P<0.05), higher HR (P: 420±8 bpm, n=12; NP: 367±12 bpm, n=13; P<0.05), elevated lumbar SNA (LSNA; P: 1.9±0.2 µV, n=4; NP: 0.6±0.2 µV, n=4; P<0.05) and elevated splanchnic SNA (SSNA; P: 3.5±0.7 µV, n=4; NP: 0.9±0.2 µV, n=5; P<0.05); renal SNA (RSNA) was not significantly different between groups (P: 5.3±1.7, n=4; NP: 4.2±0.9 µV, n=4). In pregnant rats, ArcN nanoinjection of muscimol significantly decreased (P<0.05) MAP (‐13.3±1.6 mmHg), HR (‐14.5±1.6 bpm), LSNA (‐14.9±3.1% control), SSNA (‐14.4±1.8 % control), and RSNA (‐12.6±0.6 % control). ArcN muscimol did not significantly alter these variables in NP rats. In conclusion, these data suggest that, during pregnancy, the ArcN contributes to sustained increases in sympathetic tone to multiple organs.

Grant Funding Source: Supported by HL088552 and AHA.
Tonic GABAergic inhibition of RVLM neurons: a novel target for sympathetic control (1172.3)
Authors: Gao Hong , Derbenev Andrei
Published: June 2021

The rostral ventrolateral medulla (RVLM) is a critical component of the sympathetic nervous system regulating homeostatic functions including arterial blood pressure (ABP). GABAA receptors mediate the majority of inhibition in the brain and GABAergic inhibition of preautonomic neurons in the RVLM is well accepted. Decreased inhibition of RVLM neurons increases sympathetic nervous system activity and thereby elevates ABP. Despite our increasing understanding of the functional significance of GABAA receptors in the regulation of neuronal excitability, the mechanisms underlining synaptic and extrasynaptic control of preautonomic neurons in the RVLM is unknown. Using the transsynaptic retrograde viral tracer, PRV‐152, we identified preautonomic neurons in the RVLM. We found that RVLM neurons displayed persistent, tonic current to GABA, via GABAA receptors, in the absence of large‐scale phasic neurotransmission using whole‐cell patch‐clamp recordings. Application of the GABAA receptor blocker bicuculline (30 µM), revealed a robust somatic tonic inhibitory current mediated by extrasynaptic GABAA receptors with an average amplitude of 196.3 ± 39.3 pA. Our data suggest that extrasynaptic tonic current mediated by GABAA receptors plays a major role in determining the resting membrane potential and firing activity of preautonomic neurons in the RVLM.

Grant Funding Source: NIH P30GM103337
Interleukin 6 derived from macrophages enhances angiotensinogen expression in renal proximal tubular cells (1173.3)
Authors: Satou Ryousuke , Miyata Kayoko , Navar L. Gabriel
Published: June 2021

Chronic angiotensin II (Ang II) infusion leads to hypertension, intrarenal renin‐angiotensin system activation, stimulation of proximal tubular AGT and renal MΦ infiltration. Treatment with immunosuppressive drugs reduces MΦs infiltration, intrarenal Ang II levels and blood pressure, suggesting that MΦ contribute to intrarenal RAS activation and hypertension. However, the contribution of MΦ to AGT augmentation has not been delineated. To elucidate the role of MΦ in AGT augmentation, cultured rat MΦ were treated with 0.05‐5 μM Ang II up to 48 h. After removal of MΦ, the culture medium was incubated with rat PTC for 24 h. mRNA levels of interleukin 6 (IL‐6) in MΦ and AGT in PTC were evaluated by real‐time RT‐PCR. Treatment with 5 μM Ang II activated p38 MAP kinase and increased IL‐6 expression (2.65 ± 0.11, ratio to control) at 48 h; this response was attenuated by AT1 receptor blockade with olmesartan. Incubation of PTC with the culture medium of Ang II‐stimulated MΦ increased AGT expression in PTC (1.71 ± 0.49 by 5 μM Ang II). A neutralizing IL‐6 antibody added to culture medium attenuated the AGT augmentation in PTC (1.17 ± 0.27). These results demonstrate that Ang II mediated increases in IL‐6 production by MΦ increase AGT expression in PTC, suggesting that the Ang II mediated accumulation of MΦ in the kidney stimulates IL‐6 production in the MΦ, which augments intrarenal AGT expression contributing to hypertension.
Relaxation of human airway smooth muscle cells (1174.1)
Authors: Fitzgerald Robert , Lee Danielle , Panettieri Reynold , Wang Rui , An Steven
Published: June 2021

The purpose of this study was to determine if H2S relaxed human airway smooth muscle cells. If so, we explored the mechanisms responsible for the phenomenon. Human airway smooth muscle cells (HASM) were prepared from human bronchi obtained from lungs unsuitable for transplantation. Dynamic changes in stiffness were measured as an indicator of contraction and relaxation of isolated HASM, using Magnetic Twisting Cytometry (MTC). Acute exposure of the cells to two agents capable of generating H2S, Na2S and GYY4137, decreased cell stiffness in a dose‐dependent fashion, with maximal relaxation at 10mM and 5mM, respectively. In addition, cells exposed to varying doses of GYY4137 for 24 hours exhibited dose‐dependent decreases in cell stiffness that were substantially greater than acute responses (21% relaxation at 300s vs 50% relaxation at 24h). We further determined that, like vascular smooth muscle, HASM exhibited the presence of ATP‐sensitive K channels and the H2S synthesizing enzyme, cystathionine‐g‐lyase. These findings demonstrated that smooth muscle in the airways react to H2S quite similarly to that in the vasculature, and suggest, thereby, this class of small gas molecules can be exploited for treating constricted human airways, such as found is asthma.

Grant Funding Source: HL50712‐13 HL107361
Non‐genomic relaxation effect of testosterone through L‐type and store operated Ca2+ channels blockade in guinea pig airway smooth muscle (1174.2)
Authors: Montaño Luis , Perusquía Mercedes , Flores‐Soto Edgar
Published: June 2021

In vascular smooth muscle, testosterone (TES) produces relaxation blocking L‐type Ca2+ channels. Recently, we found that L‐type and store operated (SOC) Ca2+ channels are the main membranal structures that provide extracellular Ca2+ for carbachol‐induced contraction in airway smooth muscle (ASM). Thus, we studied the possible interactions between L‐type and SOC channels in TES‐induced relaxation in guinea pig ASM. TES (10, 32 and 100 μM) induced a complete relaxation of Cch pre‐contracted tracheal smooth muscle and indomethacin partially inhibited this response. In single myocytes, the KCl induced intracellular Ca2+ increase ([Ca2+]i) was decreased by 32 and completely blocked by 100 nM TES. This androgen (32 and 100 μM) significantly diminished (~25 and 49 %, respectively) the capacitative Ca2+ entry. Myocytes stimulated with carbachol (Cch) produced a transient Ca2+ peak followed by a sustained plateau and 100 μM TES completely abolished the Cch induced Ca2+ plateau. Indomethacin, significantly diminished this effect of TES. When D‐600 was added during the plateau phase, a partial diminution (~35 %) was observed. A grater decrease (~78 %) was also seen when 2‐APB (SOC antagonist) was used. The combination of both drugs completely abolished the Ca2+ plateau induced by Cch. We concluded that TES blocks L‐type Ca2+ channels at nanomolar and SOC channels at micromolar concentration to induce relaxation.

Grant Funding Source: PAPIIT‐DGAPA, UNAM IN200613
Muscarinic receptor agonist‐induced constriction of airway smooth muscle is attenuated by carbon monoxide via increased cGMP production (1174.4)
Authors: Jakupaj Muharrem , Lajçi Azem , Temaj Gazmend , Cenaj Asllan , Sopi Ramadan
Published: June 2021

Previously we have shown that carbon monoxide (CO) potentiates electrical field stimulation‐induced relaxation of airway smooth muscle (ASM). However, the effect of CO on ASM contractile responses induced by muscarinic receptor signaling is not well understood. Therefore, this study aimed to investigate the effect of CO on contractile responses of rat tracheal smooth muscle (TSM) induced by a muscarinic agonist. Tracheal segments were excised from 28 day‐old rats. Dose‐response curves to methacholine (MCh) were constructed in absence or presence of the CO precursor ‐ hematin (10 µM); heme oxigenase (HO) inhibitor tin protoporphyrin‐IX (SnPP‐IX; 100 µM); and/or soluble guanylyl cyclase inhibitor 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ; 10 µM). Preincubation of tissues with CO precursor ‐ hematin attenuated the MCh‐induced contractile responses of TSM. This effect of hematin was reversed by SnPP‐IX and/or ODQ, indicating the role of CO. According to the results we conclude that CO or its precursors might be an important target therapy to be used for treatment of medical conditions associated with airway hyper‐constriction.
Breathing 100% O2, but not 40% O2, during exercise reduces blood flow through intrapulmonary arteriovenous anastomoses (1175.7)
Authors: Davis James , Elliot Jonathan , Duke Joseph , Futral Joel , Lovering Andrew
Published: June 2021

Blood flow through intrapulmonary arteriovenous anastomoses (IPAVA), detected using saline contrast echocardiography, is known to increase during exercise breathing room air but is reduced or eliminated during exercise breathing a fraction of inspired oxygen (FIO2) = 1.0. Although the mechanism(s) for this hyperoxia‐induced reduction in blood flow through IPAVA remain unknown, it is also unknown if FIO2’s <1.0 have the same effect. Thus, we sought to determine the effects of varying hyperoxic FIO2’s on blood flow through IPAVA. Five subjects (4 male) without a patent foramen ovale completed five, 4 min bouts of constant‐load cycle ergometer exercise (Males ‐ 250 W, Females ‐ 175 W), breathing a FIO2 = 0.21, 0.40, 0.60, 0.80 and 1.0 in a random, balanced order. Each exercise bout was preceded by 15 min of rest breathing the prescribed FIO2 to allow for complete gas partial pressure equilibration. Blood flow through IPAVA was detected using saline contrast echocardiography at rest and 3 min into each exercise bout. Bubble scores at FIO2 = 0.21 and 0.40 did not differ from one another, and were significantly greater than all other FIO2’s. These data suggest that hyperoxia‐induced decreases in IPAVA blood flow occur in a dose‐dependent manner.
mAChR activation induces epithelial‐mesenchymal transition on lung epithelial cells (1176.10)
Authors: Li Juan , Xu Lu , Cui Yong‐Yao , Chen Hong‐Zhuan
Published: June 2021

Objective: Epithelial‐mesenchymal transition (EMT) is a physiological process that plays important role in pathogenesis of chronic obstructive pulmonary disease (COPD). Although a number of molecules involved in ACh‐mediated airway inflammation and remodeling have been identified, little is known regarding the role of ACh in EMT. In this study, we examined the effects of ACh on TGF‐β1‐induced EMT, and the pathway involved in these processes Methods: Human lung epithelial cells were stimulated with carbachol, an analogue of ACh, and epithelial and mesenchymal marker proteins were evaluated using western blot and immunofluorescence analyses.

Results: Decreased E‐cadherin expression and increased vimentin and α‐SMA expression induced by TGF‐β1 in the human alveolar epithelial cell line (A549) were significantly abrogated by the non‐selective mAChR antagonist atropine and enhanced by the acetylcholinesterase inhibitor physostigmine. An EMT event in lung epithelial cells also occurred in response to physostigmine alone. Furthermore, ChAT express and ACh release by A549 cells were enhanced by TGF‐β1 which release also trigged by ACh analogue carbachol. Interestingly, mAChR stimulation with carbachol also induced EMT in alveolar epithelial cells (A549) as well as in bronchial epithelial cells (16HBE) in a time‐ and concentration‐dependent manner, the induction of carbachol was abrogated by selective antagonist of M1 (pirenzepine) and M3 (4‐DAMP) mAChRs, but not by M2 (methoctramine) antagonist. Carbachol‐induced EMT occurred through phosphorylation of Smad2/3 and ERK, which was also inhibited by pirenzepine and 4‐DAMP.

Conclusions: Our findings indicate that mAChR activation, perhaps via M1 and M3 mAChR, induced lung epithelial cells to undergo EMT and a cooperative regulation by mAChR activation and TGF‐β1 expression was involved in EMT, leading to airway remodeling.

Grant Funding Source: Supported by National Natural Science Foundation of China Nos.30873109 and 81173084
Pseudomonas aeruginosa infection causes endothelial cell Tau aggregation: evidence for an endothelial tauopathy (1176.5)
Authors: Morrow Kyle , Ochoa Cristhiaan , Alexeyev Mikhail , Frank Dara , Balczon Ronald , Stevens Troy
Published: June 2021

Our laboratory recently demonstrated that Pseudomonas aeruginosa exoenzyme Y (ExoY) stimulates Tau hyperphosphorylation and insolubility ‐ hallmarks of a “Tauopathy”. Unlike neurodegenerative Tauopathies, we did not observe formation of Tau aggregates indicating that other pathogenic factors may be required to elicit a full spectrum Tauopathy. Thus, we tested whether P. aeruginosa ExoU induces Tau aggregation, causing an acute infectious Tauopathy. Pulmonary microvascular endothelial cells (PMVECs) were engineered to conditionally (Tet‐On) express codon‐optimized activity‐attenuated mutant ExoU encoding both myc‐ and protein degradation domain‐epitopes. Multiple strains of P. aeruginosa have been generated that allow systematic investigation of exoenzyme function. The background bacterial strain is PA103, a clinically relevant strain that possesses ExoU. We also used a strain that introduces only ExoY (ExoY+) to infect PMVECs. PMVEC gap formation was induced in a time‐dependent manner following ExoY+ infection as well as by doxycycline‐induced ExoU expression or PA103 infection. Cell extracts and supernatants were collected and immunoblotted with pan‐Tau and Tau oligomer‐specific antibodies. Gap formation was paralleled by a loss in intracellular Tau expression and hyperphosphorylation, with an increase in extracellular Tau oligomers. ExoU induces endothelial cell Tau release and aggregation, suggesting P. aeruginosa causes an endothelial Tauopathy.

Grant Funding Source: HL66299, HL60024
Development of respiratory pattern in mice (1177.1)
Authors: Bissonnette John , Knopp Sharon
Published: June 2021

Maturation of mouse respiratory pattern in vivo has been studied (Euro J Neurosci 17:1233, 2003). The results, however, were grouped at P0‐P2. In vitro recordings from en block late embryonic rat brainstem spinal cord preparation showed prolonged neuronal activity in cervical ventral root 5 bursts (J Neurophysiol 67:996, 1992). Here we show in C57BL6/J mice a change in respiratory pattern from P0.5 to P2. Studies were performed with body plethysmography at ~32°C. This system (J Appl Physiol 56:1533, 1984) determines inspiratory and expiratory flow. At P0.5 (wt=1.38±0.08g) TI showed a sustained plateau pattern lasting 253±17 ms. TE (173±14 ms) was shorter resulting in a duty cycle (TI/TTOT) of 0.59±0.01. Respiratory frequency increased from 145±9 bpm at P0.5 to 188±19 at P2 (wt=1.73±.05g). The increase in frequency was entirely due to a change in TI that decreased from 253±17 to 135±11 ms. Inspiratory flow no longer showed a plateau during most breaths. TE remained constant over the first 2 postnatal days (173±14 vs 208±22 ms). TI/TTOT was reduced from 0.59±0.01 to 0.40±0.01. The results suggest that pontine pneumotactic centre and/or its afferent inputs are no fully mature in P0.5 mice.

Grant Funding Source: Supported by Rett Syndrome Research Trust
Inspiratory occlusion pressure as a measure of hypoxic ventilatory drive (1178.14)
Authors: Gaio Eduardo , De La Zerda David , Soler Xavier , Ries Andrew , Powell Frank
Published: June 2021

The pressure generated during the first 0.1 sec of an occluded inspiration (P0.1) has been proposed as a measure of neural ventilatory drive that is independent of respiratory mechanics. We attempted to validate P0.1 as a measure of hypoxic ventilatory drive against traditional measurement of the isocapnic hypoxic ventilatory response (HVR). Ten healthy subjects breathed through a mask and non‐rebreathing valve. The HVR ([[Unsupported Character ‐ Symbol Font □]]Ventilation / ‐[[Unsupported Character ‐ Symbol Font □]]SaO2) was measured when inspired O2 decreased from 30% to 10% and end‐tidal PCO2 was held constant 2‐3 Torr above the level measured on 30% O2. The change in P0.1 (averaged over 3 randomly occluded breaths) was measured under the same conditions. HVR averaged 0.87 + 0.62 L/(min %) and the change in P0.1 with hypoxia was 0.16 + 0.12 cm H2O/%; the two responses were not correlated across all subjects. HVR was < 0.10 in 3 subjects but only 2 of these subjects had a low P0.1 response (<0.06) and another subject with a P0.1 response < 0.06 had HVR > 0.10. Reanalysis of previous HVR data collected in our laboratory shows the HVR is not significantly different within subjects (n=6) between 2 trials in 1 day, or between 4 trials over 4 days. Additional measurements of P0.1 hypoxic response reproducibility are necessary to evaluate if it can be used to test for time‐dependent changes in the HVR of patients with hypoxemia from chronic lung disease.

NIH RO1 HL‐081823, P01 HL‐098053 and CAPES‐10326/12‐0

Grant Funding Source: NIH RO1 HL‐081823, P01 HL‐098053 and CAPES‐10326/12‐0
Dorsolateral PAG mediates respiratory arousal in rats (1178.3)
Authors: Monteiro Matheus , Mendes‐Junior Leônidas , Guimaraes Drielle , Nalivaiko Eugene , Braga Valdir
Published: June 2021

Our aim was to determine whether dorsolateral PAG (dl‐PAG) mediates respiratory responses to novel environment, sudden stimuli and restraint stress. Guide cannulas were implanted bilaterally in 6 adult male Wistar rats. On different days, either saline of GABAA agonist muscimol (100 pg/200 nl) were microinjected into the dl‐PAG, and respiratory signal was recorded using whole‐body plethysmography during adaptation period (30 min), following presentation of acoustic stimuli (500‐ms white noise at 70, 80 and 90 dB), and during restraint. Placing animal in the plethysmograph elicited exploratory behaviour, including vigorous sniffing; blockade of the dl‐PAG substantially attenuated these changes. Acoustic stimuli elicited short‐latency tachypneic responses; administration of muscimol did not affect their amplitude but increased latency of responses to 80‐ and 90‐dB stimuli. Restraint stress provoked sustained increase in the dominant respiratory rate associated with the fraction of time spent at high (>250 cpm) respiratory frequency; blockade of dl‐PAG attenuated the later effect. We conclude that the integrity of the dl‐PAG is essential for mediating respiratory changes associated with active coping.

Grant Funding Source: Supported by Capes PVE 088/2012 and CNPq
Angiotensin‐(1‐7) improves engraftment and reparative potential of cardiac progenitor cells in a rat model of myocardial infarction (1180.17)
Authors: Qi Yanfei , Bruce Erin , Shenoy Vinayak , Vohra Ravneet , Cole‐Jeffrey Colleen , Abbatematteo Joseph , Zingler Michael , Walter Glenn , Pepine Carl , Katovich Michael , Raizada Mohan
Published: June 2021

Angiotensin‐(1‐7) [Ang‐(1‐7)] has been shown to produce a multitude of effects on endothelial progenitor cells, implicating a role for this peptide in vascular repair. Our studies have shown that Ang‐(1‐7) enhanced proliferative and tube‐forming abilities of cardiac progenitor cells (CPCs), prevented hypoxia‐induced inhibition of migration and protected them against H2O2‐induced cell death. These observations have led us to hypothesize that Ang‐(1‐7) would enhance CPCs reparative capacity and improve cardiac function in a rat model of myocardial infarction (MI). CPCs alone or CPCs overexpressing Ang‐(1‐7) (4 × 106) were intravenously injected into MI rats and cardiac functions were examined to test this hypothesis. Rats with MI exhibited reduced ejection fraction (EF, 33.0% ± 1.5 vs 77.0% ± 3.9 for control), increased left ventricular hypertrophy [VH, 3.6 ± 0.1 vs 2.7 ± 0.1 for control, (g/kg)], and decreased contractility (dP/dtmax, 7235 ± 271.9 vs 10394 ± 326.3 for control, mmHg/sec). Compared with untreated MI rats, administration of CPCs alone restored EF by 42%, decreased VH by 11%, and improved dP/dtmax by 23%; remarkably, treatment with CPCs overexpressing Ang‐(1‐7) improved EF by 79%, decreased VH by 17%, and attenuated the reduction in dP/dtmax by 42%. Furthermore, Ang‐(1‐7) enhanced the engraftment of CPCs by two‐fold in the peri‐infarct myocardium. These observations demonstrate that Ang‐(1‐7) potentiates functionality and improves engraftment of transplanted CPCs to protect against MI. Thus, genetic modification of CPCs with Ang‐(1‐7) could be a valuable therapeutic strategy for ischemic heart diseases.
Luminal 5‐HT induces HCO3‐ secretion via 5‐HT4 in rat proximal colon (1181.11)
Authors: Kaji Izumi , Akiba Yasutada , Kaunitz Jonathan
Published: June 2021

5‐hydroxytryptamine (5‐HT), contained in enterochromaffin cells, is abundantly produced throughout the gastrointestinal tract. 5‐HT is released into the gut lumen and into the submucosa, although reports of its luminal activity and function, with particular reference to ion transport, are infrequent. In rat proximal colon, short‐circuit current (Isc), as measured in Ussing‐chambered mucosa‐submucosa preparations, was gradually increased to a sustained value following the luminal application of 5‐HT (10 ‐ 100 μM). Increasing in Isc was NKCC1‐independent but carbonic anhydrase‐dependent, consistent with electrogenic HCO3‐ secretion. The neurotoxin tetrodotoxin (TTX) or cyclooxygenase (COX) inhibitor indomethacin did not alter the response to luminal 5‐HT. Pretreatment with forskolin abolished the response to luminal 5‐HT, indicating that cAMP mediates 5‐HT‐induced ion secretion. Luminal pretreatment with the 5‐HT4 receptor antagonist GR113808 (1 μM), but not with 5‐HT2 or 5‐HT6 antagonists, inhibited the response to luminal 5‐HT, whereas serosal GR113808 had no effect. Furthermore, the luminal 5‐HT4 agonist cisapride increased Isc to the same extent as did 5‐HT. These results suggest that a novel mucosal 5‐HT4‐mediated HCO3‐ secretory pathway is present in the colon. Luminal 5‐HT4 may be important in the maintenance of luminal pH and pCO2, while preserving adequate luminal fluid volume.

Grant Funding Source: VA Merit Review, NIH R01 DK54221, JSPS
Blunted increases in vertebral blood flow during L‐arginine infusion in patients with hypertension (1183.5)
Authors: Vianna Lauro , Fernandes Igor , Barbosa Thales , Amaral Tatiana , Rocha Natalia , Secher Niels , Nóbrega Antonio
Published: June 2021

Arterial hypertension (AH) has detrimental effects on the physiological mechanisms that regulate blood supply to the brain. However, little is known about the impact of human AH on cerebral endothelial function. In 21 men, 13 hypertensive patients (46±3 yr) and 8 age‐matched controls (Ctrl; 44±4 yr), blood pressure (Finometer) and blood flow (Doppler) in the main arteries delivering blood to the cortex (common carotid, CC) and brainstem (vertebral, VA) were simultaneously measured at rest and during 30 min of intravenous infusion of L‐arginine (30g) or saline. We systematically administered L‐arginine, a precursor of nitric oxide, to examine the nitric oxide‐mediated regional cerebral vasomotor regulation. Compared to controls, patients with AH had similar resting CC (AH: 601±30 vs. Ctrl: 571±43 mL/min) and VA blood flow (AH: 109±11 vs. Ctrl: 105±11 mL/min). On administration of L‐arginine, the CC blood flow was similarly increased in both groups (AH: +11±4% vs. Ctrl: +13±3% at 25‐30 min). In contrast, increases in VA blood flow were blunted in AH patients (AH: +1±3% vs. Ctrl: +16±4% at 25‐30 min; P<0.05). BP decreased by ‐5±3% (P<0.05) in both groups during L‐arginine infusion. All variables returned near resting values after infusion. Blood flow and BP were unchanged during saline infusion. Our results indicate a diminished endothelial function within the brainstem circulation of patients with hypertension.

Grant Funding Source: Supported by CAPES, CNPq, FAPERJ.
Effects of antioxidants on cerebrovascular hemodynamics during moderate and high intensity exercise (1183.6)
Authors: Moralez Gilbert , White Daniel , Raven Peter
Published: June 2021

It has been identified that central reactive oxygen species (ROS) scavenge nitric oxide (NO) and increase central sympathetic nerve activity (SNA) outflow. During dynamic exercise increases in ROS have been measured across the brain. We tested the hypothesis that during dynamic leg cycling exercise, antioxidants would increase middle cerebral artery blood velocity (MCAv) and cerebrovascular conductance (CVCi). Five healthy subjects performed back supported semi‐recumbent dynamic leg cycling with antioxidant cocktail (AxT) and without AxT (placebo ‐ Pl). Arterial pressures (AP) and MCAv were measured continuously during moderate intensity dynamic leg exercise at heart rates (HR) of 120 bpm (e120) and heavy intensity at HR of 150 bpm (e150). No differences in AP were observed between Pl and Axt at e120 and e150 (P蠅0.50). MCAv during AxT at e120 and e150 was increased above Pl (P=0.06). However, the calculated CVCi was significantly greater at e120 and e150 between CT and Pl (P=0.05). From these data we conclude that Axt scavenged exercise induced central ROS resulting in increased central NO induced cerebrovascular vasodilation during exercise.
Oscillatory cerebral blood flow in postural tachycardia syndrome (1183.7)
Authors: Del Pozzi Andrew , Medow Marvin , Stewart Julian
Published: June 2021

Measureable upright cognitive loss occurs in postural tachycardia syndrome (POTS). Some POTS patients have impaired cognition associated with an excessive decrease in mean cerebral blood flow (CBF) equivalent to a loss of static autoregulation. More often, however, CBF is not decreased but a demonstrable loss of neurovascular coupling occurs and may result from time dependent changes in CBF. We tested the hypothesis that CBF changes comprise increased oscillatory CBF in POTS (N=10, age 17‐28 y) compared to healthy volunteers (N=9) by measuring changes in CBF velocity (CBFv) using transcranial Doppler ultrasound of the left middle cerebral artery during a 70° upright tilt. Total amplitude and peak power of heart rate, BP, and CBFv variability (V) were measured over an extended frequency range of 0.01 to 0.5 Hz using Welch’s method. Nonlinear methods were used to compute phase synchronization between MAP and CBFv. Upright HR was increased in POTS (128±7 vs 85±3 bpm), as was diastolic BP (74±3 vs 64±3 mmHg) Peripheral resistance, cardiac output, and mean CBFv were not different. Upright amplitude, peak power, and peak frequency of HRV were increased in POTS (p<.01) (11.1±1.2 centered at .088 Hz vs 7.6±1.1ms/Hz centered at 0.068Hz and 8.3±1.1 vs 4.2±0.7•!08ms2), as for BPV (p<.01) (9.2±0.8 vs 6.0±0.7mmHg/Hz centered at .086 Hz and 15.4±4.7 vs 3.0±1.1•!08mmHg2 centered at 0.70Hz), and for CBFV (pCBFv phase synchronization was much larger in POTS compared to control (P<.004) (0.97±0.01 vs 0.76±0.11).

When upright POTS patients have increased BP oscillations (Mayer) waves with disproportionately increased oscillations of CBFv occurring at a higher frequency than control. These observations cannot be interpreted within the framework of a linear Ohmic relationship between BP and CBF but rather indicate increased coupling of BP to CBFv in POTS when upright. Large oscillatory CBF has been shown to subvert neurovascular coupling in animal models.

Grant Funding Source: NHLBI
Methodological considerations for cerebrovascular reactivity testing and analysis (1184.3)
Authors: Inskip Jessica , Ravensbergen Rianne , O'Connor Shawn , Claydon Victoria
Published: June 2021

The cerebral microvasculature is exquisitely sensitive to carbon dioxide (CO2) and this cerebrovascular reactivity (CVR) is often used as a measure of cerebrovascular function. However, a review of the current literature reveals that the details of CVR protocols and analyses vary considerably between research groups. The objective of this study is to determine the sensitivity of CVR to these methodologies.

We used dynamic end‐tidal forcing to measure CVR to CO2 under conditions of controlled normoxia, hypoxia and hyperoxia. Low levels of end‐tidal CO2 were obtained by hyperventilation; high levels by hypoventilation with added inspired CO2. Supine blood pressure and middle cerebral artery blood flow velocity (MCAv) were continuously recorded, as were inspired and expired oxygen (O2) and CO2.

Here we discuss the physiological implications of different analysis techniques and also consider the effects on quantitative outcomes. We include the rationale and results of: different types of curve fitting; methods of normalizing MCAv; accounting for blood pressure changes; controlling O2; and introducing a phase lag between end‐tidal CO2 and MCAv.

It is difficult to know whether CVR results are widely generalizable, or reflect unique protocols or analyses. This work is intended to stimulate discussion and encourage the publication of transparent methods in an effort to improve research reproducibility.

Grant Funding Source: Supported by the Heart and Stroke Foundation of B.C. and Yukon (V.E.C.)