bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex differences in mouse aortic relaxation via estrogen receptor signaling (680.17)
Authors: Ansari Habib , Hamblin Milton
Published: June 2021

Cardiovascular disease is the leading cause of death both in the United States and worldwide. Estrogen receptors (ERs) have been previously shown to mediate the mechanisms responsible for playing cardioprotective roles. However, the effect of sex on estrogen receptor‐mediated vascular function is not well‐understood. We investigated the effect of the ER‐alpha agonist, PPT on phenylephrine (Phe; 10‐6 M)‐precontracted male and female mouse aortic rings in the presence and absence of the ER‐alpha antagonist, MPP, ERK1/2 inhibitor, PD98059, and +K‐ATP channel blocker, glibenclamide. We found that PPT induced aortic relaxation in both male and female endothelial‐intact mouse aortic rings at concentrations of 100 μM (62% ± 4 for males vs. 86.6% ± 5 for females) and 1000 μM (70% ± 6 for males vs. 99.9% ± 6 for females), respectively. However, in endothelium‐denuded mouse aortas, PPT‐induced relaxation was attenuated in both males and females, and there were no sex differences. MPP obviated PPT‐induced aortic relaxation (100 μM) in endothelial‐intact mouse aortas. Further, attenuated PPT‐induced aortic relaxation was observed when treated with PD98059 or glibenclamide in endothelial‐intact male and female aortas. In summary, we present potential sex differences in estrogen receptor‐mediated mechanisms for aortic relaxation involving ERK1/2 and the +K‐ATP channel.

Grant Funding Source: 5K12HD043451
The effect of experimental preeclampsia on cerebral blood flow autoregulation and cerebrovascular function (680.22)
Authors: Johnson Abbie , Chan Siu‐Lung , Moseley Janae , LaMarca Babbette , Cipolla Marilyn
Published: June 2021

This study investigated changes in CBFAR and vascular function in SD rats that were normal pregnant (NP; d20) or with experimental preeclampsia (ePE; d20). ePE was induced by combining placental ischemia and a high cholesterol diet. CBFAR was determined in vivo during acute infusion of phenylephrine to raise blood pressure and measurement of CBF using laser Doppler. The slope (m) of the pressure vs. CBF curves were compared between ePE (n=9) and NP (n=6). Myogenic responses were determined in isolated and pressurized posterior cerebral arteries (PCA; n=5/gr). mRNA expression of iNOS was determined using qPCR (n=5/gr). ePE caused hypertension (123 ± 4 vs. 111± 2 mmHg, p<0.05) and a 25% increase in plasma 8‐isoprostane (p<0.01 vs. NP), indicating oxidative stress. CBFAR was intact in 7/9 ePE rats and not different from NP rats (m=0.54±0.06 vs. 0.45±0.04; p>0.05). However, 2/9 ePE rats had impaired CBFAR (m=0.93±0.05; p<0.05 vs. NP). PCA from NP rats displayed myogenic activity and were smaller than passive diameters at 150 mmHg (149±17 vs. 210±13 μm; p<0.05). In contrast, the myogenic response was absent in PCA from ePE rats with no difference between active and passive diameters. mRNA expression of iNOS increased 2‐fold in PCA from ePE rats (p<0.01 vs. NP). Thus, CBFAR appears to be intact in the majority of ePE rats. The lack of a myogenic response in PCA from ePE animals may be due to oxidative stress and vascular inflammation.

Grant Funding Source: Supported by RO1 NS045940
Influence of age and ischemia on cardiac subsarcolemmal and interfibrillar mitochondria in a novel model of estrogen deficiency (680.6)
Authors: Garvin Alexandra , Aurigemma Nicole , Lehtihet Nadia , Hackenberger Jenna , Korzick Donna
Published: June 2021

Altered mitochondrial respiration (MR) and calcium retention capacity (CRC) are proposed cardiac cell death mechanisms exacerbated by aging in males. The present study aimed, for the first time, to determine changes in mitochondrial subpopulation function with age and ischemia/reperfusion (I/R) injury in the female heart. A novel model to recapitulate human menopause/age interactions was used in F344 female rats ovariectomized (OVX) at 15mo and studied at 24mo (n=15), vs adult (6mo; n=18). MR and CRC were assessed in isolated subsarcolemmal (SSM) and interfibrillar (IFM) mitochondria following in vivo coronary artery ligation (CAL; 31 min I and 10 min R) or sham. State 3 MR energized by either complex I (CI) or complex II (CII) substrates was selectively reduced by age in SSM (p<0.02), and by I/R in IFM (p<0.05). CRC was less in aged vs. adult IFM with I/R (38%), suggesting earlier mitochondrial permeability transition pore (MPTP) opening. At CI, but not CII, cyclosporine A (CsA) enhanced CRC in adult vs. aged (48%), suggesting reduced protective efficacy with age and MPTP involvement. In contrast to males, our data suggest a sex‐specific phenotype whereby reductions in both SSM and IFM dynamics may play an additive role in the enhanced susceptibility to I/R injury and myocardial infarction in the aged female heart, which remains the leading cause of death in older women.

Grant Funding Source: Supported by HL091097, AG044132.
Sex differences in the relationship between cerebral vascular resistance and sympathetic nerve activity: a magnetic resonance imaging study (680.9)
Authors: Hart Emma , Coope Tom , Warnert Esther , Harris Ashley , Stewart Lesley , Nightingale Angus , Wise Richard , Paton Julian
Published: June 2021

In men, we have found that cerebral vascular resistance (CVR) in the internal carotid (ICA), vertebral (VA) and basilar arteries (BA) is related to muscle sympathetic nerve activity (MSNA). Since sex hormones play a role in blood flow/pressure regulation, we hypothesised that CVR and blood flow in the ICA, VA, and BA would not be related to the level of MSNA or blood pressure (BP) in young women. In normotensive men (n= 11, age; 30 ± 2 yrs) and pre‐menopausal women (n=7; 33±2 yrs) blood flow in the ICA, VA and BA was measured using magnetic resonance phase contrast imaging at 2 locations (1 cm below/above the VA convergence) with concurrent brachial BP measurements. CVR was calculated as mean BP/blood flow. MSNA was similar in men and women (30 ± 1 vs. 28±1 bursts/100 hb) and positively related to CVR in the left and right ICA (r=0.74, r=0.62, P0.05). Interestingly, mean BP was negatively correlated with blood flow in the ICA, VA and BA in men (r=‐0.54, r=‐0.56, r=‐0.50, P<0.05), but not in women (P<0.05). In summary, men with high CVR and low blood flow in the intracranial arteries had higher MSNA and BP. Cerebral blood flow and CVR may be important in setting resting BP and MSNA in men but not in pre‐menopausal women. British Heart Foundation funded.

Grant Funding Source: Supported by the British Heart Foundation
Endogenous vascular endothelial growth factor tonically sustains myocardial performance and cardiac vagal baroreflex as revealed by Flk‐1 deficient mice (681.1)
Authors: Tsai Ching‐Yi , Chan Samuel H.H.
Published: June 2021

Whereas the role of vascular endothelial growth factor (VEGF) in vascular functions is well‐known, its action on heart functions is relatively wanting. In this study, we sought to demonstrate that endogenous VEGF tonically sustains myocardial performance and cardiac vagal baroreflex via Flk‐1. Echocardiography showed that compared to wild‐type mice, Flk‐1 deficient Kdr+/‐ mice exhibited significantly reduced ejection fraction and fraction shortening; alongside significant diurnal hypertension and tachycardia as revealed by radiotelemetry. 24‐h on‐line, real‐time power spectral analysis further showed significant decrease in heart rate variability and indices of spontaneous cardiac vagal baroreflex in Kdr+/‐ mice. Tractographic analysis based on MRI/DTI revealed that the robust functional connectivity between the nucleus tractus solitarii (NTS) and nucleus ambiguus was significantly decreased in Kdr+/‐ mice. Furthermore, the reduced myocardial performance and cardiac vagal baroreflex in Kdr+/‐ mice were exacerbated during neurogenic hypertension induced by i.c.v infusion of angiotensin II. We concluded that the endogenous VEGF sustains cardiac functions either by acting directly on Flk‐1 in the heart, or indirectly by affecting the cardiac vagal baroreflex via Flk‐1 in the NTS. This tonic modulatory mechanism is crucial to myocardial performance under neurogenic hypertension.
Aqueous extract of Acanthopanax divaricatus var. chiisanensis ameliorates blood pressure through a nitric oxide‐dependent mechanism: in vivo and in vitro studies (681.10)
Authors: Park Soo‐yeon , Do Gyeong‐Min , Shin Jae Ho , Kwon Oran
Published: June 2021

High blood pressure is one of the most important modifiable risk factors for cardiovascular disease. Many emerging evidence indicate that an array of plants might have a potential to regulate blood pressure by various mechanisms. In this study, we investigated the antihypertensive effects of Acanthopanax divaricatus var. chiisanensis (AE) and its active compound, Acanthoside‐D (AD), and also their underlying mechanisms on vascular actions in vivo and in vitro. Spontaneously hypertensive rats (n=10/group) were fed high‐cholesterol diet with AE or AD by gavage for 14 weeks, and their blood pressure was recorded weekly. Blood pressure was significantly reduced in the AE group compared to the control group. Consistent with this, we observed a significant reduction in arterial wall thickness by H&E staining and an activation of endothelial nitric oxide synthase by immuno‐fluorescence staining in the AE group. The findings in vivo were confirmed by increase of nitric oxide production and activation of PI3‐kinase‐Akt‐eNOS pathway in human umbilical vein endothelial cells after AE treatment. Taken together, the results provide a basis for the use of AE in regulating blood pressure by enhancing endothelial function in a nitric oxide‐dependent mechanism.

Grant Funding Source: Supported by MAF/FST Projects (S111111L010000) and MEST/Brain Korea 21 PLUS (22A20130012143).
Disrupted functional connectivity between brain stem nuclei in the neural circuit of cardiac vagal baroreflex of mice during neurogenic hypertension (681.2)
Authors: Chan Samuel H.H. , Tsai Ching‐Yi
Published: June 2021

Visualization of impairment of the cardiac vagal baroreflex, a clinical hallmark of hypertension, has never been materialized. We undertook this task using an experimental model of neurogenic hypertension that employed intracerebroventricular infusion of angiotensin II in male adult C57BL/6 mice. Based on tractographic evaluations using magnetic resonance imaging/diffusion tensor imaging of the medulla oblongata in the brain stem, we found that the connectivity between the nucleus tractus solitarii (NTS), the terminal site of baroreceptor afferents, and the nucleus ambiguus (NA), the origin of the vagus nerve, was disrupted in neurogenic hypertension, concurrent with impairment of the cardiac vagal baroreflex as detected by radiotelemetry. Intriguingly, we found that the disrupted NTS‐NA connectivity was reversible, and was related to oxidative stress induced by augmented levels of NADPH oxidase‐generated superoxide in the NTS. We conclude that depression of the cardiac vagal baroreflex induced by oxidative stress in the NTS in the context of neurogenic hypertension can be manifested in the form of dynamic alterations in the connectivity between the NTS and NA.
Inducible nitric oxide synthase blockade within the ventrolateral medulla differentially modulates the exercise pressor reflex in stroke rats (681.5)
Authors: Hoppenrath Andrew , Phillips Michael , Maher Timothy , Ally Ahmmed
Published: June 2021

We have previously shown that blockade of neuronal nitric oxide synthase (nNOS) within the rostral (RVLM) and caudal ventrolateral medulla (CVLM) differentially modulates cardiovascular responses via changes in glutamate and GABA concentrations during static skeletal muscle contraction. Using left‐sided stroked rats in this study, we determined if microdialyzing a specific iNOS antagonist into the left RVLM and/or the left CVLM would alter cardiovascular responses during static muscle contraction commonly known as the Exercise Pressor Reflex. Rats were stroked by employing a 90 minute left‐sided middle cerebral artery occlusion (MCAO) followed by 24 hours of reperfusion. In protocol 1, microdialysis of a selective iNOS antagonist, aminoguanidine (AGN; 10 µM) for 120 min into the left RVLM significantly attenuated cardiovascular responses during a static muscle contraction compared to those induced in intact rats. In Protocol 2, application of AGN into the left CVLM significantly potentiated the cardiovascular responses during muscle contractions. Finally, in Protocol 3, administration of AGN simultaneously into both the left RVLM and left CVLM produced results similar to those observed with Protocol 1. These results demonstrate that blockade of iNOS within the two regions of the ventrolateral medulla differentially modulates cardiovascular responses during static exercise in stroked rats.
Blockade of transient receptor vanilloid channels prevents the sympathoexcitatory response to central NaCl infusion (683.3)
Authors: Simmonds Sarah , Stocker Sean
Published: June 2021

Increased cerebrospinal fluid sodium concentration elevates sympathetic nerve activity (SNA) and arterial blood pressure (ABP) in salt‐sensitive hypertension. Recent in vitro evidence suggests the brain senses changes in osmotic pressure through TRPV1 channels. The present study investigated whether the sympathoexcitatory response to increased cerebrospinal fluid NaCl was mediated by central TRPV1 channels. Male Sprague‐Dawley rats were anesthetized with Inactin and instrumented with a lateral intracerebroventricular (ICV) cannula. ICV infusion of 1M NaCl (n=8) significantly increased lumbar SNA (140±12%), heart rate (20±7bpm), and mean ABP (9±1mmHg). ICV pretreatment with the broad‐spectrum TRPV channel blocker ruthenium red (5mM, 2uL, n=8) eliminated the sympathoexcitatory response to ICV 1M NaCl: lumbar SNA (106±5%), heart rate (‐6±7bpm), and mean ABP (1±2mmHg). Similarly, ICV pretreatment with the selective TRPV1 channel antagonist SB366791 (3mM, 2uL, n=4) prevented any change in lumbar SNA (106±3%), heart rate (4±6), and mean ABP (1±1mmHg). ICV injection of ruthenium red or SB366791 did not alter any variable. These findings suggest that central TRPV1 channels mediate the sympathoexcitatory response to acute increases in cerebrospinal fluid NaCl concentration.

Grant Funding Source: Supported by NIH R01HL113270 and AHA Established Investigator Award
Olfactory hallucinations are inhibited by increasing brain gamma‐aminobutyric acid levels (684.8)
Authors: Henkin Robert
Published: June 2021

Olfactory hallucinations without associated myoclonic activity are obnoxious, horrible sensations which occur in the nasal cavity without any external stimulation and are labeled phantosmias. They are so pervasive and persistent that they can permeate the entire being like a persistent, unremitting pain. They are of two types: unirhinal (in one nostril) and birhinal (in both nostrils). Unirhinal phantosmias occur spontaneously, mainly in women, are uncommon but cyclic in nature, are exacerbated by laughing or shouting, have associated EEG abnormalities and are inhibited by Valsalva maneuvers or CO2 inhalation. Birhinal phantosmias occur commonly following loss of smell (hyposmia), occur equally in men and women, are persistent not cyclic, have few associated EEG abnormalities and are unchanged by physiological maneuvers. Functional magnetic brain imaging revealed massive activation in prefrontal cortex to perception of these phantosmias. Magnetic resonance spectroscopy revealed lower than normal levels of GABA in these brain regions. Treatment with GABAergic drugs or transcranial magnetic stimulation increased brain GABA levels and inhibited these phantosmias. These studies indicate inhibition of brain GABA can initiate phantosmias, as occurs in phantom limb, by activating normally inhibited brain pathways which are activated either spontaneously, by stimulation of peripheral olfactory pathways or following hyposmia but are inhibited by increasing brain GABA levels.
Alterations in 5‐HT and glutamate release in the rat NTS in heart failure (686.10)
Authors: Hosford Patrick , Mastitskaya Svetlana , Gourine Alexander , Ramage Andrew
Published: June 2021

In man and in animal models of early heart failure the baroreflex and the cardiopulmonary reflex have been reported to be impaired. Glutamate and 5‐HT are released in the nucleus tractus solitarius (NTS) by cardiovascular afferent activation (see Ramage & Villalón, 2008, TIPS 29:472‐481). The present study was designed to determine if the release of these transmitters in real time is altered in the rat permanent‐occlusion heart failure model. 5‐HT was measured via a carbon fibre electrode using a modified form of fast differential voltammetry, while glutamate was measured using a glutamate biosensor (Sarissaprobes®). Rats, with heart failure or sham operated were anaesthetized with α‐chloralose (120 mg/kg; i.v), neuromuscular blocked and artificially ventilated. Activation of cardiopulmonary afferents by phenylbiguanide (PBG; i.a.) caused a significant (P< 0.05; n=4) increase in 5‐HT to 29 ± 6nM in heart failure compared to 10 ± 0.4nM in sham operated rats. PBG evoked a significantly smaller hypotension in heart failure (34 ± 5mmHg) compared to that of sham (58 ± 6 mmHg) rats. However, PBG evoked bradycardia was not significantly different, 148 ± 39 compared to 191 ± 12 bpm in sham rats. Activation of the depressor reflex by i.v. injection of phenylephrine (3μg per animal) caused a significantly greater increase in glutamate in heart failure (1.6 ± 0.2μM; n=3) compared to sham (0.6 ± 0.2μM, n=3) rats. The cardiovascular effects were not significantly different. In conclusion this preliminary data suggests that in heart failure afferent activation increases the release of these two transmitters in nucleus tractus solitarius (NTS). The consequence of this in the development of heart failure remains to be determined.
Focal hemorrhagic stroke in the left or right rat posterior insular cortex results in equipotent changes in sympathetic activity (686.11)
Authors: Marins Fernanda , D’Abreu Bárbara , Limborço‐Filho Marcelo , Fontes Marco Antonio
Published: June 2021

Evidence suggests that unilateral damage to the insular cortex(IC) leads to autonomic imbalance and cardiovascular (CV) dysfunction. We evaluated the CV effects from focal hemorrhage (ICH) into the left (L) or right (R) IC. Wistar rats were anesthetized for microinjection of autologous arterial blood (ICH) or saline (200nL, n=10 each side/group) into the L or R IC (0mm AP/ ±5.8mm LL/ 7mm DV). After 24 hours, mean arterial pressure (MAP) and heart rate (HR) were measured in awake condition. Then, ICH and control group (n=7 each side) were anesthetized and renal sympathetic activity (RSNA) was record. ICH increased baseline HR (Δ:L‐ICH 471±8 vs saline 407±7bpm; R‐ICH 465±8 vs saline 408±5bpm, P<0.05) without changing MAP. HR was restored to baseline levels after i.v. atenolol injection (2mg/kg). Strikingly, ICH rats presented a reduced baseline RSNA (Δ:L‐ICH 112±5 vs saline 148±7spikes/sec; R‐ICH 121±4 vs saline 149±10spikes/sec, P<0.05). There were no differences between L‐ and R‐ICH. We conclude that focal stroke into posterior IC can alter the cardiac and renal autonomic control without lateral predominance. These findings can help to understand the cardiac and renal dysfunctions observed after cortical damage.

Grant Funding Source: CNPq, Fapemig, Capes and INCT NanoBioFar
Repetitive electroacupuncture attenuates cold‐induced hypertension is associated with opioid precursors in hypothalamic paraventricular and arcuate nuclei (686.2)
Authors: Li Min , Tjen‐A‐Looi Stephanie , Longhurst John
Published: June 2021

Acupuncture lowers elevated blood pressure in clinical and experimental hypertension, possibly through an opioid mechanism. To mimic human studies, we performed repeated electroacupuncture (EA) on unanesthetized male SD rats exposed to cold (5°C) for 11 weeks. Systolic blood pressures (SBP) were measured weekly. Rats were randomly divided into EA (n=9), sham (n=6) and untreated hypertension groups (n=6) after 6 weeks of cold exposure when elevated SBP had stabilized. EA and sham groups then received either repetitive EA (1‐4 mA, 2 Hz, 0.5 ms) at ST36‐37 acupoints bilaterally (overlying deep peroneal nerve) or sham (needle placement without electrical stimulation) 30 min twice weekly for 5 weeks. The elevated SBP in the EA group was reduced after 6 sessions and remained low throughout treatment (139 ± 3 vs. 175 ± 3 mmHg, EA vs. sham) and 72 hr after termination of EA (155 ± 4 vs. 187 ± 3 mmHg, after EA vs. sham). Both preproenkephalin (PPE) and proopiomelanocortin (POMC) mRNA in PVN 72 hr after EA were increased in the EA (0.43±0.001 and 85±1.2, respectively) compared to the sham group (0.30±0.001 and 44±1.1) and the untreated hypertensive rats (0.31±0.012 and 42±1.2). POMC mRNA also was increased in the arcuate nucleus of the EA group (100± 3.2 vs. 82± 3.8, EA vs. sham). Thus, prolonged inhibition of elevated blood pressure by action of EA is associated with prolonged increases of opioid mRNA expression in the PVN and ARC.

Grant Funding Source: Supported by NIH HL‐63313 and HL‐072125
Superoxide depression in the rostral ventrolateral medulla contributes to centrally antihypertensive action of moxonidine (686.31)
Authors: Wang Weizhong , Wang Yangkai , Yu Qiang
Published: June 2021

Centrally antihypertensive action of moxonidine has been demonstrated to be resulted from activation of Imidazoline‐1 receptor (I1R) in the rostral ventrolateral medulla (RVLM). Angiotensin II (Ang II)‐derived superoxide is a major contributor to high level of blood pressure and sympathetic outflow in hypertension. The objective of the present study was to determine the effect of moxonidine on the Ang II‐derived superoxide in the RVLM of spontaneously hypertensive rat (SHR). Intracerebroventricular infusion of moxonidine (20 nmol/day, 2 wk) produced a significant decrease in blood pressure (152±4 vs 183±5 mmHg) in SHR, which can be prevented by the I1R antagonist efaroxan but not the alpha2 receptor antagonist yohimbine. Chronic treatment with moxonidine decreased the protein expression of Ang II receptor type 1 (AT1R) and NADPHase (NOX4) in the RVLM, but also blunted the cardiovascular response to microinjection of Ang II (10 pmol) into the RVLM. Production of superoxide in the RVLM was also reduced in the SHR following 2‐wk treatment with moxonidine. Moreover, it was found that subunit p50 of Nuclear Factor Kappa B (NFkB) was significantly reduced and IkB was increased in the moxonidine‐treated SHR. It is concluded that a decrease in Ang II‐AT1R‐supreoxide via NFkB pathway contributes to centrally antihypertensive action of moxonidine. This work was supported by NSFC (81170240 and 81370363).
Functional studies of rostral ventrolateral medulla neurons using manganese‐enhanced magnetic resonance imaging in sedentary versus physically active rats (686.36)
Authors: Ingles Judith , Huereca Daniel , Holt Avril , Mueller Patrick
Published: June 2021

A sedentary lifestyle, a key risk factor in cardiovascular disease (CVD), is linked to increased sympathetic nerve activity (SNA). Control of SNA occurs via bulbospinal catecholaminergic (C1) and non‐C1 neurons primarily in the RVLM. We recently reported that sedentary, but not physically active rats, exhibit increased dendritic branching in bulbospinal C1 RVLM neurons in a specific caudal to rostral pattern. However, regionally specific increases in RVLM neuronal activation have not yet been associated with increased dendritic branching. In many brain regions, manganese (Mn2+), a paramagnetic ion, has been used as a contrast agent to detect neuronal activity via calcium channel uptake. The purpose of this study was to develop MeMRI for in vivo studies of the RVLM, with the hypothesis that sedentary rats would have increased RVLM neuronal activity and greater Mn2+ uptake. One sedentary and one active rat (12 wks wheel running) were administered Mn2+ chloride (66mg/kg, IP), and a control rat was given saline. After 24 hours, rats were imaged (7T, Bruker Avance) and saline values were subtracted from Mn2+ injected animals. Uptake of Mn2+ in the RVLM was greater in the sedentary versus active rat (e.g. 808 vs. 327 avg voxel intensity, respectively). Notably, only the sedentary rat had a pattern of increased uptake in the caudal to rostral RVLM, very similar to our structural studies. These preliminary studies suggest that increased dendritic branching in more rostral RVLM neurons may account for enhanced RVLM neuronal activity and the growing prevalence of CVD in sedentary individuals.

Grant Funding Source: Supported by HL096787‐PJM; VA 1l01RX001095‐01‐AGH
Physical (in)activity‐induced changes in tonic excitation and inhibition in the rostral ventrolateral medulla (686.37)
Authors: Laws Maxwell , Mischel Nicholas , Mueller Patrick
Published: June 2021

The RVLM contains neurons that regulate blood pressure and exhibit (in)activity‐dependent neuroplasticity. Previous studies have found that sedentary animals have enhanced responses to direct activation of RVLM neurons that regulate sympathetic nervous activity (SNA). We hypothesized that sedentary animals have heightened sympathoexcitation due to enhanced glutamatergic and/or attenuated GABAergic neurotransmission. Rats were housed with or without running wheels for 12 weeks and were then anesthetized with Inactin and instrumented to record mean arterial pressure, heart rate, and splanchnic SNA during microinjections into the RVLM. The RVLM was functionally identified by a pressor response to glutamate (30 nl, 100 mM). Bilateral blockade of GABAA receptors with bicuculline (5mM) was performed either alone or following bilateral injection of the ionotropic glutamate receptor antagonist kynurenic acid (40 mM). Sedentary versus active rats displayed a greater SNA response following bicuculline injection alone (Δ62±7% v Δ38±8%, p<0.05). The SNA response to bicuculline after injection of kynurenate was attenuated in sedentary rats (Δ62%±7 v Δ 26%±4, p<0.05). Active rats did not show a significant SNA attenuation (Δ38±8% v Δ31±6%, p>0.05). These findings suggest that the exaggerated SNA increase in sedentary versus physically active rats following GABAA blockade is mediated by enhanced activation of ionotropic glutamate receptors. This study further demonstrates (in)activity‐dependent alterations in the RVLM and these changes may contribute to an increased risk for cardiovascular disease in sedentary individuals.

Grant Funding Source: Supported by R01‐HL096787
Differential cardiovascular responses elicited by point‐specific acupuncture during phenylbiguanide‐induced reflex stimulation (686.4)
Authors: Tjen‐A‐Looi Stephanie , Cheng Ling , Li Peng , Longhurst John
Published: June 2021

Stimulation of cardiopulmonary receptors with phenylbiguanide (PBG) consequent to vagal activation decreases blood pressure (BP) and heart rate (HR) mediated by the nucleus ambiguus (NA) and nucleus tractus solitarii (NTS). EA at P5‐6 reverses PBG‐induced reflex bradycardia through modulatory actions in the NA. The current study examined effects of EA at P5‐6 (median nerves), ST36‐37 (deep peroneal nerve), LI4‐L7 (branches of median and superficial radial nerves) and G37‐39 (superficial peroneal nerve) acupoints on the PBG reflexes in the NTS. We hypothesized that point specific EA modulation of PBG‐induced vasodepression and bradycardia is related to differential levels of EA‐related somatic and cutaneous afferent evoked activity in cardiovascular and EA‐sensitive NTS neurons. NTS activity and HR and BP responses were recorded every 10 min during either repeated stimulation of the cervical vagus or iv PBG in cats. After two consistent responses, 30 min EA was applied bilaterally at P5‐6, ST36‐37, LI4‐L7 or G37‐39. NTS neurons displayed cardiac rhythmicity, convergence from vagal and baroreceptor afferents, and nerves located under acupoints. Kainic acid into the medial NTS decreased bradycardia from ‐40±10 to ‐18±2 b/m and depressor from ‐32±6 to ‐20±2 mmHg. EA at P5‐6 reduced for over 60 min the depressor by 67% and bradycardia by 60%. Unlike LI4‐L7 and G37‐39, EA at ST36‐37 reduced the depressor by 56% and the bradycardia by 60%. Brief activation of median and deep peroneal nerves showed much greater NTS evoked activity, compared to cutaneous nerves. Unlike LI4‐L7 and G37‐39, EA at P5‐6 and ST 36‐37 reduced vagal evoked NTS activity from 12±2.0 to 2±0.8 and 11.5±1.3 to 2±1.2 spikes/30stim, respectively. Thus at the different acupoints, brief stimulation differentially activates cardiovascular NTS neurons and following 30 min EA elicits point specific responses to PBG stimulation. These data support point specific EA responses that reverse cardiovascular inhibitory reflex responses.

Grant Funding Source: HL‐72125, HL‐63313
Melanocortin‐4 receptors in the PVN and RVLM are important in mediating cardiovascular responses to acute stress (686.7)
Authors: do Carmo Jussara , Sessums Price , Ebaady Sabira , Freeman John , Hall John , Silva Alexandre
Published: June 2021

Our previous studies demonstrate an important role for the brain melanocortin system in regulating sympathetic nervous system activity and blood pressure (BP) as well as in modulating BP responses to stress. However, the brain regions involved in melanocortin‐4 receptors (MC4R)‐mediated modulation of cardiovascular responses to acute stress are unknown. In this study, we examined whether rescue of MC4R specifically in the paraventricular nucleus of the hypothalamus (PVN) or in the rostral ventrolateral medulla (RVLM) of whole‐body MC4R deficient mice (LoxTB‐MC4R mice) restores BP response to acute air‐jet stress. Using Cre‐loxP technology we selectively rescued MC4R in the PVN (LoxTB‐MC4R/Sim1, n=5) or RVLM (Cre‐RVLM/LoxTB‐MC4R mice, n=5). Mice were implanted with telemetry probes for measurement of mean arterial pressure (MAP). After a 10‐day recovery period, baseline MAP was measured for 3 consecutive days and during an acute air‐jet stress test. MAP was continuously measured for 30 minutes before, during and 30 minutes after the stress test. LoxTB‐MC4R mice were slightly heavier (53±2 vs 43±1 and 48±3 g), but had similar baseline MAP (109±1 vs 110±1 and 113±2 mmHg) compared to LoxTB‐MC4R/Sim1 and Cre‐RVLM/LoxTB‐MC4R mice. Acute air‐jet stress significantly increased MAP by 28±2 and 33±2 mmHg in loxTB‐MC4R/Sim1 and Cre‐RVLM/LoxTB‐MC4R compared to only 22±2 mmHg in loxTB‐MC4R mice. These results indicate that MC4Rs in PVN and RVLM neurons participate in the modulation of BP response to acute stress. (NHLBI‐PO1HL51971, NIGMS P20GM104357 and AHA SDG5680016)

Grant Funding Source: AHA and NIH
High fat feeding in mice is insufficient to induce cardiac dysfunction and does not exacerbate heart failure (688.11)
Authors: DeMartino Angelica , Brainard Robert , Watson Lewis , Brittian Kenneth , Readnower Ryan , Boakye Adjoa , Zhang Deqing , Hoetker Joseph , Bhatnagar Aruni , Baba Shahid , Jones Steven
Published: June 2021

Feeding high fat diet (HFD) to mice is a commonly used model to investigate the impact of risk factors on cardiovascular physiology and the development of disease. Therefore, we sought to investigate whether a high fat diet (HFD) alone could produce cardiac dysfunction. Mice were fed a normal chow diet, a milk‐based HFD (60% cal from fat), or a lard‐based HFD (60% cal from fat) for a period of 28 weeks. Neither anesthetized (at 18 weeks) nor conscious echocardiography (28 weeks) revealed any evidence of cardiac dysfunction, despite elevated body fat in the two HFD groups. We next evaluated whether a HFD would exacerbate cardiac dysfunction during heart failure. Mice fed a HFD were subjected to myocardial infarction but experienced no more significant ventricular dysfunction than normal diet fed mice. These largely negative results compelled us to investigate a more severe model of hyperglycemia/obesity. Next, db/db mice were subjected to myocardial ischemia‐reperfusion and demonstrated a significant reduction in fractional shortening compared to wild‐type (WT) littermates. Interestingly, when subjected to pressure overload, db/db mice did not exhibit more severe dysfunction than WT littermates. In conclusion, our findings, coupled with several similar reports from other groups, indicate that a HFD may not reliably replicate the pathophysiological impact of a western diet on the murine heart.

Grant Funding Source: Supported by the NIH and AHA
Regional variation in the secretory function of visceral fat depots from severely obese women (688.4)
Authors: Mauriege Pascale , Joanisse Denis , Cartier Amelie , Lemieux Isabelle , Bergeron Jean , Biron Simon , Marceau Picard , Richard Denis
Published: June 2021

Because of its hepatic venous drainage, visceral fat accumulation is an important risk factor for obesity‐related metabolic complications. Objective: To examine the secretory function of a properitoneal fat, the round ligament (RL) in severely obese women. Methods: Metabolic biomarkers, adipogenic, pro‐ vs. anti‐inflammatory, and prothrombotic characteristics were assessed in the RL adipose tissue (AT), and compared to visceral depots, the omental (OME) and mesenteric (MES) fat, in forty‐eight severely obese women (BMI, 54 ± 11 kg/m2), aged 38 ± 9 yrs. Expression of key enzymes involved in lipid metabolism (lipoprotein lipase, LPL; hormone‐sensitive lipase, HSL and phosphodiesterase‐3B, PDE‐3B), and of adipogenic factors (peroxisome proliferator activated receptors‐γ1/2, PPAR‐γ1/2) was measured by real‐time PCR. AT mRNA levels of plasminogen activator inhibitor‐1 (PAI‐1), interleukin‐6 (IL‐6), tumor necrosis factor‐α (TNF‐α) and adiponectin were also determined. Results: AT‐LPL mRNA levels were the highest in the RL depot (0.005<p<0.05), whereas HSL expression did not show regional variation. The highest PDE‐3B and lowest PAI‐1 mRNA levels were observed in the RL and MES fat (0.0001p<0.05). The lowest IL‐6 and TNF‐α as well as the highest adiponectin and PPAR‐γ1/2 mRNA levels were found in the RL AT (0.0001<p<0.05). Conclusion: Despite its anatomic location in the intraabdominal cavity, RL should not be considered as a “classical” visceral AT, as some of its secretory characteristics may contribute to limit the deleterious impact of visceral fat.

Grant Funding Source: Supported by the CIHR and CRIUCPQ
CD11c positive cells are prevalent in perivascular adipose tissues of type 2 diabetic mice rather than in the vascular wall (688.7)
Authors: Qiu Tianyi , Li Min , Miles Tanner , Hill Michael
Published: June 2021

Type 2 diabetes is associated with chronic systemic inflammation and the recruitment of immune cells. In this study, we postulated that CD11c positive cells, a specific subset of lymphocytes, are increasingly expressed with age in perivascular adipose tissues from diabetic mice. Homozygous Type 2 diabetic (db/db) and heterozygous control (DbHET) mice from the same strain were purchased from Jackson Laboratory, and divided into four age groups: 6‐10, 12‐16, 18‐22, and greater than 24 weeks. Epididymal (EAT), mesenteric (MAT), pericardial (PCAT), and periaortic (PAAT) adipose tissues were collected from the db/db and DbHET mice along with spleen, thoracic aortas (TA), mesenteric (MA), and left anterior descending coronary (LAD) arteries. All samples were used to detect CD11c m RNA level using quantitative real‐time PCR. Our data show an age‐dependent increase in CD11c expression of EAT, MAT, PCAT and PAAT adipose tissues from db/db mice. In contrast, CD11c expression remained constant among all four age groups of DbHET mice. Within each age group, higher adipose tissue CD11c levels were observed in db/db mice, compared to those of the DbHET mice. No significant changes of CD11c expression were detected in spleen, TA, MA or LAD. Overall, our data support the conclusion that in a mouse model of Type 2 diabetes, CD11c positive cells accumulate in a duration of diabetes‐dependent manner in the perivascular adipose tissues, rather than in the vascular wall. The impact of these cells on vascular function therefore likely occurs through paracrine regulated mechanisms.

Grant Funding Source: NIH HL085119
Garlic attenuate hypertension and renal clearance in streptozotocin‐diabetic rats: a possible role of plasma and kidney angiotensin converting enzyme 1 (689.1)
Authors: Al‐Qattan Khaled , Thomson Martha , Ali Muslim , Mansour Mohamed , J Divya
Published: June 2021

Objective: The effect of garlic on the blood pressure and renal clearance in relation to plasma and kidney angiotensin converting enzyme 1 (ACE‐1) concentration in conscious early streptozotocin‐diabetic rats was investigated. Method: Normal rats (n=10) received 0.5 ml normal saline (NR/NS), diabetic rats (n=10) received 0.5 ml NS (DR/NS) and diabetic rat (n=10) received 500 mg/ml/kg garlic extract (DR/GE) as daily intraperitoneal injections for eight weeks. Results: After treatment, NR/NS, DR/NS & DR/GE: blood glucose = 8.1±0.4, 26.7±0.8a & 12.4±0.2a,b mmol/l; serum insulin = 1.12±0.09, 0.12±0.02a & 0.52±0.04a,b ng/ml; blood pressure = 105±2, 175±3a & 155±2a,b mmHg; water intake = 29±1, 190±2a & 175±1a,b ml/24 h; urine output = 8±1, 93±1a & 79±1a,b ml/24 h; plasma ACE‐1 = 550±7, 755±10a & 689±8a,b pg/ml, kidney ACE‐1 = 1917±3, 1003±6a & 1646±5a,b pg/mg protein; serum albumin = 1.93±0.01, 0.86±0.03a & 1.34±0.04a,b g/dl; urine albumin = 0.017±0.001, 0.042±0.001a & 0.013±0.001a,b g/dl; serum creatinine = 83±2, 117±a & 91±2a,b µmole/l; urine creatinine = 1.3±0.06, 13.0±1.0a & 7.4±0.71a,b mmol/24 h, respectively. a: sig. different compared to NR/NS, b: sig. different compared to DR/Ns. Conclusion: Garlic may attenuate changes in diabetic blood pressure and renal clearance partially by minimizing changes in systemic and kidney ACE‐1 concentrations.

Grant Funding Source: KU #SL09/10
Diabetic renal injury is not prevented or reduced by increasing renal arginine availability (689.11)
Authors: Awad Alaa , You Hanning , Gao Ting , Cooper Timothy , Morris Sidney
Published: June 2021

Our recent publication showed that pharmacological blockade of arginases confers kidney protection in diabetic nephropathy via a nitric oxide synthase 3 (NOS3)‐dependent mechanism. Arginases compete with NOS for the common substrate L‐arginine. L‐arginine or L‐citrulline supplementation showed beneficial effect in patients with hypertension, angina and erectile dysfunction by improving endothelial function with enhanced NO synthesis. Therefore, we hypothesized that L‐arginine or L‐citrulline supplementation would prevent or reduce diabetic renal complication.

DBA mice injected with multiple low doses of vehicle or streptozotocin (STZ; 50 mg/kg ip for 5 days) were provided drinking water (DW) supplemented with L‐arginine, L‐citrulline, isonitrogenous nonessential amino acid control or no amino acids (DW control) for 9 weeks.

Diabetic mice with DW control showed significant increases in urine albumin excretion (p<0.05), albumin/creatinine ratio (p<0.05), kidney weight/body weight ratio (p<0.05), plasma creatinine (p<0.05), blood urea nitrogen (p<0.05), glomerular histopathological changes (p<0.001), kidney macrophage recruitment (p<0.001), kidney arginase activity (p<0.05), kidney argnase‐2 protein expression (p<0.05), kidney TNFα (p<0.01) and fibronectin (p<0.01) mRNA expression compared to normal mice after 9 weeks of diabetes. Isonitrogenous amino acid supplementation in diabetic mice was similar to DW control diabetic mice. Interestingly, neither L‐arginine nor L‐citrulline supplementation in diabetic mice affected any of these renal parameters despite increasing kidney arginine levels (6‐ and 8‐fold; respectively).

These findings indicate that chronic L‐arginase or L‐citrulline supplementation does not prevent or reduce diabetic renal injury.

Grant Funding Source: Supported by NIH R01 DK094930
L‐citrulline, but not L‐arginine, prevents diabetes‐induced glomerular hyperfiltration and proteinuria (689.12)
Authors: Persson Patrik , Fasching Angelica , Teerlink Tom , Hansell Peter , Palm Fredrik
Published: June 2021

Diabetes is associated with increased production of reactive oxygen species leading to decreased nitric oxide (NO) bioavailability and intrarenal hypoxia. Plasma L‐arginine concentration, the substrate for NO synthesis, is reduced in diabetes and we therefore hypothesis that L‐arginine or L‐citrulline supplementation improve NO production and thereby protects kidney function in diabetes. Glomerular filtration rate (GFR), total renal blood flow (RBF), in vivo oxygen consumption (QO2), cortical oxygen tension (PO2) and urinary protein excretion were evaluated in control and streptozotocin‐diabetic male Sprague‐Dawley rats with and without chronic L‐arginine or L‐citrulline supplementation (1‐2 g/day) in the drinking water for the 21‐day duration of diabetes. GFR was increased in untreated (2.6±0.2 ml/min/kidney) and L‐arginine treated diabetics (2.3±0.2 ml/min/kidney) compared to controls (1.2 ml/min/kidney). However, L‐citrulline administration to diabetics prevented the glomerular hyperfiltration (1.4±0.1 ml/min/kidney). RBF was not affected by diabetes or any of the treatments, resulting in increased calculated filtration fraction (FF) in untreated diabetics compared to controls (0.39±0.04 vs. 0.27±0.02), which was prevented by L‐citrulline treatment to diabetics (0.25±0.04). The increased urinary protein excretion in untreated diabetics (142±25 vs 75±7 µg/min/kidney) was also prevented by L‐citrulline treatment (67±7 µg/min/kidney). The diabetes‐induced intrarenal tissue hypoxia, resulting from increased QO2, was unaffected by any of the treatments. In conclusion, L‐citrulline, but not L‐arginine, supplementation prevents diabetes‐induced glomerular hyperfiltration by reducing the FF, which also prevents the increased urinary protein excretion commonly associated with the progression of diabetic nephropathy.
Hepatocyte nuclear factor 4α negatively regulates STIM1 protein expression in human glomerular mesangial cells (689.15)
Authors: Wang Yanxia , Wu Peiwen , Chaudhari Sarika , Ma Rong
Published: June 2021

Store‐operated Ca2+ signaling pathway plays an important role in physiological and pathological processes in glomerular mesangial cells. STIM1 is a key component of this Ca2+ entry pathway. We have recently demonstrated that high glucose (HG) significantly increased the expression level of STIM1 protein in cultured human mesangial cells (HMCs). However, the underlying mechanism for the HG response is unknown. Hepatocyte nuclear factor 4α (HNF4α) is a nuclear receptor expressed mainly in the kidney and liver, and regulates transcription of many genes. The present study was carried out to determine if HNF4α regulated STIM1 expression in response to HG treatment in HMCs. In cultured HMCs, HG treatment (25 mM for 6 days) significantly inhibited HNF4α‐DNA binding determined by electrophoretic mobility shift assay. Chromatin immunoprecipitation assays showed that HNF4α binding to STIM1 promoter region was attenuated by HG treatment. Knockdown of HNF4α using siRNA increased STIM1 mRNA and protein expressions. Furthermore, inhibition of store‐operated Ca2+ entry or knockdown of STIM1 increased fibronectin and collagen IV protein expressions in HMCs. Knockdown of HNF4α decreased the expression levels of both fibronectin and collagen IV proteins. These results suggest that HNF4α represses STIM1 transcription in HMCs.

Grant Funding Source: NIH/NIDDK
Effects of hyperglycemia and cyclic stretching on MMP‐2 and TGF‐β in rat mesangial cells (689.8)
Authors: White Tiffani , Spires Denisha , Roman Richard , Williams Jan
Published: June 2021

Previous studies have demonstrated that matrix metalloproteinase‐2 (MMP‐2) is involved in cleaving and activating several non‐extracellular matrix substrates as well such as transforming growth factor‐beta (TGF‐β) that participate in the accumulation of mesanigal extracellular matrix leading to glomerulosclerosis during diabetes‐induced renal disease. However, the mechanism by which MMP‐2 becomes activated remains unclear. Therefore, the aim of the present study was to compare the effects of hyperglycemia and cyclic stretching (FlexCell System) on the expression of MMP‐2 and TGF‐β in cultured rat mesangial cells (MCs). MCs were seeded on 6‐well flex‐bottom plates and cultured in normal glucose (NG) medium. After 24 hrs, the wells in each plate were equally divided into NG and high glucose (HG). The next day, MCs were exposed to cyclic stretching for 18 hrs. We did not observe any differences in MMP‐2 and TGF‐β expression between static NG‐ and HG‐treated MCs. However, exposure to cyclic stretching significantly increased the expression of MMP‐2 and TGF‐β protein in both NG and HG‐treated MCs in comparison to static‐treated MCs. Moreover, MMP‐2 activity was markedly increased in response to cyclic stretching regardless of whether hyperglycemia was present. These data indicate that the upregulation of MMP‐2 and TGF‐β in MCs is primarily due to cyclic stretching rather than hyperglycemia.
Expression of amphiregulin in various models of polycystic kidney disease (690.1)
Authors: Bunni Marlene , Steele Stacy , Bell P Darwin
Published: June 2021

In polycystic kidney disease (PKD) there is the continual expansion of cysts throughout the time course of this disease. The mechanisms that control the rate of cystic growth are not fully known. In PKD, the epidermal growth factor (EGF) receptor is mislocalized to the apical membrane of epithelial cells that line cystic structures. The findings that cystic fluid contains various hormones and signaling molecules further suggests that growth factors may play a role in regulation of cystic growth. The purpose of this study was to determine which EGF receptor dependent growth factors are elevated in PKD. Growth factors from human cystic fluid and mouse models of PKD were measured with an Elisa assay and RT‐PCR. Amphiregulin (Areg), epiregulin (Ereg), transforming growth factor alpha (TGFα), heparin binding EGF (HBegf) and egf were measured. In the IFT88 knockout mouse model where cilia are deleted, there was a four‐fold increase in Areg mRNA expression in mice that lacked cilia compared to mice with cilia. All other growth factors were the same between cilia minus versus cilia plus mice. In mice with a knockout of polycystin 2 there was a 5 fold increase in only Areg compared to mice with polycystin 2. In mice that lacked polycystin 1 there was 3 fold increase in Areg and an 8 fold increase in Ereg. Other growth factors were unchanged by the presence or absence of these proteins that cause autosomal dominant PKD (ADPKD). In fluid collected from individual cysts from human ADPKD kidneys we found that Areg concentration varied between 49 to 250 pg\ml and also varied between cysts from the same kidney. These results suggest that Areg and possibility Ereg may play a role in cystogenesis in PKD.

Grant Funding Source: P30DK074038 and VA Merit
Hypoxia inducible factor‐1α mediates the profibrotic action of albumin in renal tubular cells (690.12)
Authors: Hu Junping , Zhu Qing , Han Weiqing , Li Xiaoxue , Li Pin‐Lan , Li Ningjun
Published: June 2021

Proteinuria is closely associated with the progression of chronic kidney diseases (CKD) by producing renal tubulointerstitial fibrosis. Over‐activation of hypoxia inducible factor (HIF)‐1α has also been implicated in the progression of CKD. The present study tested whether HIF‐1α mediated albumin‐induced profibrotic action in cultured rat renal proximal tubular cells. Western blot assay showed that incubation of the cells with albumin (20 μg/ml) for 48 hrs significantly increased HIF‐1α protein level by 2.26 ± 0.33 fold, collagen‐I by 2.13 ± 0.037 fold and tissue inhibitor of metalloproteinase (TIMP)‐1 by 1.99 ± 0.12 fold, respectively. HIF‐1α shRNA blocked albumin‐induced increases in collagen‐I (0.54 ± 0.037 vs. 2.13 ± 0.037) and TIMP‐1 (0.76 ± 0.093 vs. 1.99 ± 0.12) protein levels. Furthermore, overexpression of prolyl‐hydroxylase 2 (PHD2) transgene, an enzyme promoting the degradation of HIF‐1α, significantly attenuated albumin‐induced increases in collagen‐ I(0.53 ± 0.21 vs. 1.81 ± 0.30) and TIMP‐1 (0.59 ± 0.19 vs. 1.23 ± 0.16) levels, whereas silencing of PHD2 gene remarkably enhanced albumin‐induced increase in collagen‐I level (2.48 ± 0.77 vs. 1.81 ± 0.30). It is suggested that HIF‐1α mediates albumin‐induced profibrotic effects in renal tubular cells and that manipulating PHD2/HIF‐1α pathway may be used as a therapeutic strategy in chronic kidney diseases.

Grant Funding Source: support by NIH grant HL089563 and HL106042