bluuebunny/crossref_metadata_2025 huggingface dataset:
Astaxanthin and Olive Oil Pretreatment Improves Recovery of Motor and Cognitive Skills in a Closed Head Injury TBI Model in Male Sabra Mice
Authors: Fleischmann Chen , Shohami Esther , Heled Yuval , Horowitz Michal
Published: June 2021

Impact related traumatic brain injury (TBI) commonly influences high‐risk populations such as contact sports athletes and combat soldiers. Recovery results in mild to severe loss of motor and cognitive function. Prophylactic protection to enhance resilience and improve the rate and extent of recovery by nutrient supplementation is currently limited. Astaxanthin is a natural xantophyll carotenoid supplement which readily crosses the blood brain barrier (BBB) and was previously shown to improve recovery in a brain ischemia‐reperfusion model when administered post injury.

The study objective was to examine the effects of Astaxanthin pre‐supplementation on the motor and cognitive aspects of recovery from a closed head injury (CHI) model in mice.

Methods

male sabra mice were treated with Astaxanthin 100 mg/Kg per day in olive oil by gavage (XO), or olive oil (O) or in pellet form as 1% Astaxanthin in animal food by free eating (X) for 2 weeks, exposed to a CHI model, and followed over a one month recovery period. Motor skills were assessed using the neurological severity score (NSS) at 1, 24, 48, and 72 hours and weekly post injury. Cognitive skills were assessed using the Open filed, and Y‐Maze tests on days 2 and 29 post injury, and the novel object recognition (ORT) test on days 3 and 30 post injury.

Ethics: all animal experiments were approved by the Hebrew University authority for biological and biomedical models ethical review board (registration numbers: MD‐13‐13734‐4 & MD‐16‐14842‐4).

Results

NSS scores revealed a significant improvement in motor skills recovery (ΔNSS=1.25±0.16 vs. 0.5±0.27 in XO vs. O, respectively, p=0.001), which began on week 2 and lasted to 4 w. Additional cognitive improvement was demonstrated in the Y‐maze on Day 29: 44.57±3.22% vs. 36.46±1.95% of exploration time spent in the novel arm for XO vs. O, respectively, p=0.03). The results of the open field and ORT tests did not significantly differ between groups.

When Astaxanthin supplementation was administered in pellet form (X), a considerably smaller influence was observed in the NSS compared to XO, while cognition (open field, Y‐Maze, ORT) remained unaffected. Post injury X supplementation with or without pre supplementation did not improve results.

Conclusion

Results suggest an advantage to XO over X and O in motor and cognitive skills recovery. The results of the effect of XO on NSS and on cognitive function, versus the lack of similar motor and cognitive effects with X, suggest a contribution of the combined XO administration to motor and cognitive parameters and warrants further work to elucidate its mechanism as well as the effects of post injury XO supplementation.

Support or Funding Information

This work was funded by the IDF medical corps research authority

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Conditioned Place Preference of Mice Selectively Bred for High Voluntary Wheel Running
Authors: Schmill Margaret P. , Cadney Marcell D. , Hiramatsu Layla , Albuquerque Ralph , Buenaventura Darrius G. , Louis Monica P. , Castro Alberto A. , Thompson Zoe , Kay Jarren C. , Ramirez Jocelyn L. , Garland Theodore
Published: June 2021

Running acts as a natural reward and shares features with other rewarding behaviors, such as eating or taking drugs of abuse. Exercise is even proposed to have addictive properties, as humans and rodents have shown signs of “withdrawal,” including anxiety and depression, after being denied exercise. Conditioned place preference (CPP) is a neuro‐behavioral test of reward and reinforcement, widely used in studies of addictive processes in rodents. In typical protocols, individuals receive a reward (e.g., cocaine injection) paired with a specific environment (usually a specific floor texture) several times and are then tested for preference of the conditioned environment as compared with a different environment in which they had not received a reward (e.g., saline injection). We studied CPP in a unique exercise model of 4 replicate lines of mice selectively bred for high voluntary wheel running (High Runner or HR lines) and 4 non‐selected control (C) lines. HR mice run ~3‐times as much as C mice on a daily basis, partly because of evolutionary changes in their reward and motivational systems. We hypothesized that HR mice would differ from C in the extent to which they show a CPP following conditioning with rewarding drugs and/or wheel running. In experiment 1, HR and C mice were tested for CPP with cocaine as the reward. Both HR and C mice were significantly conditioned by cocaine, with no statistical difference between groups in the degree of conditioning. In experiment 2, mice were tested for CPP with wheel access as the reward. Specifically, mice were granted or not granted wheel access for 10 days, and each day removed from wheels or standard cages during peak wheel running and placed in CPP chambers for 30 minutes. Preliminary results show no significant conditioning by either HR or C mice. In a recent experiment 3, mice were tested for CPP with Ritalin as the reward, following the same protocol as experiment 1. Functioning as a dopamine transporter blocker, the drug Ritalin has been shown to decrease wheel running of HR mice while increasing running by C mice. Thus, we hypothesize a significant difference in the degree of conditioning between HR and C mice with Ritalin.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Spinal Conversion of Testosterone to Estradiol for the Expression of Phrenic Long‐term Facilitation in Adult Male Rats
Authors: Dougherty Brendan J. , Tyurina Elena , McIntosh Danielle
Published: June 2021

Estrogen modulates the expression of neuroplasticity, including phrenic long‐term facilitation (pLTF), a persistent increase in phrenic nerve activity observed after acute exposure to intermittent hypoxia (AIH; three 5 min episodes of 10.5% O2, delivered at 5‐minute intervals). Though robustly expressed in adult males, adult female rats express pLTF only in the presence of adequate circulating estradiol (E2); removal of the ovaries, the primary source of circulating E2, abolishes pLTF. Acute, spinal application of membrane‐impermeable E2 (E2‐BSA) restores plasticity in ovariectomized female rats through a fast‐acting cellular mechanism involving membrane‐associated estrogen receptors, suggesting spinal E2 signaling may be important for pLTF expression in females. Previous studies indicate that E2 may play an important role in the expression of AIH‐induced pLTF in adult male rats as well. Specifically, gonadectomy blunts pLTF expression by reducing circulating testosterone, and systemic testosterone replacement restores pLTF. However, this testosterone‐induced restoration of pLTF is only effective in the presence of aromatase, an enzyme that converts testosterone to E2. Here we tested the hypothesis that the relevant conversion of testosterone to E2 necessary for expression of pLTF in male rats occurs in the spinal cord near phrenic motor neurons. We recorded phrenic nerve activity and pLTF expression in anesthetized, paralyzed and ventilated male Sprague‐Dawley rats (3–4 mos) in the presence or absence of intrathecally delivered Letrozole, an aromatase inhibitor, over the cervical spinal cord. We combined these data with immunohistochemical characterization of aromatase expression in the ventral cervical spinal cord. Collectively, these data provide important information regarding the necessity for spinal E2 signaling in the expression of AIH‐induced pLTF in male rats, and underscore the utility of this model to dissect the role of E2 signaling in expression of spinal neuroplasticity.

Support or Funding Information

Funding: This work was supported by the University of Minnesota Division of Physical Therapy with a generous contribution from the University of Minnesota Department of Rehabilitation Medicine.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Lack of Uncoupling Protein 3 Protects from High‐Fat Diet‐Induced Insulin Resistance and Glucose Intolerance in Rats
Authors: Lomax Tyler M. , Wiseman Jessica M. , Edwards Kristin S. , Ashraf Sadia , Harmancey Romain
Published: June 2021

Uncoupling protein 3 (UCP3), a mitochondrial anion carrier regulating fatty acid metabolism, is down‐regulated in type 2 diabetes. Whether UCP3 decrease influences the development of obesity and insulin resistance is currently unclear. We investigated the effect of genetically‐induced partial (UCP3+/−, with a 50% decrease in protein levels) or total (UCP3−/−) deficiency in whole body UCP3 on metabolic fitness in rats. Two lines of UCP3 deficient rats (hereinafter referred to as 1‐bpINS and 22‐bpDEL) were independently generated on a Sprague Dawley background strain using CRISPR‐Cas9 genome editing. Male UCP3 deficient rats and their wild type littermates were maintained on a chow diet or fed a high‐fat diet (HFD) for 14 weeks starting at 8 weeks of age. Metabolic fitness was assessed by analyzing body composition with EchoMRI and by performing insulin and glucose tolerance tests. Although both rat lines had similar lean‐to‐fat ratio and body mass under normal feeding conditions, the 22‐bpDEL line had higher circulating levels of lipids, insulin, and leptin, and was less insulin sensitive and glucose tolerant than the 1‐bpINS line. Partial or total UCP3 deficiency did not cause changes in body weight gain, body composition, or insulin sensitivity when rats were maintained on a chow diet. However, partial and total UCP3 deficiency increased glucose clearance at 15 min following intraperitoneal glucose injection in both rat lines. Compared to chow diet, high‐fat feeding significantly increased weight gain and fat mass while simultaneously impairing insulin sensitivity and glucose tolerance in both rat lines. In the 1‐bpINS line, loss of UCP3 decreased fat mass gain without altering food consumption so that UCP3−/− rats presented higher lean‐to‐fat ratio compared to wild type littermates. Loss of UCP3 improved insulin sensitivity in HFD‐fed 1‐bpINS rats, with a protective effect that was more prominent in UCP3−/− than in the UCP3+/− animals. Likewise, the gradual loss of UCP3 improved glucose tolerance in 1‐bpINS rats and prevented the increase of the glucose area under the curve (AUC) for UCP3−/− rats when compared to chow‐fed values (AUC 20219 vs. 15667 for wild type, P < 0.0001; AUC 18724 vs. 15376 for UCP3+/−, P < 0.01; AUC 17224 vs. 15007 for UCP3−/−, P = 0.4). This improvement of metabolic fitness associated with UCP3 deficiency was absent in rats from the 22‐bpDEL line. In conclusion, loss of UCP3 unexpectedly preserves metabolic fitness in male rats under high‐fat feeding. This protective effect depends on genetic background.

Support or Funding Information

Supported by grants R00 HL112952, P01 HL051971, and P20 GM104357 from the National Institutes of Health

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
A pilot study on the effects of hormonal contraceptives on beta‐arrestin1 levels in peripheral blood mononuclear leukocytes
Authors: Smith Keisha , Rana Tanu , Archibong Anthony E. , Nayyar Tultul
Published: June 2021

OBJECTIVE

Women are twice as likely as likely as men to develop depression during reproductive years. Use of hormonal contraceptives, during reproductive years, may be causal with development of depression in a subgroup of women because observational studies indicate an association between use of progestin (Depo‐Provera) and development of depressive symptoms. Previously we have reported reduced levels of beta arrestin 1(β‐AR‐1) during premenstrual depressive disorder, may be a potential biomarker of depression. In this study we compared the β‐AR‐1 protein levels and the Hamilton Depression Rating Scores (HDRS) as well, in women on non‐hormonal contraceptives (control), combine‐only contraceptives (COC), and progestin‐only contraceptives (POC).

METHODS

Study participants (n=29) were non‐pregnant women between 18–42 years of age, not taking any antidepressants/therapy and at the luteal phase of menstruation. The participants were evaluated with Neuropsychiatric Interview (DSMIV‐TR). The severity of depression were determined by the HDRS. The protein levels of beta‐arrestin1 in the in peripheral blood mononuclear leukocytes (PBMC) were determined by ELISA.

RESULTS

The magnitude of the different parameters for Axis 1 mental disorders were significantly higher and beta arrestin1 protein levels in PBMC were significantly lower in women currently using progestin‐only contraceptives as compared to the control.

CONCLUSION

These findings indicate the possibility of reduced levels of β‐AR‐1 and associated symptoms of depression in a subgroup of women may results from the use of POC.

Support or Funding Information

Clinical Research Education and Career Development in Minority R25RR17577 (NCRR/NIMHD) and U54 MD007593 (NIMHD) and U54 RR026140 (NCRR) at NIH.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sex‐Related Effects of Nesfatin‐1 in the Pituitary
Authors: Schnell Abigayle Lyn , Pate Alicia , Samson Willis K. , Yosten Gina LC.
Published: June 2021

Neuroendocrine interaction between the hypothalamus, pituitary, and adrenal glands, known as the HPA axis, is responsible for regulation of the adaptive stress response. Nesfatin‐1, a potent anorexigenic peptide expressed in the hypothalamus, has been shown to play a role in the stress response by modulating HPA axis activity in rats. However, elucidation of nesfatin‐1's cognate receptor is necessary to assess the physiological relevance of these findings. Previous data on the nesfatin‐1 signaling pathway indicate involvement of a G‐protein‐coupled receptor. Furthermore, because the stress‐response is known to be sexually dimorphic, we hypothesized that the action and expression of nesfatin‐1 would be influenced by sex hormones. In cultured male rat pituitary cells, treatment with nesfatin‐1 elicits a robust cFos response, but no significant response was observed in female rat pituitary cells. In addition, expression of nesfatin‐1 in the female rat hypothalamus differed across stages of the estrus cycle. To determine the physiological relevance of nesfatin‐1's effects, we also began screening cell lines responsive to nesfatin‐1 for orphan GPCR expression to search for a candidate receptor. These studies suggest that both expression and function of nesfatin‐1 are regulated by sex hormones. Identification of the nesfatin‐1 receptor would potentially yield a novel therapeutic target for stress‐related disorders.

Support or Funding Information

NIH HL121456

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
PARTIAL PROGESTERONE DEPRIVATION ALTERS THE TRANSCRIPTION OF ESTROGEN RECEPTORS AND THEIR DOWNSTREAM GENES IN RAT PLACENTAS
Authors: Albader Maie , El‐Farra Aseel , Narayana Kilarkaje
Published: June 2021

Objective

To investigate the role of progesterone in placental growth and effects on the expression of estrogen receptors‐alpha and ‐beta and their downstream genes.

Materials and Methods

Pregnant SD rats were segregated into A) control (peanut oil, twice daily injections), B) ovariectomized on 15 day gestation (dg), with progesterone restoration, and C) progesterone reduction groups. To restore estrogen levels, estradiol was administered subcutaneously using mini‐osmotic pump (40 ng/h) and then injected to maintain normal increase in plasma levels of the hormone. In group B, progesterone level was restored by administering the hormone daily and, in group C, progesterone reduction (partial deprivation) to one third of the normally observed level of the hormone on 22 dg was maintained. Placentas were harvested on 19 dg and 21 dg and dissected into basal and labyrinth zones. Gene expression of estrogen receptors‐alpha and ‐beta, p53, Bax and Bcl‐2 was analyzed by real time‐polymerase chain reaction. Data were analyzed by one way ANOVA and Least square difference test with the level of significance set p<0.05.

Results

Partial progesterone deprivation decreased placental and basal zone weights on 19 dg (p<0.05), which was not restored by progesterone restoration to normal levels. Progesterone restoration did not recover decreased fetal body weights in overiectomized rats although placental efficiency was not affected on 21 dg. Partial progesterone deprivation increased the transcription of both estrogen receptors in the basal zone on 19 dg (p<0.05), which recovered to normal levels after progesterone restoration. Similarly, p53, Bax and Bcl‐2 gene expressions were also increased in the basal zones in partial progesterone deprived rats, which were restored to normal levels on 19 dg and 21 dg, after progesterone restoration. A similar pattern was seen in the labyrinth zone on 16 dg and 19 dg.

Conclusion

Partial progesterone deprivation inhibits placental and fetal growth most probably by enhancing estrogen receptor‐mediated up‐regulation of apoptosis in placentas. Progesterone is essential for normal growth of placentas and fetuses in rats.

Support or Funding Information

Kuwait University Research Grant # MY02/08

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Cardiovascular Susceptibility in Offspring After Maternal Engineered Nanomaterial Exposure
Authors: Stapleton Phoebe
Published: June 2021

Cardiovascular disease (CVD) is the leading cause of death worldwide and associated with many genetic and lifestyle risk factors. The maternal health and fetal milieu during gestation has been explored as a contributing factor to progeny health. Engineered nanomaterials (ENM) are manufactured within the nanoscale (<100 nm in one dimension) to take advantage of specific physiochemical properties. Exposure to these materials has become more prolific given their pervasiveness in domestic applications, yet the outcomes during pregnancy and for developing young are currently unknown. Gestational ENM exposure led to impairments in uterine microvascular reactivity in early studies, indicative of the development of a hostile gestational environment. The Barker Hypothesis theorizes that development is such an environment will influence cardiovascular health later in life.

Studies were initiated to assess the cardiovascular health during growth from a late‐stage fetus to young adult after maternal ENM inhalation. Pregnant, healthy Sprague‐Dawley rats were exposed to nano‐sized titanium dioxide aerosols (10.4±0.1 mg/m3 for 4h, aerodynamic diameter of 136.5±1.4 nm, calculated daily pulmonary deposition of 39.7±1 μg, initiated on gestational day [GD] 5.78±0.13 for 7.78±0.26 days of the remaining pregnancy). As indices of litter health, the number of fetal pups on GD 20 did not differ between control and exposed (12.2±0.9 vs. 10.8±1.5); however, the size of the placenta (0.76g±0.02 vs. 0.68±0.02) and number of surviving pups (11±0.7 vs. 6±1) were significantly different. As microvascular health can characterize early cardiovascular health, reactivity was assessed via a pressurized isolated microvessel preparation where the arterioles of the tail (fetal [GD 20], neonate [6±0.48d] or heart (weanling [25.7±0.9d], juvenile [7.64±0.4w], adult [10.36±0.34w]) progeny were dissected, excised, and evaluated in response to chemical stimuli to calculate endothelium‐dependent (acetylcholine [10−9–10−4 M]), ‐independent (spermine‐NONOate [10−9–10−4 M]), and vascular smooth muscle (phenylephrine [10−9–10−4 M]) function. Significant temporal impairments in endothelium‐dependent reactivity were identified in exposed fetal (−37.2%±7.3), juvenile (−29.1%±11.3), and adult (−59.3%±17.1 vs. control, respectively) progeny. Further, studies of mitochondrial stress reveal significant reductions in calculated ATP production of isolated cardiomyocytes during development where fetal (23%±3), neonate (83%±3), weanling and juvenile (63%±9), and young adult (75%±2) measurements are below control. Overall, exposure to ENM during gestation may increase CVD susceptibility, thereby compromising health of future generations.

Support or Funding Information

NIH‐R00‐ES024783 (PAS); P30‐ES005022

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Early life stress (ELS) protects against LNAME hypertension‐induced renal tubular damage
Authors: Obi Ijeoma , Pollock David , George James , Pollock Jennifer
Published: June 2021

In humans, early life stress (ELS) is a newly recognized cardiovascular disease risk factor and associated with increases in inflammation and risk of hypertension. Utilizing a rat model of ELS, maternal separation (MatSep), we recently reported that MatSep induced immune activation in the kidney compared to normally‐reared control animals. Chronic nitric oxide synthase blockade with LNAME in the drinking water is a model of hypertension with increased immune cells and inflammation. Therefore, we hypothesized that exposure to MatSep during early life and LNAME during adulthood would induce increased levels of renal injury markers and immune cells when compared to normally‐reared rats with LNAME during adulthood. MatSep involves separating rat pups from the dam for 3hrs/day from postnatal day 2 (PD2) to PD14. Normally‐reared littermate rats were used as controls. Twelve weeks old adult (n=6–8rats/group) control and MatSep rats were given LNAME (100mg/kg/rat) in drinking water for 7 days. LNAME was adjusted daily based on the amount of water intake. We compared urinary renal damage markers and renal immune cell populations in control and MatSep rats after LNAME treatment. On day 7 after LNAME, urine was collected for assessment of glomerular (albumin and nephrin) and tubular (KIM1 and NGAL) injury markers by enzyme‐linked immunosorbent assay (ELISA). Our results showed that urinary KIM1 excretion was significantly lower in MatSep rats compared to control rats (control LNAME vs. MatSep LNAME: 6.78mg/day ± 0.32 vs. 5.53mg/day ± 0.36; p = 0.029). No statistical differences were observed in urinary NGAL, albumin and nephrin excretion. At day 7 after LNAME, blood and kidneys were used for determination of immune cell populations by flow cytometry. The proportion of renal total T cells, T helper cells, macrophages, neutrophils, natural killer, and dendritic cells were similar in control and MatSep rats. However, there was a trend towards an increase in the proportion of cytotoxic T cells in MatSep compared to control animals (%CD45+ cells; control LAME vs. MatSep LNAME: 14.04 ± 0.97 vs. 17.37 ± 1.35; p = 0.087). No differences were observed in the proportion of circulating immune T helper cells, cytotoxic T cells, macrophages, neutrophils, natural killer, and dendritic cells in control and MatSep rats. Our findings suggest that MatSep during early life may protect from tubular injury in response to inhibition of nitric oxide synthase. Future studies are warranted to determine whether the observed renal tubular protection is linked to LNAME induced blood pressure elevation, loss of tubular nitric oxide production, and T cell activation.

Support or Funding Information

Funded by Cardiovascular Pathophysiology NIH/NHLBI T32HL007918‐19 to IEO, R01DK059600 to JFG, and P01HL69999 to JSP.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
How do the Carotid Chemoreceptors Modulate Ventilatory Control and Cardiovascular Regulation at Rest and During Exercise in COPD?
Authors: Phillips Devin , Collins Sophie , Steinback Craig , Bryan Tracey , Wong Eric , McMurtry Michael Sean , Bhutani Mohit , Stickland Michael
Published: June 2021

RATIONALE

We have recently demonstrated elevated activity and sensitivity of the carotid chemoreceptor (CC) in COPD, which may alter ventilatory and cardiovascular regulation at rest and during exercise. Accordingly, we sought to examine whether CC inhibition modifies ventilation and cardiovascular regulation at rest and during exercise in COPD.

METHODS

In a randomized double blind crossover study, thirteen COPD patients (FEV1 predicted ± SD: 82 ± 19%) and thirteen healthy controls completed resting cardiovascular function measurements while receiving either intravenous (I.V.) saline or I.V. dopamine (2 mg/kg/min) while inspiring either room air or 100% O2 (order randomized). Participants then completed two time to symptom limitation constant load exercise tests at 75% peak power output, on separate days, while receiving either I.V. saline or dopamine (order randomized). At rest, arterial stiffness was determined by pulse‐wave velocity (PWV) and muscle sympathetic nerve activity (MSNA) was measured by microneurography. Ventilatory responses were evaluated using expired gas data and cardiac output (impedance cardiography) was collected to calculate vascular conductance (cardiac output/mean arterial pressure (MAP)). Exertional dyspnea was evaluated using a modified Borg scale and inspiratory capacity maneuvers were performed to determine operating lung volumes.

RESULTS

At rest, CC inhibition with dopamine decreased central and peripheral PWV, ventilation and MAP (p<0.05) while increasing vascular conductance in COPD. No change in CV function was observed with dopamine in controls. CC inhibition with hyperoxia decreased peripheral PWV and MSNA (p<0.05) in COPD, while no change was observed in controls. At a standardized exercise time (isotime) of 4 minutes and at symptom limitation, minute ventilation was not different between saline and dopamine conditions in COPD or controls. Operating lung volumes and exertional dyspnea were not different between conditions within either group. Vascular conductance was increased (p<0.05) during exercise with dopamine in COPD, secondary to reduced MAP, while no change was observed in controls. There was no change in time‐to‐exhaustion in either group with dopamine.

CONCLUSION

Results from the current study suggest that the CC plays a role in cardiovascular regulation at rest and during exercise in COPD; however, exercise ventilation, dyspnea and exercise tolerance were unaffected by CC inhibition in COPD patients. Interventions aimed at chronically reducing CC activity may be beneficial to reduce cardiovascular risk in COPD.

Support or Funding Information

Lung Association of Alberta/NWTCanadian Institute of Health Research

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
High Intensity Muscle Metaboreflex Activation Blunts Cardiopulmonary Baroreflex Control of Sympathetic Vasomotor Outflow
Authors: Katayama Keisho , Kaur Jasdeep , Young Benjamin E. , Barbosa Thales C. , Ogoh Shigehiko , Fadel Paul J.
Published: June 2021

Muscle sympathetic nerve activity (MSNA) is reduced during low intensity dynamic leg exercise. This reduction in MSNA has been attributed to loading of the cardiopulmonary baroreflex with increased venous return and it has been suggested that such inhibition is overridden with higher intensity exercise due to muscle metaboreflex activation. However, limited data are available regarding the interaction between the cardiopulmonary baroreflex and the muscle metaboreflex. Herein, we tested the hypothesis that cardiopulmonary baroreflex control of MSNA is attenuated when the muscle metaboreflex is strongly activated. In eight healthy young men, MSNA (right peroneal nerve), mean arterial blood pressure (MAP, Finometer), heart rate (ECG), and thoracic impedance were recorded. Graded isolation of the muscle metaboreflex was achieved by post‐exercise ischemia (PEI) following low‐ (PEI‐L), moderate‐ (PEI‐M) and high‐ (PEI‐H) intensity isometric handgrip performed at 20%, 30% and 40% maximum voluntary contraction, respectively. Lower‐body positive pressure (LBPP, +10 mmHg), to load the cardiopulmonary baroreflex, was applied at rest and during PEI. Handgrip exercise elicited intensity‐dependent increases in MSNA and MAP that were maintained during PEI indicating a graded muscle metaboreflex activation. LBPP at rest significantly decreased MSNA burst frequency and total activity (total activity: −39.5 ± 5.7%, mean ± SE, P < 0.05), while MAP was unchanged. When LBPP was applied during PEI, MSNA burst frequency and total activity decreased significantly at PEI‐L (total activity: −41.8 ± 10.6%, P < 0.05) and PEI‐M (total activity: −34.7 ± 8.6%, P < 0.05), but not at PEI‐H (total activity: −11.8 ± 8.6%, n.s., one‐way repeated measures ANOVA: F = 5.07, P < 0.05). Thoracic admittance, which was calculated from thoracic impedance as an index of central blood volume, was not changed during handgrip or PEI alone, whereas LBPP evoked similar increases in thoracic admittance during all conditions (rest: +5.4±0.8, PEI‐L: +5.8±0.5, +PEI‐M: +5.4±0.5, PEI‐H: +5.8±0.5 S·10−4, one‐way repeated measures ANOVA: F = 0.38, n.s.). These preliminary findings suggest that high intensity muscle metaboreflex activation attenuates cardiopulmonary baroreflex control of sympathetic vasomotor outflow.

Support or Funding Information

NIH R01 HL127071 JSPS KAKENHI Grant Number JP16KK0201

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Intermittent Hypoxia (IH) modulates the effects of Corticotropin‐Releasing Hormone (CRH) on NTS neuronal synaptic transmission
Authors: Jia Shuping , Mifflin Steve
Published: June 2021

We examined if exposure to IH, a model of the arterial hypoxemia that occurs during sleep apnea, modulates the effects of activation of CRH receptors (CHRRs) on NTS neuronal synaptic transmission. Whole‐cell recordings from NTS second‐order arterial chemoreceptor neurons, identified by DiA labeling of carotid bodies, were obtained in a caudal NTS slices (250μM thick). Slices were incubated with 100nM of the CRHR1 selective agonist stressin I or 100nM of the CRHR2 selective agonist urocortin II in aCSF for 20 minutes and slices studies 0.5–2.0 hrs later. Spontaneous miniature excitatory postsynaptic currents (mEPSCs) and inhibitory postsynaptic currents (mIPSCs) were recorded in separate slices under voltage clamp 0.5–2 hours after the 20min agonist incubation from both normoxic controls and slices obtained from rats exposed to IH for 7 days. The CRHR1 selective agonist and antagonist had no any effect on mEPSC amplitude or frequency. The CRHR2 selective agonist urocortin II significantly increased mEPSC amplitude (21.60 ± 1.03pA, n=13 vs 26.74 ± 1.13pA, n=11, p<0.01) in normoxic rats but did not alter mEPSC frequency. Exposure to IH increased mEPSC amplitude and in IH exposed rats urocortin II prevented the IH‐induced increase in mEPSC amplitude (27.42 ± 1.32pA, n=15 vs 22.35 ± 0.82pA, n=14, p<0.01). On the other hand, the CRHR1 agonist stressin I significantly enhanced mIPSC amplitude in slices from control, normoxic rats (32.57 ± 2.31pA, n=10 vs 38.14 ± 1.4pA, n=12, p<0.05), but neither IH nor stressin I altered mIPSC amplitudes and frequency in slices from IH exposed rats. The CRHR2 agonist did not alter mIPSC frequency or amplitude. In separate experiments, 10min prior to incubation of the slice with the CRHR selective agonist, the slice was pre‐treated with either CRHR1 antagonist NBI35965 (1μM) or CRHR2 antagonist K41498 (100nM). The CRHR2 selective antagonist K41498 attenuated the urocortin II effect on mEPSCs and the CRHR1 antagonist NBI35965 attenuated the stressin 1 effect on mIPSCs. Our findings provide evidence that CRH can modulate NTS neuronal glutamatergic transmission and GABAergic transmission through different CRHR subtypes. After IH, CRHR2 receptor activation reverses IH‐inudced increases in mEPSC amplitude, whereas after IH CRHR1 receptor activation no longer increases mIPSC amplitude. These changes appear to be primarily mediated by alterations in the post‐synaptic neuron.

Support or Funding Information

NIH HL088052

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Corticotropin‐Releasing Hormone Receptor 2 in the Nucleus of the Solitary Tract Contributes to the Intermittent Hypoxia Induced Hypertension
Authors: Wang Lei , Nguyen Dianna , Cross Stephanie , Mifflin Steve
Published: June 2021

Our previous study in rats suggested that Corticotropin‐Releasing Hormone (CRH) Receptor 2 (CRHR2) is the predominant CRH receptor in the nucleus of the solitary tract (NTS), a key nucleus that regulates autonomic and cardiovascular functions; exposure to intermittent hypoxia (IH), a model of the arterial hypoxemias that occur during sleep apnea, significantly decreased CRHR2 mRNA levels in the NTS. To study the CRHR2 signaling pathway in the NTS, we performed calcium imaging on NTS slice preparations using Fura‐2‐acetoxymethyl ester. CRH induced a transient increase of intracellular calcium level in NTS neurons that was abolished by the voltage‐dependent calcium channel blocker nifedipine. Calcium influx was attenuated by the CRHR2 antagonist K41498 but not by NBI‐35965, an antagonist for CRH receptor 1 (CRHR1). Calcium influx can be induced by the CRHR2 agonist Urocortin II but not by the CRHR1 agonist Stressin I. More importantly, consistent with the down‐regulation of CRHR2 mRNA after IH exposure, IH exposure also attenuated the CRH‐induced calcium influx in the NTS. Further in vivo pharmacological studies revealed that intra‐4th ventricle infusion of the CRHR2 agonist Urocortin II significantly increased basal blood pressure and exacerbated the IH‐induced hypertension in rats; intra‐4th ventricle infusion of the CRHR2 antagonist K41498 did not affect the basal blood pressure but significantly delayed the onset of IH‐induced hypertension. Considering that the NTS is the major CRHR2‐expressing nucleus in the brain stem that regulates sympathetic activity and blood pressure, these results indicate that activation of CRHR2 in the NTS contributes to the hypertension during IH. To study the source of CRH in the NTS that regulates blood pressure, we expressed Channelrhodopsin 2 (ChR2) specifically into the CRH‐producing neurons in the paraventricular nucleus of the hypothalamus (PVN) by injecting Cre‐inducible viral constructs expressing ChR2 into the PVN of CRH‐Cre mice. We observed significant pressor responses after optogenetic stimulation of CRH somas in the PVN (12.3 ± 1.13 mmHg) or CRH fibers in the NTS that originated from the PVN (3.54 ± 0.69 mmHg), suggesting that activation of CRH projections from the PVN to the NTS increases blood pressure. Collectively, these results suggest that CRH derived from the PVN activates CRHR2 in the NTS, which may contribute to the IH‐induced hypertension; down‐regulation of CRHR2 and CRHR2‐mediated calcium influx in the NTS may serve as compensatory responses to protect against the IH‐induced hypertension.

Support or Funding Information

This study was supported by National Institute of Health HL088052

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Resting regional brain activity and functional connectivity varies with resting blood pressure but not muscle sympathetic nerve activity in normotensive humans
Authors: Macefield Vaughan Gary , Kobuch Sophie , Henderson Luke Anthony
Published: June 2021

Introduction

Mean arterial pressure (MAP) is tightly controlled by the brain, with the rostroventrolateral medulla (RVLM) ‐ the final output nucleus for muscle sympathetic nerve activity (MSNA) ‐ playing a particularly important role. The aim of this study was to investigate the relationships between regional cerebral blood flow (rCBF) ‐ a proxy marker of neural activity ‐ and MAP and MSNA in young, healthy normotensive subjects.

Methods

Pseudocontinuous arterial spin labeling (pCASL) and functional magnetic resonance imaging (fMRI) of the brain were performed immediately following a recording of MSNA and BP in 31 normotensive subjects (13 females, 18 males; mean±SE age: 23.3±3.8 y). Subjects were divided into groups with lower (78.8±1.1 mmHg, n=15) and higher (95.9±1.6 mmHg, n=16) MAP, as well as lower (7.5±0.8 bursts/min, n=16) and higher (22.3±1.9 bursts/min, n=15) MSNA.

Results

Regional cerebral blood flow correlated positively with resting MAP in the RVLM and dorsolateral pons, as well as in the insular, prefrontal and cingulate cortices. Furthermore, functional connectivity analysis revealed that the insular and prefrontal cortices displayed greater resting connectivity within the RVLM in the group with lower MAP, but not in the group with higher MAP. However, no significant differences in rCBF were found when subjects were divided on the basis of MSNA.

Conclusions

These results suggest that small differences in resting MAP are associated with significant differences in resting activity and functional connectivity within brain regions known to contribute to cardiovascular control. It remains to be seen how these relationships are affected in hypertensive individuals.

Support or Funding Information

National Health & Medical Research Council of Australia (GTN1100040)

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Estrogen Receptor Beta and G‐Protein Coupled Estrogen Receptor are Located and Activated on Microglia by Estrogen
Authors: Dvorak Katherine , Boyer Michael , Barnes Maria J. , Clayton Sarah C.
Published: June 2021

Upon menopause, women have an increased risk of cardiovascular disease, in part due to the decrease in estrogen production that occurs. While estrogen's cardioprotective effects have been known for many years, the exact mechanism of this protection is still under investigation. Estrogen receptors have been detected in locales in the central nervous system that are critical in the regulation of arterial pressure and sympathetic nervous activity, particularly the rostral ventrolateral medulla (RVLM) and paraventricular nucleus (PVN) of the hypothalamus. Animal models of menopause implicate over activity of the sympathetic nervous system contributes to hypertension. Microglia are believed to be the resident immune cells of the brain. In previous studies, activated glia have been shown to contribute to increased neuronal tone and excitability in the PVN and RVLM and increased sympathetic activity, potentially through the release of pro‐inflammatory cytokines. The role of microglia in hypertension is not clear. The overall objective of these studies is to investigate if estrogen can regulate the activity of microglia. We sought to evaluate how estrogen regulates its cognate receptors using an immortalized microglia 10‐day old female mouse cell line (EOC2). Utilizing immunohistochemical and western blot techniques, our data demonstrate that the microglia cell line expressed estrogen receptor beta (ERβ) and G‐Protein coupled Estrogen Receptor (GPER). Exposing the cells to 10nM of estrogen for 15 minutes demonstrated that estrogen activates the microglia and initiates ERβ translocation from the membrane to the cytosol. We found a dose (1, 10 and 100 nM) and time (5, 15, 30 and 60 minute) dependent change in the protein level of GPER and ERβ. These results demonstrate that estrogen exposure can activate microglial cells and increase expression of estrogen receptors. Future studies will examine if the activation of microglia by estrogen alters the release of cytokines and thus may modulate neuronal function. These findings will contribute to the pivotal role estrogen plays in central blood pressure regulation and will undoubtedly shed light on possible mechanisms of menopause‐induced hypertension.

Support or Funding Information

S Clayton DMU IOERM Barnes DMU IOER

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Effect of Chronic Vagal Nerve Stimulation on Glucose Tolerance in Conscious Rats
Authors: Stauss Harald M. , Stangl Hubert
Published: June 2021

Previously, we demonstrated that cervical vagal nerve stimulation (VNS) inhibits insulin secretion and markedly increases resting blood glucose levels in anesthetized rats. Based on these findings, we hypothesized that chronic cervical VNS induces impaired glucose tolerance in conscious rats.

All animal experiments were approved by the Institutional Animal Care and Use Committee of The University of Iowa. Rats were chronically instrumented with telemetric blood pressure sensors inserted into the aorta through the femoral artery and right‐sided cervical vagal nerve stimulators. Three and six days following surgery, repeated glucose tolerance tests (1.5 g dextrose/kg BW, i.p.) were performed after overnight fasting with the vagal nerve stimulators on or off (sham stimulation) in randomized order. VNS (3V, 5Hz, 1ms pulse duration, 1h on 1h off) or sham stimulation was started on the day before the glucose tolerance test. The stimulators were switched to a continuous stimulation mode (instead of 1 h on, 1 h off) for the entire duration of the glucose tolerance tests (2–3 hours) and switched off thereafter. Effectiveness of VNS was confirmed in all animals by the heart rate response to VNS (assessed through the telemetric blood pressure sensors).

The study is still ongoing at the time of this writing. Preliminary results from three animals that completed the study so far indicate that baseline blood glucose levels were elevated in animals that received overnight VNS (168±16 mg/dL, n=3) compared to sham stimulated animals (123±15 mg/dL, n=3, P=0.11). The maximal increase in blood glucose levels during the oral glucose tolerance tests (time point 30 min) was greater in rats with VNS (+412±23 mg/dL, n=3) compared to sham stimulated animals (+233±41 mg/dL, n=3, P=0.11). Furthermore, two‐way Analysis of Variance revealed that glucose levels were significantly elevated throughout the 120 min of the glucose tolerance tests in rats with VNS compared to sham‐stimulated animals (P<0.01).

These preliminary results suggest that cervical VNS impairs glucose tolerance in conscious rats. It remains to be determined if human patients treated with VNS are at greater risk to develop type 2 diabetes.

Support or Funding Information

Supported by a pilot grant from the University of Iowa Hospitals and Clinics Center for Hypertension Research and the German Research Foundation.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Thoracic TRPV1 Receptor Spinal Afferent Ablation Prevents the Development and Progression of Hypertension in SHR but Not in Ang II‐infused Rats
Authors: Shanks Julia A. , de Morais Sharon Del Bem Velloso , Wang Hanjun , Zucker Irving H.
Published: June 2021

Sympatho‐excitation is well described in the pathogenesis of hypertension in both clinical and animal models. Increased sympathetic drive to the heart and alerted cardiac spinal afferent signaling have previously been implicated in contributing to the development and progression of hypertension via the cardiac sympathetic afferent reflex (CSAR). However, the role cardiac spinal afferents play in modulating this response is unknown. To address this, we utilized two rat models of hypertension that have previously been described to have a neurogenic component to their phenotype, the spontaneously hypertension rat (SHR) and angiotensin II (Ang II; 240 ng/kg/min) infusion model. To selectively and chronically ablate the CSAR, the afferent specific neurotoxin, a potent TRPV1 receptor agonist, Resiniferatoxin (RTX) was given epidurally at the level of the T1–T4 dorsal root ganglia (DRG; 6 μg/ml, 10 μl/per ganglion). Blood pressure (BP) was monitored using radiotelemetry in the conscious state before and for 1–2 months post RTX. Echocardiograms were performed on all animals, under 2% isoflurane anesthesia, pre‐treatment and at the end of the study to monitor any changes spinal nerve ablation had on cardiac function. Selective ablation of TRPV1 expressing neurons in the DRG was confirmed by immunohistochemistry. In young (8 week) SHR, T1–T4 RTX abolished the increase in blood pressure (BP) observed in vehicle control animals (n = 6, both groups). Thoracic TRPV1 ablation with RTX in older (16 week) SHR with established hypertension significantly reduced BP compared to control (n = 7, both groups). No change in BP to thoracic RTX was observed in Wistar Kyoto rats (n = 5, RTX and control), RTX had no effect on heart rate in any group. To confirm the BP lowering action of RTX in the SHR was site specific to the T1–T4 thoracic (cardiac) DRG, RTX was administered into the lumbar region of the spinal cord (L2–L5) in 16‐week‐old SHR; no change in BP was observed (n = 5, RTX and control). Epicardial application of RTX in 16 week‐old SHR also failed to significantly reduce BP compared to control (n = 6, both groups). RTX treatment 1 week before (n = 3) or 1 week after (n = 5) Ang II infusion did not alter Ang II‐induced hypertension compared to controls (n=3; n=8, respectively). These data suggest that thoracic spinal afferents contribute to the hypertensive process in SHR. We speculate that the SHR exhibit higher levels of sympatho‐excitation compared to Ang II‐hypertension, thereby responding more effectively to elimination of a sympatho‐excitatory input. From these data, the origin of the afferents is inconclusive.

Support or Funding Information

Supported by NIH grant HL 126796 and Sorrento Therapeutics, Inc.

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