bluuebunny/crossref_metadata_2025 huggingface dataset:
Postmyocardial infarction remodeling in male and female middle‐aged rats causes a comparable decline in left ventricular systolic properties (680.1)
Authors: Dedkov Eduard , Santos Adora Tricia , Bogatyryov Yevgen , Chen Yue‐Feng , Pingitore Alessandro
Published: June 2021

Our previous study on post‐MI male and female middle‐aged rats has revealed the regional sex‐specific differences in the adaptive changes of the left ventricular (LV) cardiac myocytes and coronary vessels. However, the impact of such structural alterations on LV systolic properties remained unclear. Therefore, our current study is aimed to determine whether post‐MI cardiac remodeling in middle‐aged rats associates with sex‐related differences in LV systolic performance, function or contractility. A large MI was induced in 12‐month‐old male (M‐MI) and female (F‐MI) Sprague‐Dawley rats by ligation of the left coronary artery. Two months after the surgery, the various LV parameters were compared between the sexes using echocardiography, hemodynamics and morphometry. We found that although both sexes had a similar scale of global post‐MI LV remodeling, the F‐MI rats showed a significantly lesser degree of cardiac myocyte hypertrophy in the epimyocardium compared to males (353.3±21.4 vs. 479.0±20.6 μm², P蠄0.01). Nevertheless, rats in M‐MI and F‐MI groups demonstrated comparable values of stroke volume (0.23±0.03 vs. 0.17±0.02 mL), ejection fraction (28.1±3.9 vs. 38.68±4.74 %) and peak dP/dt (3068.3±240.6 vs. 3307.0±214.1 mmHg/sec). Thus, our data reveal that male and female middle‐aged rats have a similar degree of deterioration in LV systolic properties associated with cardiac remodeling after a large MI.
Modest weight gain and weight loss alter expression of sex hormone binding globin in healthy men: implications for endothelial function (680.15)
Authors: Singh Prachi , Covassin Naima , Singh Ravinder , Cundrle Ivan , Sert‐Kuniyoshi Fatima , Romero‐Corral Abel , Davison Diane , Lopez‐Jimenez Francisco , Jensen Michal , Somers Virend
Published: June 2021

Background: Decreased testosterone (TTST) and sex hormone binding globin (SHBG) contribute to development of cardiometabolic disorders in obese men. We aimed to determine the effect of weight gain and weight loss on TTST and SHBG in healthy men and to examine their relationship with endothelial function.

Method: 25 normal weight healthy men underwent an overfeeding protocol to gain 5% body weight over 8 weeks. Following weight gain, they underwent 8 weeks of weight loss. TTST, SHBG and endothelial function (brachial artery flow‐mediated dilation, FMD) were measured at baseline (T1), after weight gain (T2) and after weight loss (T3).

Results: Volunteers gained 4 ± 1.3 kg and subsequently lost 3.2 ± 1.5 kg of body weight. TTST levels did not change (T1: 18.85 ± 6.2 nmol/L, T2: 19.3 ± 6.9 nmol/L, T3: 20.3 ± 7.6 nmol/L). However, SHBG decreased during weight gain (p=0.04) and increased during weight loss (p=0.0005) (T1: 22.8 ± 10.5 nmol/L, T2: 20.8 ± 11.1 nmol/L, T3: 25.58 ± 11.5 nmol/L). Furthermore, SHBG reduction during weight gain tended to correlate with decreases in FMD (p=0.06; R2=0.15). During weight loss, increases in SHBG correlate negatively with changes in FMD (p=0.008; R2=0.32).

Conclusion: In normal weight healthy men, SHBG decreases with modest weight gain and increases with weight loss. TTST does not change. Changes in SHBG partly predict improvements in endothelial function with weight loss.

Grant Funding Source: Supported by AHA 11SDG7260046, R21 DK81014, AHA 13POST16420009
Influence of sexual dimorphism on endothelial morphology, metabolism and mechanics (680.18)
Authors: Huxley Virginia , Stockard Kevin , Bingaman Susan
Published: June 2021

Microvessels are dynamic complexes of vascular structures, formed elements of blood carried by plasma, parenchymal cells, and the interstitial matrix through which they course. Only recently how these elements interrelate to maintain homeostasis differently, often subtly, in females (F) and males (M) is being studied and the implications recognized. We tested the hypothesis that the phenotype of the endothelial cells (EC) lining the vasculature, known to differ by organ and vessel type, would not differ with sex. EC isolated from the aorta and microvasculature of skeletal muscle (SKM) and mesentery (MES) of F and M adult rats were studied with respect to morphology, growth, metabolism and mechanics. We rejected our hypothesis as profound sex‐differences existed for each EC source. For example, F aortic EC were smaller (13 vs 16 μm) and their numbers in culture were greater than M; in SKM and MES F>M (16 vs 15 and 18 vs 15 μm, respectively). Sex and tissue differences were noted for VE Cadherin, eNOS, Insulin receptor β, androgen receptor, and estrogen receptor α and β expression. With respect to fiber orientation and frequency as assessed by atomic force microscopy, overall actin fiber orientation converged in one direction more uniformly in F than M and differed by tissue source. While aortic EC lactate production was sex‐independent, F<M for microvessel EC. Understanding sexual dimorphism in EC will assist in delineating the sources of sex‐differences that influence both the incidence and severity of disease

Grant Funding Source: Supported by NIH DK 095501 and MU Div of Pulm & Critical Care Medicine
Cardiac proteome analysis of sex and estrogen receptor β effects in pressure overload (680.4)
Authors: Kararigas Georgios , Fliegner Daniela , Forler Stefanie , Klein Oliver , Schubert Carola , Klose Joachim , Regitz‐Zagrosek Vera
Published: June 2021

The cardiac response to pressure overload (PO) differs between the sexes and estrogen receptor (ER) β is considered cardioprotective. However, the underlying mechanisms are poorly understood. We aimed at the analysis of the effects of sex and ERβ in PO taking a proteomic approach. Two‐month‐old C57BL6 male (M) and female (F) wild‐type (WT) and ERβ knockout (BERKO) mice were subjected to transverse aortic constriction (TAC) or sham surgery (n = 4/group). The proteome of left ventricular samples was separated by high‐resolution 2‐dimensional polyacrylamide gel electrophoresis. At nine weeks post operation, TAC led to a greater increase in heart‐weight‐to‐tibia‐length ratio in WT M (128%; P < 0.05) than in WT F (54%; P < 0.05) mice, while this difference in BERKO mice between M (53%; P < 0.05) and F (55%; P < 0.05) was abolished. Our comparative proteomic analysis revealed that in WT M and F mice 82 and 31 protein spots, respectively, differed between sham and TAC (P 蠄 0.05). In BERKO M and F mice we found 114 and 87 altered protein spots, respectively (P 蠄 0.05). Among others, trifunctional enzyme subunit family members were repressed in M‐WT‐TAC mice, while cytoskeletal proteins were induced in F‐WT‐TAC mice. On the other hand, heat shock proteins were induced in both M and F‐BERKO‐TAC mice. In conclusion, our study demonstrates that both sex and ERβ influence the proteomic response of the heart to PO.

Grant Funding Source: German Research Foundation (DFG, FG 105, GK 754)
Influence of the baroreflex on the evolution of ventriculo arterial coupling (681.3)
Authors: Bras‐Rosario Luis , Nunes Cecilia , Moura Alexandra , Rocha Isabel , Pinto Fausto , Sequeira Adelia
Published: June 2021

The Baroreflex is a negative feedback mechanism that controls arterial blood pressure, as sensed by the baroreceptors, increasing or decreasing sympathetic and parasympathetic activity to restore arterial blood pressure. It is an important component of arterial blood pressure and circulatory regulation and therefore a fundamental mechanism in the pathogenesis of Hypertension and Congestive Heart Failure, that is further stressed by the multiple therapeutic approaches designed to influence it. As the Baroreflex influences the heart rate, cardiac contractility and vascular resistance, we hypothesised that it must influence the mechanical interaction between the left ventricle and the arterial tree as well as cardiac energy consumption and efficiency.

The ventriculoarterial coupling was evaluated on a beat‐per‐beat basis, upon the application of a left‐carotid sinus baroreflex stimulus in rabbits. The left ventricle end‐systolic elastance and arterial elastance were calculated and the coupling ratio was then related to the indexes of cardiac energetics. Upon the application of the baroreflex, the coupling ratio showed an approximately linear increase, attributed to the rise in ventricular elastance. Stroke work and cardiac efficiency both increased, indicating that not only was the stroke work greater, but it was obtained at a lower oxygen cost. The coupling ratio increased indicating that it was moving towards an optimal stroke work.

In conclusion the baroreflex is a control mechanism of the cardiovascular system that exerts a feedback modulation on the arterial pressure through a balanced increase in cardiac contractility and arterial input impedance which results in an improvement in ventriculo arterial coupling, mechanical and energetic efficiency.

This approach can now be applied to test acute interventions on the circulatory system, including the short term reflexes as mechano reflexes and chemoreflexes, diseases such as myocardial infarction, drug and device therapy.

Grant Funding Source: Fundaçao Ciencia e Tecnologia
Blockade of CB1 receptors reveals that elevated medullary endocannabinoids contribute to age‐related impairment of baroreflex sensitivity in Sprague‐Dawley rats (681.4)
Authors: Schaich Chris , Thomas Brian , Grabenauer Megan , Howlett Allyn , Diz Debra
Published: June 2021

In the solitary tract nucleus (NTS), angiotensin (Ang) II attenuates whereas Ang‐(1‐7) enhances baroreflex sensitivity (BRS) for control of heart rate. Hypertensive (mRen2)27 rats have low medullary Ang‐(1‐7) relative to Ang II associated with impaired BRS that is restored by CB1 receptor blockade in the NTS, consistent with elevated 2‐arachidonylglycerol (2‐AG) in dorsal medulla relative to SD rats. Sprague‐Dawley (SD) rats develop elevated systolic blood pressure as they age, which is associated with impaired BRS resulting from reduced NTS Ang‐(1‐7). We now report that older SD rats exhibit higher 2‐AG at ~70 versus ~15 wks of age (3.9 ± 0.6 vs 1.8 ± 0.3 ng/mg tissue; p < 0.02, n = 4 ‐ 6 each group). Anandamide also tended to be higher in older rats; however, levels were 1000‐fold lower than 2‐AG. Consistent with the elevated endocannabinoids (EC) in dorsal medulla, CB1R antagonist SR141716 (36 pmol/120 nl) microinjection into NTS of older SD rats increased BRS (0.53 ± 0.08 baseline vs 1.06 ± 0.6 msec/mm Hg 60 min after SR141716; p < 0.05, n = 3). In conclusion, elevated ECs within the NTS appear to contribute to the BRS impairment observed in older SD rats.

Grant Funding Source: Supported by NIH: P01‐HL51952, R01‐DA03690, and RTI International
Exacerbated α‐adrenoceptor‐mediated vasoconstriction in obese rats during anesthesia (681.8)
Authors: Lamberts Regis , de Leeuw Anne , Bussey Carol
Published: June 2021

Obese patients undergoing surgery have a higher risk of cardiovascular complications due to an unidentified instability in blood pressure (BP) regulation. The sympathetic nervous system is a crucial BP regulator, acting through α‐ and β‐adrenoreceptors (ARs), and is influenced by anesthesia. Our study aimed to determine how obesity alters cardiovascular AR responsiveness in vivo, and how this is affected by anesthesia.

Sixteen week old Male Zucker Obese rats (n=7) and lean littermates (n=7) underwent dual implantation surgery. A radiotelemeter in the abdominal aorta provided mean arterial pressure (MAP) and heart rate (HR), and a vascular access port in the femoral vein provided non‐invasive intravenous access. Animals were injected with incrementing doses of dobutamine (2‐120 µg/kg) or phenylephrine (1‐100µg/kg) to stimulate β‐ or α‐ARs respectively, under conscious and anesthetized (2% isoflurane) conditions.

Obese animals displayed a reduced HR increase to β‐AR stimulation under conscious conditions (103±12 vs. 61±9 bpm; p<0.001 at 15µg/kg), which was lost during anesthesia (51±3 vs. 66±5 bpm; NS at 15µg/kg). α‐AR stimulation elicited greater increases in MAP in conscious obese rats (53±5 vs. 70±3 mmHg; p<0.01 at 8µg/kg), an effect that was exacerbated by anesthesia (41±5 vs. 69±4 mmHg; p<0.001 at 8µg/kg). Interstingly, obesity interacted with anesthesia, resulting in a significantly prolonged α‐AR‐mediated elevation in MAP compared to lean animals.

Thus, both α‐AR and β‐AR dysfunction are observed in obesity, and are differently affected by anesthesia. The inability of obese patients to appropriately alleviate excess BP during anesthesia may cause undue pressures on the heart and contribute to their perioperative complications.
Estrogen inhibit salt‐overload induced hypernatremia in ovariectomized female rats (683.5)
Authors: Araujo Iracema , Mecawi André , Vilhena‐Franco Tatiane , Dos‐Santos Raoni , Elias Lucila , Antunes‐Rodrigues José , Reis Luís
Published: June 2021

Since estrogen is controversially implicated on sodium balance, our aim in the present study was to evaluate the estrogen modulations on female rats under basal and salt‐overload conditions. Female Wistar rats were bilaterally ovariectomized (OVX) and randomly divided in two groups to receive estradiol benzoate (EB‐OVX, 10 µg/0.1 mL/animal, s.c.) or vehicle (OVX, 0.1 mL/animal, s.c.). The animals were placed in metabolic cages for adaptation; 7 days after the estradiol or vehicle treatement beggining, two experimental protocols were performed in OVX and EB‐OVX rats: i) basal water or water plus saline (0.075, 0.15 and 0.3 M NaCl) offering and, ii) salt‐overload (0.3 M NaCl offered as only fluids) during 3 or 15 days. OVX and EB‐OVX rats exhibited a decreased 0.3 M saline preference compared to hypotonic and isotonic solutions. Also, salt overloaded rats showed a progressive increase of hypertonic intake, as only fluid offered, with no changes induced by estrogen. However, estrogen induced a inhibition of hypernatremia on EB‐OVX rats induced by high salt ingestion when compared to OVX. Additionally, AVP and OT increasing in response to salt loading was not modulated by estrogen, meanwhile estrogen inhibited and attenuated the decrease on ANP and ANG II plasma concentrations, respectively. Taken together, our present findings suggest that estrogen participates on the control of natremia in salt‐overloaded rats.

Grant Funding Source: Supported by FAPERJ and FAPESP
Antidepressant‐like effects after chronic treatment with zinc chloride (684.14)
Authors: Seara Fernando , Laureano‐Melo Roberto , Novais Renata , Araujo Iracema , Almeida Claudio , Conceicao Rodrigo , Reis Luis , Silva Alba , Cortes Wellington
Published: June 2021

This study aimed to elucidate, for the first time, the effects of chronical oral treatment with zinc chloride on the depressant‐like behavior of Wistar rats and correlate them with the neuroendocrine profile promoted by our protocol. Two groups of male Wistar rats (200‐250 g) were treated with zinc chloride (15 mg/kg n=16) or isotonic saline (n=17) during 30 days. The rats were kept in a controlled room temperature with light/dark cycle and food ad libitum. After the treatment, both groups were submitted to a behavioral assessment in an open field (OF), elevated plus maze (EPM) and forced swim (FS) test for five minutes. Moreover, basal plasma corticosterone, triiodothyronine (T3), thyroxine (T4) were measured. Also, iodothyronine deiodinase type 2 (Dio2) activity in brown adipose tissue (BAT) and hippocampus were assessed. In view of our results, chronic treatment with orally zinc chloride does not alter the spontaneously locomotor activity as assessed by OF. However, zinc‐treated group showed anxiolytic effects as shown by less time of grooming (P<0,05), even though the episodes of grooming did not differ between groups. Corroborating the aforementioned anxiolytic effects on OF, zinc treatment reduced the time spent in closed arms (P<0,01) and the number of fecal pellets (P<0,05) on EPM. Yet, zinc‐treated group showed fewer immobilization time compared to control group on FS (P<0,05). Regarding to neuroendocrine profile, zinc‐treated group showed higher plasmatic T3 (P<0,01), however there were no differences on serum corticosterone and T4. Furthermore, there were no differences on Dio2 activity on BAT and hippocampus. We can conclude that chronically treatment with orally zinc chloride provides antidepressant‐like effects and discrete anxiolytic‐like effects during adulthood, presumably by raising plasma T3 level with no involvement of Dio2, taking into account that rodents with signs of depression‐like behavior often present hypothyroidism.

Grant Funding Source: FAPERJ/CNPq
Effectiveness of humor on short‐term memory function and cortisol levels in age matched elderly and diabetic subjects vs. control group (684.4)
Authors: Bains Gurinder , Berk Lee , Daher Noha , Lohman Everett , Petrofsky Jerrold , Schwab Ernie , Deshpande Pooja
Published: June 2021

With ageing, the damaging effects of stress can impair the ability to learn and sustain memory. The purpose was to examine the effect of watching a humor video on short term memory in 3 age matched elderly groups: elderly (69.9 ± 3.7 years), diabetic (67.1 ± 3.8 years), and control (68.7 ± 5.5 years) (no video). Humor and the associated mirthful laughter can reduce stress by decreasing the stress hormone cortisol. Excess cortisol can damage hippocampal neurons leading to impairment of learning and memory. The standardized neuropsychological memory assessment tool, Rey Auditory Verbal Learning Test (RAVLT) was used to assess for 1) learning ability, 2) recall ability, and 3) visual recognition ability. Salivary cortisol measurements, at 3 predetermined time points, were obtained. RAVLT was given to 30 elderly individuals before and after watching a humor video of their choice for 20 minutes vs. no humor video. Results showed that 1) learning ability improved by 38.45% , 33.38%, and 23.96% in the elderly, diabetic, and control groups respectively (p=.025); 2) delayed recall improved by 43.61%, 48.10%, and 20.25% in the elderly, diabetic, and control groups respectively (p=.064); and 3)visual recognition increased by 12.55%, 16.72%, and 8.33% in the elderly, diabetic, and control groups respectively (p=.321). Results, for the changes in salivary cortisol levels, at the predetermined time points, indicated there were 1) borderline significant changes in the elderly group (p=.047, .046, and .062 respectively), 2) significant changes in the diabetic group (p=.047, .025, and .035 respectively), and 3) no changes in the control group (p=.323, .323, and .187 respectively). Due to decreased cortisol levels, elderly and diabetic elderly individuals that watch a humor video that induces mirthful laughter vs. not watching a humor video have greater enhancement in: 1) capability to learn, 2) have greater recall, and 3) improve visual recognition in short term memory function.
Postoperative cognitive dysfunction depends on the type of surgery (684.6)
Authors: Hovens Iris , Schoemaker Regien , van der Zee Eddy , van Leeuwen Barbara
Published: June 2021

The risk of postoperative cognitive dysfunction (POCD) is higher after cardiac surgery compared to non‐cardiac surgery. The objective of this study was to compare POCD after cardiac and non‐cardiac surgery in rats as tool to study the underlying mechanisms.

Male Wistar rats received abdominal surgery with ischemia‐reperfusion (i.r.) of the upper mesenteric artery (A‐S, n=12) or cardiac surgery with i.r. of the left coronary artery (MI‐S, n=12). Controls remained naive (C: n=12), received only anesthesia (A: n=12) or sham thorax surgery (T‐S, n=12). Weight loss accounted for severity of surgery. On postoperative day 10 to 14, cognition was assessed in the novel object and location test and Morris water maze (MWM).

Location recognition was impaired in A‐S and MI‐S. Only A‐S displayed impaired spatial memory in the MWM, whereas only MI‐S displayed impaired object recognition and cognitive flexibility in the MWM. T‐S or A did not cause any cognitive impairment. All surgical procedures induced weight loss. MI‐S lost more weight than A‐S.

Abdominal surgery only impaired spatial cognition, whereas cardiac surgery led to a more generalized cognitive dysfunction, indicating POCD depends on the type of surgery. Analysis of (neuro)inflammatory markers may reveal the basis of these findings and thus provide valuable insight in the mechanisms underlying POCD.
Convergent protein signaling in cerebral cavernous malformations (685.5)
Authors: Tsai Eric , Stockton Rebecca
Published: June 2021

Cerebral Cavernous Malformations (CCMs) are vascular brain lesions affecting 0.5% of humans. Late stage lesions are clusters of grossly dilated capillaries lacking smooth muscle cell or pericyte support, and can cause hemorrhagic stroke. No treatment exists other than surgical removal of symptomatic lesions. CCMs occur sporadically through spontaneous mutations, or by familial autosomal dominant transmission of mutations in three genes : KRIT1, CCM2 or CCM3 (PDCD10). Our lab’s previous work showed that KRIT1 and CCM2 normally regulate endothelial permeability through regulation of RhoA and ROCK1/2. We now used proteomics and CHO cell co‐immunoprecipitations to identify a signalosome consisting of a unique brain microvascular endothelial cell‐specific splice variant of Rap1‐interacting junctional protein MAGI, “MAGI1C‐beta2”, that binds to KRIT1 and CCM2 through a PDZ domain to mediate translocation of two CCM proteins to endothelial junctions, and is required to maintain barrier function. We further identified a MAGI‐1 interacting protein , AMOT (angiomotin) as a convergence point for all three CCM protein signaling pathways, by showing that PDCD10 interacts directly with AMOT at junctional complex , while KRIT1 and CCM2 are localized there through MAGI1C‐beta2. The intact CCM1‐2‐3/MAGIC‐beta2/ AMOT complex suppresses RhoA activation, providing a mechanistic explanation for some aspects of CCM lesion development.

Grant Funding Source: NIH
Angiotensin II stimulates reactive oxygen species production in PVN microglial cells via TLR4 receptor activation (686.1)
Authors: Biancardi Vinicia , Stern Javier
Published: June 2021

Reactive oxygen species (ROS) has been highlighted as a mechanism by which Angiotensin II (AngII) exerts its deleterious effects in cardiovascular diseases. Yet, the precise cellular targets and mechanisms underlying AngII‐ROS production remain unknown. Since toll like receptor 4 (TLR4) in microglia cells can lead to ROS production, we hypothesize here a pathophysiological link between AngII, TLR4 and microglial cells in ROS production within the hypothalamic paraventricular nucleus (PVN). We found co‐immunostaining between microglial cells (IBA1), TLR4 and AT1 receptors within the PVN, providing anatomical evidence for such a crosstalk. Using dihydroethidium (DHE) to evaluate in situ ROS production, we found that AngII (1 μΜ), increased DHE within the PVN of rats (~65%, P<0.001) when compared to DHE in the presence of vehicle. AngII‐ROS production was decreased in the presence of the microglia inhibitor minocycline (100 μΜ; ~31%, P<0.05) suggesting microglia involvement in AngII‐ROS production. To determine the contribution of TLR4 to AT1‐ROS production, we used TLR4 sufficient and deficient mice (C3H/HeJ). We observed that AngII increased PVN DHE in TLR4 sufficient mice (~28%, P<0.05), an effect that was absent in TLR4 deficient mice. Taken together, these studies support a major contribution of microglial TLR4 to AngII‐mediated oxidative stress within the PVN.

Grant Funding Source: Supported by RO1 HL 090948.
Insulin in the arcuate nucleus increases sympathetic nerve activity via extracellular signal‐regulated kinases (686.12)
Authors: Streiff Cole , Cassaglia Priscila , Shi Zhigang , Li Baoxin , Brooks Virginia
Published: June 2021

Intracerebroventricular (ICV) insulin infusion increases SNA, which can be prevented by prior brain inhibition of ERK activation; however, the brain site of ERK activation is unknown. To test the hypothesis that ERK is involved within the site of action of insulin, the arcuate nucleus (ArcN), we first determined if bilateral ArcN nanoinjection of the ERK inhibitor PD98059 (60 nL of 0.5 mM/L) prevents the increases in lumbar SNA (LSNA) induced by ArcN insulin (60 pU in 30 nL) in α‐chloralose‐anesthetized male rats. ArcN insulin increased LSNA from 101±3 to 130±6 % control (P<0.05; n=5). PD98059 alone had no effects (108±9 to 112±8 % control), but subsequent ArcN insulin failed to increase LSNA (105±7 to 102±2 % control; n=4). In contrast, ArcN insulin still increased LSNA (106±4 to 147±24 % control; P<0.05) following ArcN blockade of PI3K (LY294002; 60 nL of 0.5 mM/L; n=5). Next, insulin (100 µU/min; n=3) or aCSF (0.6 µL/min; n=3) was infused ICV for 35 min, followed by dual ArcN immunohistochemistry of activated ERK and the insulin receptor (InsR). While there was no difference in the number of ArcN InsR immunoreactive (‐ir) neurons between insulin‐infused (223±17) and aCSF‐infused (263±21) rats, activated ERK‐ir was found only in the ArcN of insulin infused rats (137±13 vs. 7±2 neurons; P<0.05), with 34±6% of InsR‐ir neurons also expressing activated ERK‐ir. In conclusion, ArcN insulin increases LSNA via ERK signaling, possibly within the InsR‐responding neuron.

Grant Funding Source: Supported by HL088552 and AHA.
Hydrogen peroxide modulates barium‐sensitive K+‐currents of nucleus tractus solitarii neurons (686.14)
Authors: Ostrowski Tim , Hasser Eileen , Heesch Cheryl , Kline David
Published: June 2021

The nTS holds a vital role in cardiorespiratory reflexes as the first central integration site of chemosensitive afferents. Hypoxia‐reoxygenation over‐produces H2O2, a potent neuromodulator and reactive oxygen species. We previously found in rat brainstem slices that second‐order nTS neurons initially reduce excitability when exposed to 500 µM H2O2. This was due to a reversible hyperpolarization in resting membrane potential (RMP; ‐10 mV) and reduction in membrane resistance (Ri; ‐224 MΩ). Since these effects occur at RMP (~ ‐60 mV), we determined the effect of H2O2 on K+ channel conductance using voltage steps and ramps between ‐100 and ‐50 mV in nTS slices. H2O2 increased the slope of holding currents during steps by 1.31 ±0.35 nS (N=6, p蠄0.01). Such currents reversed at ‐75 mV, indicating greater K+ conductance. Augmented conductance (+ 0.49 ±0.18 nS; N=5, p蠄0.05) by H2O2 was also observed during voltage ramps. Conductance changes persisted during blockade of glutamate and GABAA receptors, confirming such effects were not secondary to synaptic activation. H2O2‐induced alterations of RMP, Ri and slope conductance were eliminated by barium (100 µM), a blocker of inward rectifying (IRK) and 2‐pore‐domain (K2P) K+ channels. Altogether, the H2O2 induced increase in barium‐sensitive K+ conductance is likely an immediate response to increased ROS and mediates decreased neuronal activity.

Grant Funding Source: Supported by: RO1 HL098602, AHA 12POST11670002 (TDO).
Overexpression of copper/zinc superoxide dismutase (SOD1) in the median preoptic nucleus attenuates chronic angiotensin II hypertension in the rat (686.16)
Authors: Collister John , Bellrichard Mitch , Nahey David , Tian Jun , Zimmerman Matthew
Published: June 2021

The brain senses circulating levels of AngII via circumventricular organs such as the subfornical organ (SFO), and can adjust sympathetic nervous system output accordingly. Previous lesion studies of either the SFO or the downstream MnPO have shown a diminution of the hypertensive effects of chronic AngII, without providing a clear explanation as to the intracellular signaling pathway(s) involved. Additional studies have reported that overexpressing SOD1, an intracellular superoxide (O2•‐) scavenging antioxidant enzyme, in the SFO attenuates chronic AngII‐induced hypertension. Herein, we tested the hypothesis that overproduction of O2•‐ in the MnPO is an underlying mechanism in the long‐term hypertensive effects of chronic AngII. Adenoviral vectors encoding human SOD1 (AdSOD1) or control vector (AdEmpty) were injected into the MnPO of rats implanted with aortic telemetric transmitters for recording of arterial pressure. After a 3 day control period of saline infusion, rats were intravenously infused with AngII (10 ng/kg/min) for ten days. Rats overexpressing SOD1 (n=4) in the MnPO had a blood pressure increase of only 4+2 mmHg after seven days of AngII infusion while blood pressure rose 20+4 mmHg in AdEmpty‐infected rats (n=6). These results support the hypothesis that production of O2•‐ in the MnPO contributes to the development of chronic AngII‐dependent hypertension.
Overexpression of copper/zinc superoxide dismutase (SOD1) in the median preoptic nucleus improves cardiac function after myocardial infarction in the rat (686.17)
Authors: Collister John , Hartnett Cristina , Mayerhofer Tim , Nahey David , Stauthammer Christopher , Kruger Maxie , O'Sullivan Gerry , Parker Josh , Tian Jun , Zimmerman Matthew
Published: June 2021

Previous reports indicate that overexpression of SOD1, an intracellular superoxide (O2•‐) scavenging enzyme, in the brain subfornical organ improves cardiac function in a mouse model of heart failure (HF). A downstream hypothalamic site, the MnPO, may act as a relay center for O2•‐to act as a mediator in the pathophysiology of HF. To test the hypothesis that elevated O2•‐ in the MnPO contributes to the pathophysiology of HF and decreased cardiac function, we injected adenovirus encoding SOD1 (AdSOD1, n=4) or control empty vector (AdE, n=4) into the MnPO of normal rats. Subsequently, rats were subjected to coronary artery ligation to create a myocardial infarct (MI) of the left ventricle. Cardiac function was monitored at 2 week intervals via echocardiography. Upon completion, rat brains were examined for SOD1 expression in MnPO via immunofluorescence and histopathological analyses of cardiac infarct size were conducted. Baseline (EF) ejection fractions (%) of AdSOD1 and AdE rats were 69±2 and 72±3, respectively. One week after MI, EF was significantly decreased in both groups of rats (AdSOD1: 44±5, AdE: 49±2). In contrast by 5 weeks post MI, EF had improved to 55±3 in AdSOD1 rats yet was only 42±4 in AdE rats. In conclusion, despite decreases in EF early after MI, overexpression of SOD1 in the MnPO was related to an improvement in left ventricular function 5 weeks post MI.
Intracerebroventricular injection of Tityustoxin increases the cardiovascular parameters and renal sympathetic nerve activity (686.18)
Authors: Silva Fernanda , Marins Fernanda , Fontes Marco , de Menezes Rodrigo , Guidine Patrícia , Chianca Deoclécio
Published: June 2021

The scorpion envenoming is an important public health problem in tropical and subtropical countries. Despite, clinical studies address the high sensitivity of the central nervous system to Titystoxin (TsTX) action, mainly in infants, few studies focus on the central action of the scorpion toxins. Because of this we aimed to assess if the cardiovascular parameters and renal sympathetic nerve activity (RSNA) could be altered by a central injection of a very low dose of TsTX (0.116µg), which is more than 20,000 times less concentrated than those used in peripheral experiments. Urethane anesthetized wistar male rats (n=5) were submitted to: 1) tracheostomy to airway maintenance, 2) arterial and vein femoral cannulation to measure the cardiovascular parameters and drugs infusions, 3) location of the left lateral ventricle to PBS and TsTX injection (1μl) and 4) isolation of renal nerve to measure the RSNA. Mean arterial pressure (MAP), Heart Rate (HR) and RSNA records were done before (20 min for baseline and PBS periods) and after TsTX injection (60 min). TsTX period was divided in: beginning (B), midlle (M) and final (F). Methods were approved by Ethical Committee (CEUA/UFOP:2011/46;2013/49). Results were expressed as mean ± SEM. Naturally, PBS did not changes the parameters. But, TsTX increased the MAP(Δ):(B)= 15±7, (M)=21±9, (F)= 21±12mmHg; p =0,0005; HR(Δ): (B)=45±19, (M)=74±22, (F)= 82± 25 bpm; p=0,0039 and (ΔRSNA,% of baseline: (B)=101±18; (M)=187±26, (F)= 254±38; p< 0,0001. These results indicate a high sensitivity of blood pressure and HR control nuclei and the huge RSNA responsiveness to the central action of a very low dose of TsTX.

Grant Funding Source: Supported by UFOP, CAPES, FAPEMIG and CNPq
Angiotensin II receptor type‐1a knockdown in subfornical organ prevents sustained increase in mean arterial pressure associated with chronic intermittent hypoxia (686.20)
Authors: Saxena Ashwini , Little Joel , Nedungadi Thekkethil , Cunningham J
Published: June 2021

Sleep apnea (SA) is associated with a sustained increase in mean arterial pressure (MAP) even during waking hours. Chronic intermittent hypoxia (CIH) models the hypoxemia associated with SA and produces elevated MAP during CIH and normoxia. Angiotensin II (Ang II) is implicated in the CIH associated increase in MAP. Subfornical organ (SFO), a forebrain circumventricular organ, lacks blood brain barrier and is a major site for the central effects of circulating Ang II. We investigated the effects of Ang II type 1a receptor knockdown (AT1aRKD) in the SFO on CIH hypertension in adult male rats. Adeno‐associated viral vectors carrying GFP and either AT1aR shRNA or scrambled shRNA (SCM) were injected in SFO. Using laser‐capture microdissection and qRT‐PCR of amino‐allyl RNA, AT1aRKD rats showed decreased SFO AT1aRmRNA in comparison with SCM rats (p<0.05). During light phase, the AT1aRKD rats exposed to CIH(3 min 10% O2 and 3 min room air cycles for 8 h during light phase for 7 d) exhibited significant increases in MAP vs. AT1aRKD‐Normoxia group (p<0.05). During the normoxic dark phase, there was no difference in MAP between CIH and normoxic AT1aRKD rats (p=0.69). SCM‐CIH group showed significant increase in MAP from SCM‐Normoxia group during light phase CIH (p<0.001) and the normoxic dark phase (p<0.001). Our data indicate that AT1aRs in SFO may play a role in the sustained increases in MAP during normoxia associated with CIH.

Grant Funding Source: Supported by: P01HL088052‐05
Hering‐Breuer evoked regulation of respiratory rhythm variability in rats (686.25)
Authors: Dhingra Rishi , Galan Roberto , Dick Thomas
Published: June 2021

Hering‐Breuer‐related afferent activity affects respiratory patterning in disparate ways: constant mechanical ventilation entrains the respiratory rhythm; yet removal of vagal feedback reduces respiratory rhythm variability. We hypothesize that these effects are mechanistically linked and test this hypothesis by closing the Hering Breuer Reflex feedback loop via rhythmic vagal nerve stimulation in situ before and after suppressing activity in the nucleus tractus solitarii (nTS) or Kölliker‐Fuse nuclei (KFn) by microinjection of muscimol, a GABAAR agonist. We measured feedback‐evoked entrainment of respiration and the variability of the rhythm in the presence or absence of periodic vagal feedback. Rhythmic vagal feedback evoked periods of entrainment interposed by phase slips. Analysis of respiratory rhythm variability revealed that vagal feedback amplified intrinsic respiratory rhythm variability via the transitions from a phase slip to stable entrainment. Suppressing nTS activity eliminated both entrainment and variability amplification. Suppressing KFn activity increased entrainment strength, reduced phase slip frequency and blunted variability amplification. We conclude that 1) Hering‐Breuer feedback inputs are sufficient to amplify respiratory variability via a noisy synchronization mechanism and 2) both entrainment and variability depend on KFn and nTS activity.

Grant Funding Source: Supported by NS069220 and T32 HL007913
Nucleus tractus solitarii reactive oxygen species contribute to acute intermittent hypoxia‐induced long‐term facilitation of phrenic and splanchnic sympathetic nerve activity (686.26)
Authors: Ostrowski Daniela , Ruyle Brian , Allison Kleiber , Kline David , Heesch Cheryl , Hasser Eileen
Published: June 2021

Cardiorespiratory neural networks undergo alterations in function (plasticity) that are critical to homeostasis but can be deleterious, as in obstructive sleep apnea (OSA). AIH in rats (10X: 45 sec of 10% O2 every 5 min) mimics cardiorespiratory changes as in OSA; prolonged increases in ventilatory/phrenic and sympathetic activity (AIH‐LTF) and augmented hypoxia (Hx) responses post‐AIH. The nTS integrates and modulates primary cardiorespiratory input and undergoes plasticity in response to changes in afferent input, including to Hx. nTS ROS are increased by intermittent Hx and important for plasticity. We hypothesized that nTS ROS contribute to AIH‐LTF and augmented Hx responses post‐AIH. Bilateral microinjection of the antioxidant catalase (CAT, 500 U/ml; 60 nl) in the nTS prior to each Hx bout during AIH attenuated AIH‐LTF for both integrated phrenic amplitude and splanchnic sympathetic nerve activity (%Δ: PhrA, Con=152±58, n=9; CAT=27±19, n=6; SSNA, Con=51±6, n=9; CAT=34±7, n=8). CAT also diminished augmented Hx responses post‐AIH (%Δ vs. Hx1st: PhrA, Con=76±37; CAT=14±22; SSNA, Con=90±11; CAT=50±13). In separate animals, chronically decreasing nTS ROS by injecting a viral vector overexpressing human catalase (AdCAT) also attenuated AIH‐LTF (%Δ: PhrA, Con=77±23, n=8; AdCAT=‐21±15, n=4; SSNA, Con=27±8; AdCAT=1±17). Data suggest nTS ROS contribute to phrenic and sympathetic AIH‐LTF. HL98602

Grant Funding Source: Supported by HL98602
Angiotensin converting enzyme 1 knockdown in the median preoptic nucleus attenuates sustained diurnal hypertension following chronic intermittent hypoxia (686.29)
Authors: Faulk Katelynn , Nedungadi T. Prashant , Cunningham J. Thomas
Published: June 2021

Chronic Intermittent Hypoxia (CIH) is a model for the arterial hypoxemia seen in sleep apnea and is associated with a sustained increase in blood pressure throughout the diurnal cycle. Studies indicate that the MnPO contributes to this sustained component of CIH hypertension that persists during normoxia. MnPO neurons from rats show increased expression of the transcription factor FosB following CIH. Dominant‐negative inhibition of a FosB splice variant in MnPO attenuates the sustained hypertension in CIH. We identified the pro‐hypertensive ACE1 as a possible FosB target gene that may contribute to the sustained hypertension seen in CIH. We tested this hypothesis using a viral vector to knockdown ACE1 in the MnPO. Isoflurane anesthetized adult male rats were microinjected in the MnPO with 500nl of an adeno‐associated virus containing GFP and either shRNA against ACE1 (shACE1) or a scrambled shRNA (shSCM). Changes in Mean arterial blood pressure (MAP) were recorded using radio telemetry. Rats were then exposed to CIH for 7 days through 3 minute periods of hypoxia (10% oxygen) and 3 minute periods of normoxia (21% oxygen) for 8 hours per day (0800‐1600 h). Normoxic controls were exposed to room air. Laser capture microdissection followed by qRT‐PCR showed that shACE1 significantly decreased ACE1 message in MnPO. During CIH exposure, MAP significantly increased in both shACE1 and shSCM treated rats. During the normoxic dark phase, knockdown of ACE1 in the MnPO statistically decreased the sustained MAP component of CIH as compared to shSCM controls (P<0.001). These results show that ACE1 in the MnPO contributes to the sustained hypertension seen in our CIH model.

Grant Funding Source: P01 HL88052
Cortical and subcortical contributions to muscle sympathetic nerve activity in awake humans: a functional connectivity fMRI analysis (686.30)
Authors: Macefield Vaughan , James Cheree , Henderson Luke
Published: June 2021

Purpose: Using direct microelectrode recordings of muscle sympathetic nerve activity concurrently with functional magnetic resonance imaging (fMRI) of the human brain, we have been able to identify the cortical and brainstem regions responsible for the generation of spontaneous muscle sympathetic nerve activity (MSNA). In the present study we aimed to determine the functional connectivity between these regions. Methods: A tungsten microelectrode was inserted percutaneously into a muscle fascicle of the common peroneal nerve, at the level of the fibular head, to record MSNA in 14 subjects. Gradient echo, echo planar fMRI was performed using a 3T scanner. Two hundred scans were collected continuously in a 4s‐ON, 4s‐OFF protocol. Total sympathetic burst amplitudes were measured from the RMS‐processed mean voltage amplitude during the 2‐4 s interval of the 4s‐OFF period, so as to account for the temporal location of the hypothalamus in the caudorostral scanning direction. A fixed‐effects group analysis (minimum cluster size=10 voxels, p<0.005) was performed to identify a volume of interest for use as a ‘seeding area’. A connectivity analysis was then performed (fixed‐effects, minimum cluster size=10 voxels, p<0.005) with the ventromedial hypothalamus being used as a ‘seeding area’. Results: The ventromedial hypothalamus showed positive relationships with the left dorsomedial hypothalamus and anterior insula, precuneus and right dorsolateral prefrontal cortex and rostroventral lateral medulla bilaterally. Conclusions: Spontaneous fluctuations in sympathetic nerve activity to muscle covaries with activity in multiple brain regions, supporting the idea that the hypothalamus contributes to the ongoing control of resting blood pressure and may be driving other brain regions involved in the control of MSNA.

Grant Funding Source: NHMRC
123I‐MIBG scintigraphy suggests functional sympathetic reinnervation in human renal allografts (687.1)
Authors: Dobrowolski Linn , Verberne Hein , ten Berge Ineke , Bemelman Frederike , Krediet C.T.
Published: June 2021

After kidney transplantation, sympathetic renal nerves may reinnervate the allograft, but its functional significance is unknown.123I‐metaiodobenzylguanidine (123I‐MIBG) scintigraphy determines organ specific sympathetic innervation (uptake) and activity (washout rates, WORs). Therefore we applied 123I‐MIBG scintigraphy to assess the functionality of sympathetic nerves in human renal allografts.

We studied 5 patients with a median allograft survival of 20 years (range 11‐36), creatinine clearance 89 ml/min (56‐118). Their immunosuppressive drug regimen consisted of azathioprine and prednisolone. None of them was treated with either alpha‐ or beta‐blocking agents.

After intravenous administration of 185 MBq 123I‐MIBG, scintigrams were made at 15 min and 4 hr postinjection (p.i.) and a CT scan was made for anatomical localization of the tracer. Uptake was calculated as % of injected dose 123I‐MIBG. WORs in the myocardium, native left kidney and renal allograft were deducted from 15 min and 4 hr scintigrams. For WORs the relative uptake was used in relation to non‐specific uptake (i.e. mediastinum). Median % injected dose uptake in the myocardium, native left kidney and renal allograft was 3.7, 5.5, 3.8% at 15min p.i. and 3.3, 4.8 and 1.6% at 4hr p.i. respectively. WORs were 4.8, 6.7 and 26%.

These data suggest some functional sympathetic reinnervation in long surviving human renal allografts. The use of renal 123I‐MIBG scintigraphy should be validated and functional significance of this sympathetic reinnervation in renal allografts will be further studied.

Grant Funding Source: Dutch Kidney Foundation (IP 11‐40)
Capsaicin‐mediated selective afferent renal nerve denervation: effects on intrarenal responses to bradykinin and adenosine in conscious Sprague‐Dawley rats (687.2)
Authors: Wainford Richard
Published: June 2021

Aim: It has been reported that capsaicin evokes selective denervation of the renal afferent nerves in rats as confirmed by IHC. We assessed the efficacy of capsaicin‐mediated afferent denervation in preventing the physiological responses to activation of the renal afferent nerves.

Methods: Conscious Sprague‐Dawley rats implanted with an ICV cannula, having undergone sham (S) or renal afferent nerve denervation (ADNX) (capsaicin 33mM), received IV and IR infusions of bradykinin (BK) (5‐40 μg/kg/min) and adenosine (A) (2‐12 μg/min). All animals then received ICV guanabenz (50ug) (N=4/gp). HR, MAP and sodium excretion were continuously monitored.

Results: IR BK dose‐dependently increased MAP and HR in sham animals and had no effect on MAP or HR in ADNX rats (BK 40 μg/kg/min; peak ΔHR [bpm] S +61±8 vs ADNX ‐5±3, P<0.05; peak ΔMAP [mmHg] S +19±3 vs ADNX +0.6±2, P<0.0.5). IV BK did not alter MAP or HR at any dose tested in S or ADNX rats. IR, but not IV, adenosine evoked a dose‐dependent increase in natriuresis in sham animals, a response that was abolished following ADNX (A 12 μg/min; peak ΔUNaV [ueq/min] S +18.7±3 vs ADNX +2±0.4, P<0.05). In both sham and ADNX rats, ICV guanabenz evoked profound bradycardia, hypotension and natriuresis (guanabenz 50 μg; peak ΔUNaV [μeq/min] S +13.4±1 vs ADNX +12.8±1).

Conclusion: These data provide compelling evidence that the recently described technique of capsaicin mediated afferent renal denervation prevents the physiological responses to intrarenal administration of established activators of the renal afferent nerves. Further, central α2‐adrenoceptor activation evoked a profound natriuretic response mediated by suppression of efferent nerve activity in sham and ADNX rats. This indicates the presence of viable and functional renal efferent nerves following ADNX. Collectively these data demonstrate it possible to selectively denervate renal afferent nerves without affecting the function of the renal efferent nerves.

Grant Funding Source: Support by R01HL107330 & K02HL112718A1
Enzamin improves adipose tissue inflammation with impaired adipocytokine expression and insulin resistance in obese mice (688.1)
Authors: Matsuo Osamu , Tamura Yukinori , Yano Masato , Kawao Naoyuki , Ueshima Shigeru , Kaji Hiroshi
Published: June 2021

Aim: Effects of Enzamin, which is a product from Bacillus subtilis AK and Lactobacillus, on obesity‐related metabolic disorders in obese db/db mice were examined to explore a novel agent for the prevention of insulin resistance.

Methods and Results: Db/db mice were treated with water containing Enzamin (0.1% and 1.0%) for 8 weeks from 6 weeks of age. Enzamin treatment at 1.0% significantly decreased the fasting plasma glucose, serum total cholesterol and triglyceride levels in db/db mice. Furthermore, insulin resistance was improved by the treatment of db/db mice with Enzamin. Enzamin suppressed macrophage accumulation and inflammation in the adipose tissue and increased serum adiponectin in db/db mice. Enzamin also significantly suppressed the expression of NADPH oxidase subunits, suggesting an anti‐oxidative effect of Enzamin in the adipose tissue. Enzamin increased the mRNA expression of GLUT4 and carnitine palmitoyltransferase 1a in muscle of db/db mice. Further, in vitro experiments demonstrated that the lipopolysaccharide‐induced inflammatory reaction was significantly suppressed by Enzamin in macrophages.

Conclusion: Our data indicates that Enzamin can improve insulin resistance by ameliorating impaired adipocytokine expression, presumably through its anti‐inflammatory action, and that Enzamin possesses a potential for preventing metabolic syndrome.

Grant Funding Source: None