bluuebunny/crossref_metadata_2025 huggingface dataset:
Exercise preconditioning prevents skeletal muscle wasting in monocrotaline‐induced cardiac cachexia
Authors: Gonçalves Daniel , Henriques-Coelho Tiago , Ferreira Rita , Fonseca Hélder , Neuparth Maria João , Justino Joana , Duarte Daniela , Vieira Sara , Amado Francisco , Duarte José Alberto , Leite-Moreira Adelino
Published: June 2021

Cardiac cachexia is characterized by an imbalance between anabolic and catabolic factors that lead to weight loss. The present study addresses the preventive effect of exercise training on muscle wasting in an animal model of right ventricular failure induced by monocrotaline (MCT) administration. After 4 weeks of training or cage living, male Wistar rats were injected with MCT (60mg/kg) (ExMCT and SedMCT, respectively) or saline (ExC and SedC, respectively), and sacrificed after an additional 4week‐period of movement confined to cage's space. Gastrocnemius and blood samples were collected for biochemical analysis. Sed+MCT showed decreased body weight, cross sectional area and MHC‐I isoform. Total Akt and mTOR protein levels were normal while its phosphorylated forms were increased in exercised groups. Increased Atrogin‐1 protein expression was found only in Sed+MCT, as well as higher serum levels of CRP and IL‐1b. The present study provides evidence that exercise preconditioning prevents cardiac cachexia by averting proteolysis and inflammation.
Role of epinephrine in the control of protein degradation during fasting
Authors: Graça Flávia A , Lira Eduardo C , Gonçalves Dawit A. P. , Silveira Wilian A , Zanon Neusa M , Kettelhut Isis C , Navegantes Luiz C. C.
Published: June 2021

The present work investigated the physiological role of epinephrine in the control of muscle protein degradation during fasting. For this, 3‐week‐old rats, previously submitted to adrenodemedullation (ADMX; 10 d after the surgical removal of adrenal medulla) were fasted for 2 days. ADMX abolished the plasma epinephrine concentration in both fed and fasted animals but did not affect plasma corticosterone levels. In sham rats, fasting increased overall proteolysis, the activity of ubiquitin‐proteasome system (UPS), the mRNA levels of atrogenes (Atrogin‐1 and MuRF1) and autophagy‐related genes (GABARAPl1 and LC3b). ADMX in fasted animals reduced the cAMP content (30%) in extensor digital longus (EDL) muscles and induced an additional increase of overall proteolysis which was associated with a higher activity of lysosomal (50%) and UPS (2x) systems and expression of atrogenes (~3x) and autophagic genes (~5x). pAkt was reduced (40%) by ADMX in muscles from fed rats. The lower phosphorylation levels of Akt were further decreased by ADMX. The data suggest that depletion of plasma epinephrine exacerbates the catabolic effects of fasting on skeletal muscle protein metabolism probably due to a decrease in cAMP/Akt signaling pathway. Supported by FAPESP (10/11015‐0; 08/06694‐6).
Overexpression of HSP10 in transgenic mice protects skeletal muscle against endotoxic shock‐induced loss of force generation
Authors: Kayani Anna Charlotte , Routley Claire , Douramani Maria Touramani , Dillmann Wolfgang , Mestril Ruben , Jackson Malcolm
Published: June 2021

Impairment of skeletal muscle function and wasting are consistent and severe features of sepsis and are associated with poor outcome. The rate of loss of muscle in septic patients with multiple organ failure is between 2 and 4% per day. We have demonstrated that overexpression of the mitochondrial chaperone HSP10 prevents age related loss of maximum force generation and cross sectional area and we hypothesised that HSP10 would be beneficial in preventing the loss of muscle function during sepsis.

WT and HSP10 overexpressor mice were treated with LPS at 2.5mg/Kg and maximum force generation of EDL muscles was measured after 24hrs. Overexpression of HSP10 resulted in significant protection against LPS induced loss of maximum force generation compared with WT mice and additionally protected against the systemic symptoms of endotoxic shock observed in WT mice. HSP10 overexpression significantly reduced serum protein levels and muscle mRNA content of TNF‐α and IL‐6 compared with WT mice. Muscle fibres were isolated from FDB muscles and treated with LPS at 1μg/ml for 5hr. A significant reduction in the TNF‐α release was observed from fibres from HSP10 overexpressor mice compared with WT.

These data suggest that anti‐inflammatory effects of HSP10 protect against the loss of maximum force and the severity of systemic illness during endotoxic shock and therefore provides a potential therapeutic target in sepsis. Funded by MRC.
MRI‐based screening for metabolic insufficiency of leg muscle during aerobic exercise in Cystic Fibrosis
Authors: Jeneson Jeroen A.L. , Werkman Maarten S , Blanken Niels , van Oorschot Joep , van der Ent Kors , Arets H. G. , Hulzebos H. J. , Takken Tim
Published: June 2021

There is evidence for mitochondrial dysfunction in various tissues in Cystic Fibrosis (CF) including muscle. Among others, a slow rate of high‐energy phosphate resynthesis following exercise involving single limb muscle activity was found in human CF using in vivo 31P magnetic resonance spectroscopy (MRS). This raises the question whether this outcome would be ameliorated versus exacerbated if instead an exercise regime is used that puts a significant cardiopulmonary load on the body as in running or bicycling. This is of interest because exercise therapy is commonly prescribed in CF. To investigate this matter, ten pediatric CF patients (age 12–16 years) and healthy peers performed two ramp exercise tests to volitional exhaustion using a bicycle ergometer fit for use inside a MR scanner. Endurance, VO2max and heart rate were determined in the exercise laboratory. Quadriceps muscle energy‐and acid/base balance during exercise and recovery were measured on a separate day using MR imaging‐based 31P MRS. This study brings together for the first time this powerful biomedical imaging platform and whole body exercise testing in the clinical setting of human CF.
Changes in interstitial ATP levels and blood flow during local heating of human skin
Authors: Gifford Jayson R , Bridges Jarom , Heal Cory , Marshall Brady , Goldthorpe Scott , Mack Gary
Published: June 2021

Heating keratinocytes is believed to activate the transient receptor potential vanilloid type III ion channel (TRPV3) resulting in the release of ATP. We examined the hypothesis that local skin heating would activate keratinocyte TRPV3 channels resulting in an increase in interstitial ATP that would contribute to a rise in skin blood flow (SkBF). Two microdialysis probes were inserted into the dermis on the dorsal aspect of the forearm in 15 young, healthy subjects. To manipulate the level of activation of TRPV3 channels the probed skin was heated to 31, 35, 39, and 43°C for 8 minutes each with an automated peltier device (3 cm x 3 cm). SkBF was monitored as cutaneous vascular conductance (CVC, %peak) and dialysate collected during each heating phase was analyzed for ATP ([ATP]d). At a skin temperature of 31°C [ATP]d averaged 21.70 ± 6.09 nM while CVC averaged 12.57 ±1.59 %peak. Heating the skin to 35°C increased CVC to 17.63 ± 1.27 %peak (p<0.05) while [ATP]d was unchanged. At skin temperatures of 39 and 43°C [ATP]d decreased significantly ( 5.88 ± 1.68, and 8.75 ± 3.44 nM respectively) (p<0.05) while CVC significantly increased to 38.90 ± 1.37 and 60.32 ± 1.95 %peak respectively (p<0.05). The low threshold of dilation (35°C) points to a possible role for the TRPV3 channels in the dilator response. However, the reduction in [ATP]d indicates that the dilator response is not likely due to ATP acting as a vasodilator substance.
The Role of Plasma Angiotensin II in Orthostatic Intolerance during Heat Stress Conditions
Authors: Harrison Michelle L. , Lee Josh F. , Brown Skyler , Brothers R. Matthew
Published: June 2021

An increase in internal temperature renders individuals more susceptible to syncope during a simulated hemorrhage challenge relative to during normothermia but the extent of this susceptibility varies amongst individuals. The objective of this study was to investigate the role of plasma angiotensin II (AngII) in this interindividual variability. This study tested the hypothesis that individuals with the greatest reduction in orthostatic tolerance between normothermic and heat stress conditions would have the smallest heat‐stress induced increase in plasma AngII. On separate days, 10 individuals were subjected to a maximal simulated hemorrhage challenge via a lower body negative pressure (LBNP) protocol. One trial was conducted under normothermic conditions and the other under hyperthermic conditions, following a 1.5 °C increase in internal temperature. Tolerance was quantified as cumulative stress index (CSI); calculated by summing the product of the LBNP and the time at each level until the test was terminated (i.e., 10 mmHg × 3 min + 20 mmHg × 3 min + 30 mmHg × 3 min, etc.). There was no correlation between the difference in CSI and the increase in plasma AngII from normothermic to heat‐stress conditions (r=0.05, p>.05). These results indicate that plasma AngII does not play a role in the interindividual variability in the tolerance to a simulated hemorrhage challenge during heat stress.
Activation of 5HT1A receptors in the nucleus tractus solitarius contributes to blood pressure compensation with blood loss and peripheral chemoreflex responses in the presence of acidosis
Authors: Vantrease Jaime Erin , Dudek Nichole , Scrogin Karie
Published: June 2021

Caudal serotonin neurons and the 5‐HT1A receptor ( 1AR) agonist, 8‐OH‐DPAT, promote sympathetic‐mediated increases in cardiac output after blood loss. We hypothesize that the metabolic acidosis of hemorrhage activates serotonin neurons and 1AR in the nucleus tractus solitarius (NTS) to facilitate chemoreflex responses to carotid body hypoxia. Here, we tested ventilatory responses to hypoxic hypercapnia (10% O2, 5% CO2) and blood pressure responses to hemorrhage and subsequent 8‐OH‐DPAT administration in rats subjected to bilateral knockdown of the 1AR in the NTS. An adeno‐associated viral vector harboring a short hairpin RNA targeting the rat 1AR (1ARshRNA) or a scrambled shRNA (Scram) was injected into the caudal NTS of male Sprague Dawley rats. After 4 weeks, rats injected with the 1AshRNA (n=12) had lower cumulative minute ventilation during hypoxic hypercapnia vs. Scram‐injected rats (n=13, P<0.01). Rats injected with 1AshRNA (n=8) had a more rapid fall in blood pressure with blood loss and an attenuated blood pressure response to 8‐OH‐DPAT injection (30 nmol/kg, iv, P<0.01) vs. Scram‐injected rats (n=9). 1AshRNA injection decreased 1AR protein in the caudal NTS (−35%, P<0.05). Thus, the beneficial hemodynamic effect of 8‐OH‐DPAT and endogenous serotonin in hemorrhage is related to activation of 1AR in the NTS and possibly to facilitation of chemoreflex responses to hypoxia. Funded by AHA 10PRE4000023.
Type 1 Diabetes in young women is associated with decreased circulatory response to hypovolemic stress
Authors: Lindenberger Marcus , Lindström Torbjörn , Länne Toste
Published: June 2021

Objective

Diabetes is associated with hemodynamic instability, e.g. during anaesthesia. Young men with type 1 diabetes (DM‐1) have impaired circulatory response to hypovolemic stress. The effect of DM‐1 on cardiovascular response to hypovolemia in young women is unknown however.

Design and Methods

Lower body negative pressure (LBNP) of 30 cm H2O was used to create rapid hypovolemic stress in fifteen young women with DM‐1 as well as sixteen healthy women. Cardiovascular response and the compensatory mobilisation of venous capacitance blood (capacitance response) and net fluid absorption were measured with volumetric technique.

Results

Capacitance response was both reduced and developed slower in DM‐1, P < 0.01. Fluid absorption was almost halved in women with DM‐1, P < 0.01. Arterial vasoconstriction also developed slower in DM‐1, P < 0.05.

Conclusions

Young women with DM‐1 present with decreased as well as slower mobilisation of venous capacitance blood and decreased net fluid absorption that could make women with type 1 diabetes prone to hemodynamic instability. Cardiovascular autonomic neuropathy could play a role, but also differences in the venous circulation and microcirculation.
Daily Rhythm of Brain Oxidation
Authors: Haushalter Kristofer , Patel Hemal , Ali Sameh
Published: June 2021

Circadian variations in pro‐ and antioxidants, enzymes, and markers of oxidative stress such as malonedialdehyde have been reported. However, nothing is known about the source(s) of free radicals that trigger or modulate these periodic variations. Here we explore the sources and levels of Reactive Oxygen Species (ROS) in young animal brains. We employed synaptosomal and mitochondrial preparations to study neuronal ROS and to identify contributions by mitochondria and NADPH oxidase (Nox) isoforms. We used spin trapping electron paramagnetic resonance (EPR) spectroscopy and electrochemical biosensing to detect superoxide, hydrogen peroxide, hydroxyl radicals, and nitric oxide simultaneously. We also followed daily variations of protein expression and mRNA levels of Nox subunits in mouse brain. We detected daily rhythms of substrate‐specific oxygen consumptions by mitochondria and by Nox enzymes in parallel with ROS production in the same sample. These findings suggest that circadian ROS oscillation may be involved in the interplay between metabolism and higher‐brain functions.
Pseudomonas aeruginosa produce autoantibodies against HSP60 in rats
Authors: Havnes Marianne , Ahlén Catrine , Brubakk Alf , Iversen Ole-Jan
Published: June 2021

Skin and ear infections, primarily caused by Pseudomonas aeruginosa (P. aeruginosa) are recurrent problems for saturation divers, while infections caused by P. aeruginosa are seldom observed in healthy people outside saturation chambers. Cystic fibrosis (CF) patients suffer from pulmonary infections by P. aeruginosa and it has been demonstrated that CF patients have high levels of anti‐HSP60 compared to controls, probably induced by P. aeruginosa. The present study investigated whether rats immunized with P. aeruginosa produced autoantibodies against their own HSP60 and whether diving influenced the level of circulating anti‐ HSP60 antibodies.

Methods

Rats were randomly assigned to one of three groups. Group 1 and 3 were immunized with P. aeruginosa, every other week. Groups 2 and 3 were exposed to simulated air dives to 400 kPa (4 ata) with 45 min bottom time, every week for seven weeks. The amount of anti‐HSP60 rat antibodies in the serum was analyzed by ELISA.

Results

The immunized rats showed a significant increase in the level of autoantibodies against HSP60, while no autoantibodies were detected in the dived rats. The rats both immunized and dived show no significant increase in circulating autoantibodies against HSP60. A possible explanation may be that HSP60 is expressed during diving and that cross reacting antibodies are bound.
Increased bone mineral density in experienced SCUBA divers
Authors: Valic Zoran , Bozic Josko , Kurir Tina Ticinovic , Novak Anela , Supe-Domic Daniela , Valic Maja
Published: June 2021

Weightlessness during prolonged water activities and bubble formation during decompression phase of SCUBA diving could influence bone structure of the diver. Previous research has reported controversial results in bone mineral density (BMD) in SCUBA divers, showing both decrease and no change in BMD. We hypothesized that middle aged experienced divers will present greater decrease in BMD than younger divers investigated in previous studies. We tested 11 SCUBA divers whose mean age was 46.2±2.3 years (mean±SEM). On average, they were involved in SCUBA diving for 26 years performing 363 hours of diving annually. BMD was measured at the levels of lumbar spine and hip regions using dual energy X‐ray absorptiometry. BMD value for total lumbar spine was 1.233±0.034 g/cm2, and for total hip was 1.150±0.048 g/cm2. T scores were 1.4±0.3 and 0.9±0.3 for lumbar and hip regions, respectively. Z scores, considering subjects age, were 1.6±0.3 and 1.2±0.3 for lumbar and hip regions, respectively. Parathyroid hormone, estradiol, and testosterone levels were within normal range in all subjects. In conclusion, our results show that middle aged, experienced divers have increased BMD. Such increase is especially evident in their lumbar region. This study was supported by Croatian Ministry of Science, Education and Sports.
Neuroplasticity of CNS oxygen toxicity (CNS‐OT): increased risk of seizure due to hyperbaric preconditioning (PC) and kindling effect
Authors: Pilla Raffaele , Fiorelli Tina , Held Heather E. , Landon Carol S. , Dean Jay B.
Published: June 2021

CNS‐OT limits the use of hyperbaric O2 (HBO2) clinically and in military diving. We studied the effects of preconditioning (PCs) gas mixtures and dive/seizure history on the latency to seizure (LS) in 118 adult rats implanted with a radio‐transmitter to record EEGs. After ≥1 wk recovery, rats underwent: a) hyperoxic PC at 1‐ 2ATA in pure O2; b) hyperbaric normoxic PC at 2ATA using Heliox/Nitrox; and c) air PC at 1ATA (control) or 2ATA. All PC protocols were conducted 3x, followed 24hr after the last treatment by one dive to 5ATA to seizure. Hyperoxic PC did not provide neuroprotection against seizure, decreasing LS by 51% (2ATA O2) and 42% (1ATA O2). Hyperbaric normoxic PC (2ATA Nitrox/Heliox) decreased LS by 78/89%. Western blot analyses of rat hippocampi suggest that hyperbaric pressure per se (normoxia+inert gases) accelerate onset of CNS‐OT by downregulation of Early Growth Response‐1, an early response gene involved in neuroprotection from oxidative stress. Also, in the absence of PC, rats experiencing 1 seizure/wk over 3–5wk developed a kindling response to HBO2 compared to rats that experienced 1 seizure/wk over 2wk, causing a LS decrease of 74% (4 ATA) and 55% (5 ATA) due to kindling (ONR).
Baseline plasma cGMP levels correlates with breath hold capacity in competitive breath hold divers
Authors: Lindholm Peter , Schiffer Tomas A , Lundberg Jon O , Weitzberg Eddie
Published: June 2021

Breath‐hold (BH) duration depends on oxygen stores and consumption. Strong peripheral vasoconstriction and reduction in cardiac output (diving response) reduce oxygen consumption during apnea. A healthy reactive endothelium may be important for an efficient diving response. Endothelium‐derived nitric oxide (NO) is deeply involved in endothelial function and plasma cGMP is considered as a marker of endothelial NO synthase activity.

Objective

To evaluate the association between plasma cGMP and BH capacity in trained BH divers.

Methods

Nine BH divers performed BHs of maximal duration after inhalation to 80% of vital capacity. Oxygen consumption was evaluated with pulse oximetry (SpO2) and exhaled O2 fraction (EtFO2) at end of apnea. Baseline plasma cGMP was measured before and 10min after the apnea protocol.

Results

A strong positive correlation was found between baseline plasma cGMP levels and maximum BH duration (344±13 sec, R2=0.63, P=0.011), SpO2 at 4min (R2=0.53, P=0.026) and EtFO2 at breath‐holds aborted at 4min (R2=0.50, P=0.026). Mean plasma cGMP increased from 4.3±0.8 to 7,8±1.8nM as a result of the apnea protocol (P=0.024).

Conlusion

Baseline plasma cGMP predicts breath hold capacity and oxygen consumption during apnea in trained breath hold divers. This indicates that endothelial NOS activity could be important in the vascular part of the diving response.
Adenosine A1‐receptor agonist (CHA) produces a hypothermic state by reducing BAT thermogenesis
Authors: Tupone Domenico , Madden Christopher J. , Algwaiz Haya , Morrison Shaun F.
Published: June 2021

Hibernating animals can reduce their energy expenditure by suspending thermogenesis in brown adipose tissue (BAT) and from shivering, despite marked falls in skin and core temperatures. Icv injection of the adenosine A1‐receptor agonist, N6‐cyclohexyl‐adenosine (CHA), produces a hypothermic state and induces hibernation in hibernating animals and hypothermia in rats on a calorie‐restricted diet. We investigated the potential for icv CHA to induce hypothermia in rat and whether inhibition of both BAT and shivering thermogenesis would contribute to the fall in body temperature. In Inactin‐anesthetized, Wistar rats, icv CHA (1mM, 10μl) decreased core, skin and BAT temperatures, reduced expired CO2, heart rate, BAT sympathetic nerve activity (SNA) and shivering EMG activity. In awake rats in a 15°C ambient, a similar icv injection of CHA decreased BAT temperature and induced a sleep‐like state, in contrast to icv injection of saline vehicle which had no effect on BAT temperature or observed behavioral state. We conclude that central adenosine A1‐receptor stimulation can produce hypothermia in the rat and that inhibition of BAT and shivering thermogenesis contributes to this marked reduction in core temperature. Supported by NIH grant NS40987.
Pontine μ‐opioid receptors mediate the bradypnea caused by clinically relevant rates of intravenous remifentanil in dogs
Authors: Prkic Ivana , Mustapic Sanda , Radocaj Tomislav , Stucke Astrid G. , Stuth Eckehard A. , Hopp Francis A. , Dean Caron , Zuperku Edward J.
Published: June 2021

Life‐threatening side effects such as profound bradypnea or apnea and variable upper airway obstruction limit the use of opioids for analgesia. It is yet unclear which sites containing mu‐opioid receptors (MORs) within the respiratory control network are responsible. The purpose of this study was 1) to define the pontine region in which MOR agonists produce bradypnea and 2) to determine whether antagonism of those MORs reverses bradypnea produced by IV remifentanil (remi; 0.1–1.0 μg/kg/min). The effects of microinjections of agonist [D‐Ala2, N‐Me‐Phe4, Gly‐ol5]‐enkephalin (DAMGO; 100 μM) and antagonist naloxone (NAL; 100 μM) into the dorsal rostral pons on the phrenic neurogram were studied in a decerebrate, vagotomized, ventilated, paralyzed canine preparation during hyperoxia. A 1‐mm grid pattern of microinjections was used. The DAMGO sensitive region extended from 5–7 mm lateral of midline and from 0–2 mm caudal of the inferior colliculus at a depth of 3–4 mm. During remi‐induced bradypnea (71.5±3.6% reduction in breathing rate; 21 dogs) NAL microinjections (860±69 nl each) within the region defined by the DAMGO protocol were able to reverse bradypnea (47.2±5.2%/injection) with 13 of 84 injections producing complete reversal. Histological examination of dye injections shows that the sensitive region corresponds to the parabrachial Kölliker‐Fuse complex. Supported by VA Medical Research Funds.
Postsynaptic modulation of nucleus tractus solitarius neurons in response to Prostaglandin E2
Authors: Gresham Ken , Mayer Catherine , Martin Richard J , Wilson Christopher G
Published: June 2021

Prostaglandin E2 (PGE2), produced in response to proinflammatory cytokines, can alter synaptic activity within the nucleus tractus solitarius (nTS) by altering glutamate release from vagal afferent terminals. Modulation of activity within the nTS alters signaling to other regions of the brainstem, including the regions responsible for respiratory rhythm generation. We hypothesized that PGE2 can alter the membrane properties of postsynaptic neurons within the nTS. Using whole‐cell patch‐clamp recording, we measured membrane voltage (VM) in response to injected current ramps in nTS neurons. We observed a decrease in maximum spike frequency after PGE2 application (19.6% decrease compared to control; n=3). The cells showed a decrease in both holding membrane potential (VH, 92.0% of control) as well as a decrease in the membrane potential threshold for spike firing (Vt, 92.6% of control). The chord resistance, Rchord = (Vh – Vt)/It, where It is the threshold current that elicits action potentials in the ramp protocol, showed a variable response in the three neurons recorded. Our data suggests that PGE2 is able to modulate postsynaptic neurons within the nTS through an undetermined mechanism.
Signaling pathways underlying the P2Y1 receptor‐mediated excitation of the preBötzinger Complex (preBötC) inspiratory rhythm generating network in vitro
Authors: Rajani Vishaal , Zwicker Jennifer D , Panaitescu Bogdan , Alvares Tucaaue S , de Chaves Elena Posse , Ballanyi Klaus , Funk Gregory D
Published: June 2021

The ventilatory response to hypoxia comprises an initial increase in ventilation followed by a secondary depression. The release of ATP within the respiratory network, including the preBötC, attenuates the depression, in part via a P2Y1 receptor (R), preBötC mechanism involving neurons and glia. To characterize the signaling pathways underlying the P2Y1 excitation, we used primary cultures of preBötC astrocytes loaded with Fluo‐4 and compared the fluorescence response evoked by ATP (10 μM) in control and after bath application of carbenoxolone (CBX, gap junction blocker 100 μM) and membrane permeant 2nd messenger blockers. CBX had no effect but U73122 (phospholipase C antagonist) and thapsigargin (depletes intracellular Ca2+(Ca2+ i) stores) blocked ATP‐evoked Ca2+i increases. In rhythmic medullary slices from neonatal rat, CBX had no effect on the frequency (f) response evoked by ATP (100 μM, 10 sec) in the preBötC. To test the role of Ca2+i we compared the f response to MRS2365 (P2Y1R agonist, 100 μM) before and after application of EGTA‐AM (1 mM) into the preBötC. EGTA reduced the control, 2.2±0.3 fold MRS2365 f increase by 64±7%. Response duration fell to 35±6% of control. In cultured preBötC glia, ATP‐evoked Ca2+i increases reflect PLC‐induced release from intracellular stores. In the preBötC, increases in Ca2+i contribute to the P2Y1‐evoked frequency increase. Supported by CIHR, WCHRI, AIHS & ALA.
Erythropoietin and its antagonist regulate the hypoxic fictive breathing in newborn mice
Authors: Soliz Jorge , Khemiri Hanan , Seaborn Tommy
Published: June 2021

Erythropoietin (Epo) in adult mouse interacts with the major brainstem centers associated with respiration to enhance the ventilatory response to acute and chronic conditions of physiological hypoxia (e.g. as occuring at high altitude). However, whether Epo is as well implicated in the regulation of breathing in newborns remains unknown. To answer this question en bloc brainstem‐spinal cord preparations were obtained from mice at postnatal day 4 (P4). After time‐ (30, 60 or 90 min) and dose‐dependent (0, 25 or 250 U) incubation with or without Epo, en bloc preparations were superfused with artificial cerebrospinal fluid (aCSF) bubbled with normoxic or hypoxic gas mixtures. Subsequently, the electrophysiological fictive breathing produced by axons at the C4 ventral root was recorded. Our results show that upon hypoxic conditions Epo stimulates the neural hypoxic respiratory activity and improves the post hypoxic recovery. In addition, proof‐of‐concept experiments showed that soluble Epo receptor (sEpoR), the endogenous antagonist of Epo, dramatically decreases the neural hypoxic respiratory activity. These results imply that Epo and its endogenous antagonist in P4 mice are implicated in the modulation and maintenance of respiratory motor output during hypoxic and post‐hypoxic challenges. As Epo is a highly promising protective therapeutic agent for several brain diseases, these results suggest that Epo applications may be also relevant for neuronal‐related respiratory disorders in term and preterm neonates.
Intermittent Fasting After Spinal Cord Injury Does Not Improve the Spontaneous Recovery of Baroreflex Regulation in the Rat
Authors: Zahner Matthew R.
Published: June 2021

Modest recovery of somatic function after incomplete spinal cord injury (SCI) has been widely demonstrated. Recently we have shown that spontaneous recovery of baroreflex regulation (BR) in rats also occurs. Dietary restriction in the form of every other day fasting (EODF) has been shown to have beneficial effects in the recovery of motor function after SCI. The goal of this study was to determine if EODF augments the spontaneous recovery of BR after chronic, left thoracic (T8) surgical spinal hemisection. To determine this, BR tests were performed on either ad‐lib fed or EODF rats either 1 week or 8 weeks after left, T8 spinal hemisection, or a sham lesion. During BR testing in sham lesioned rats, EODF had no effect on BR compared to rats fed ad‐lib. Therefore, data from these rats were merged into one sham lesioned group. In rats in which BR testing was performed 1 week after spinal hemisection, BR was significantly impaired (P < 0.05) in the ad‐lib but not the EODF rats compared to that of the sham lesioned group. However, in rats in which BR testing was performed 8 weeks after spinal hemisection, EODF did not significantly augment the recovery of BR. While there is evidence to suggest that EODF has beneficial effects on the recovery of motor function in rats, data from this study suggest that although after 1 week EODF appears to improve BR, over the course of 8 weeks EODF does not improve the spontaneous recovery of BR in the rat.
Heterogeneity in arm and leg vasoconstrictor responses to spontaneous bursts of resting muscle sympathetic nerve activity in humans
Authors: Fairfax Seth T , Padilla Jaume , Davis Michael J , Fadel Paul J
Published: June 2021

Sympathetic vascular regulation depends on the effectiveness of peripheral vessels to respond to muscle sympathetic nerve activity (MSNA). Greater α1‐adrenoceptor responsiveness has been reported in the human leg compared to the arm. However, whether these underlying receptor differences alter limb vascular responsiveness to MSNA is unknown. To begin to address this, we examined arm and leg vascular conductance responses to spontaneous MSNA bursts. Arterial pressure (Finapres), MSNA (microneurography) and simultaneous blood flows in the brachial (BA) and common femoral (CFA) arteries (duplex Doppler ultrasound) were continuously measured during 20 minutes of supine rest in 8 young men. Beat‐by‐beat changes in conductance for each vessel were characterized for 15 cardiac cycles following each individual MSNA burst using signal averaging to identify the temporal conductance pattern and a peak response was calculated. CFA conductance significantly decreased following MSNA bursts, reaching a nadir (−7.6±1.7%, p<0.05 vs. baseline) in ~8 cardiac cycles. In contrast, BA conductance initially increased (peak: +7.0±1%, p<0.05) and subsequently decreased (nadir: −1.4±1.3%, p>0.05) after ~8 cardiac cycles. These preliminary findings suggest heterogeneity between the arm and leg in the acute vascular responses following individual bursts of MSNA. Supported by RO1 HL093167
Disruption of social bonds in male prairie voles negatively influences behavioral, cardiac, and autonomic function
Authors: McNeal Neal , Scotti Melissa-Ann L. , Wardwell Joshua , Trahanas Diane M. , Dave Parag , Pinkepank Brett , Chandler Danielle L. , Bates Suzanne L. , LaRocca Meagan , Grippo Angela J.
Published: June 2021

The disruption of social bonds can have an adverse impact on emotional and cardiovascular health. The present study investigated the behavioral, cardiac (heart rate, HR; and heart rate variability, respiratory sinus arrhythmia, RSA), and autonomic nervous system (ANS) consequences of acute disruption of social bonds between male and female prairie voles. Adult male prairie voles were implanted with a wireless radiofrequency transmitter for electrocardiographic recordings. Following recovery, all male prairie voles were paired with a novel adult female; after 5 days, half of the males were separated from the female partner, while the other half remained paired (control). 5 days following the separation, male prairie voles were exposed to a forced swim test (FST). 48 hours following the FST, ANS function was assessed using pharmacological receptor blockade. The isolated male prairie voles displayed higher resting HR and lower RSA vs. controls. Isolated male prairie voles displayed depression‐relevant behavior and increased HR during the FST. Pharmacological ANS blockade yielded changes in HR indicative of ANS imbalance in the isolated group. The current findings provide insight into the underlying neurobiological mechanisms linking social environment disruptions to an increased risk of depression and cardiovascular dysfunction. Support: MH077581, NIU Graduate College
Angiotensin II Type 1A Receptors in the Brain Mediate the Effects of the Brain RAS on Fluid Balance in the DOCA‐salt Model
Authors: Hilzendeger Aline M , Grobe Justin L , Mark Allyn L , Sigmund Curt D
Published: June 2021

Angiotensin within the brain is required for the polydipsia and hypertension induced by DOCA‐salt (50 mg s.c. pellet, ad lib. 0.15 M NaCl), though the receptors and nuclei involved are unclear. Male mice homozygous for a floxed allele of the AT1AR gene were administered an adenovirus centrally (ICV) encoding either Cre‐recombinase and eGFP (AdCre; n=7), or eGFP alone (AdGFP; n=4). Measurements were first performed at baseline and after virus injection, and then after three weeks of DOCA‐salt treatment. Before DOCA, AdCre caused trends toward reduced total fluid (AdGFP 3.8±0.3; AdCre 2.7±0.4 mL/day) and total sodium (0.57±0.05; 0.47±0.03 mEq/day) intake, and reduced dipsogenic responses to overnight dehydration (AdGFP 0.09±0.001; AdCre 0.06±0.001 mL/2hr, P<0.01). Then, AdCre significantly attenuated the water (15.7±2.3; 8.2±1.8 mL/day, P<0.05) and sodium (1.6±0.4; 1.1±0.3 mEq/day, P<0.05) intake effects of DOCA. AdCre reduced AT1AR mRNA in the subfornical organ (SFO; 1.0±0.7; 0.4±0.3 fold, P<0.05), without significant effect in the PVN, ARC or cortex. Cre‐mediated recombination of genomic DNA was detected in the SFO after AdCre but not AdGFP. These data highlight involvement of brain AT1AR in hydromineral balance. Ongoing work is aimed at measuring the blood pressure effects of brain AT1AR modulation, and site‐specific targeting of the viral vectors to individual brain nuclei. Supported by the NIH and AHA.
Does ATPγS potentiate the muscle chemoreflex response to lactic acid?
Authors: Stone Audrey J , Yamauchi Katsuya , Leal Anna K , Kaufman Marc P
Published: June 2021

Birdsong et al. (2010) found that acute exposure to ATP potentiated ASIC evoked currents from dorsal root ganglion cells innervating muscles of rats. This finding prompted us to determine whether the results seen in vitro would translate to an in vivo preparation. We measured the pressor and cardioaccelerator responses to injecting lactic acid (24mM; 0.4mL), an ASIC agonist, into the femoral artery of decerebrated rats with either freely perfused hindlimbs (n=6) or hindlimbs whose femoral artery was ligated (n=5). This was done both before and after injecting ATPγS (200μg/kg). In freely perfused rats, the pressor response to lactic acid after ATPγS was not different from that to lactic acid before ATPγS (15±2 vs. 14±2 mmHg; p>0.05). The cardioaccelerator response to lactic acid after ATPγS was modestly greater than that evoked by lactic acid before ATPγS (3±1 vs. −2±1 bpm; p<0.05). In ligated rats, the pressor response to lactic acid was greater after ATPγS than before, although the increase was not significant (28±6 vs. 21±4 mmHg; p=0.11). The cardioaccelerator response to lactic acid after ATPγS was not significantly different from that evoked by lactic acid before ATPγS (1±2 vs. 2±2 bpm; p>0.05). We conclude that ATPγS does not potentiate the muscle chemoreflex response to lactic acid but may do so in rats with ligated femoral arteries. Supported by NIH RO1‐HL030710 and P01 HL096570.
Repeated Restraint Stress Increases Baseline Blood Pressure in Spontaneously Hypertensive Rats
Authors: McCowan Michael L , Erdos Benedek , Cho Namjik , Sumners Colin , Scheuer Deborah A
Published: June 2021

Chronic moderate stress contributes to hypertension in susceptible humans, but this has proven difficult to model in animals. Spontaneously hypertensive rats (SHR) become hypertensive with age and have exaggerated responses to psychological stress. We hypothesized that SHR would be susceptible to chronic moderate stress‐induced hypertension. Arterial pressure was measured by radiotelemetry in control (n=8) and chronically stressed (1hr restraint stress per day during the light period, 6 days a week for 4 wks, n=8) SHR. The average increases in mean arterial pressure (MAP) during restraint was not significantly different (P=0.09) on the first (35±3 mmHg) and final days (32±3) mmHg of restraint. Baseline MAP during the dark period, not directly influenced by stress responses, was elevated in both control and stressed rats with time, but the increase was significantly greater (P<0.05) in the stressed (12±2 mmHg) compared with the unstressed (4±1 mmHg p<0.05) rats. In contrast, nighttime heart rate was not affected by chronic stress. Parallel with the elevation in MAP, preliminary data indicate that microglia activation within the paraventricular nucleus of the hypothalamus increased significantly in stressed rats, suggesting involvement of neuroimmune mechanisms in stress‐induced hypertension. Supported by NIH #HL93186 (MPI)
Leptin increases baroreflex gain: role of melanocortin 3/4 receptors in the hypothalamic paraventricular nucleus
Authors: Li Baoxin , Cassaglia Priscila A. , Brooks Virginia L.
Published: June 2021

Intracerebroventricular (ICV) leptin increases lumbar sympathetic nerve activity (LSNA) and LSNA baroreflex gain (BRG), but the sites and neuronal pathways are unknown. To test the role of the paraventricular nucleus (PVN), baroreflex function was assessed in α‐chloralose anesthetized male SD rats at baseline and 1 hr after ICV leptin (3 μg), using a 4 parameter sigmoidal fit of LSNA responses to slow ramp (3–5 min) changes in arterial pressure, induced by iv infusion of nitroprusside and phenylephrine. Then, 90 min after ICV leptin, 60 nL of muscimol (mus; 1 mM/L; n=3), the melanocortin 3/4 receptor (MC3/4R) inhibitor SHU9119 (0.5 mM/L; n=6), or the aCSF vehicle (n=5) was microinjected bilaterally into the PVN. Leptin increased (P<0.05) LSNA (158±9%) and LSNA BRG (from 3.2±0.4 to 5.7±0.2 %/mmHg). In control experiments (after PVN aCSF), further increases (P<0.05) in LSNA (186±21%) and LSNA BRG (7.2±0.6 %/mmHg) were observed. In contrast, PVN inhibition with mus completely reversed (P<0.05) the effects of leptin to increase LSNA [to 160±9% (leptin) then 125±2% (mus)] and LSNA BRG [in %/mmHg: from 3.4±0.6 to 4.8±0.6 (leptin) then 3.6±0.4 (mus)]. PVN SHU9119 decreased (P<0.05) LSNA [to 169±9% (leptin) then 139±10% (SHU9119)] and LSNA BRG [in %/mmHg: from 3.1±0.4 to 4.8±0.7 (leptin) then 4.4±0.6 (SHU9119)] compared to aCSF; however, both LSNA and LSNA BRG remained elevated (P<0.05) versus baseline. In conclusion, the PVN contributes to the increases in LSNA and LSNA BRG induced by ICV leptin, in part via MC3/4R. Support: HL088552.
Cholecystokinin Antagonizes Opioid Function during Electroacupuncture Modulation of Reflex Hypertension in Rats
Authors: Li Min , Tjen-A-Looi Stephanie C. , Choi Emma , Xu Zheyan , Ho Jesse , Longhurst John C.
Published: June 2021

Hypertension is one of the greatest causes of death in middle‐aged and elderly North Americans, but current western medical therapies are not fully effective. Acupuncture or electroacupuncture (EA) is increasingly being accepted as a viable therapy in the United States and may serve as an alternative treatment to drug therapy in patients with mild to moderate hypertension. We have demonstrated that EA acts through an opioid mechanism in rostral ventrolateral medulla (rVLM) to inhibit sympathoexcitatory reflexes induced by gastric distention. Cholecystokinin octapeptide (CCK‐8), a gastrointestinal peptide hormone, is present throughout the central nervous system and mediates pain and anxiety. CCK‐8 interacts with CCK1 and CCK2 receptors. The present study investigated the hypothesis that CCK‐8 in the rVLM limits the modulatory action of EA effect on sympathoexcitatory responses. Experiments were performed on male rats anesthetized with ketamine and α‐chloralose who were subjected to repeated gastric distension every 10 minutes. EA ( 2Hz, 0.5ms, 1–4mA) at Jianshi‐Neiguan (P5–P6) acupoints was applied for 30 min followed by microinjection of CCK‐8 (0.15mM, 50 nl) into the rVLM in 7 rats reversed the EA modulatory response from (11.0 ± 2.0 ) to (19.1 ± 2.8) mmHg. Saline injections into the rVLM at the end of 30 min EA did not influence the prolonged inhibition of reflex elevations in blood pressure in five other animals. Alternatively, devazepide (0.5 mM, 50 nl), a CCK1 antagonist microinjected into the rVLM of six rats that initially did not respond to 30 min of EA led to conversion during a second application of EA. Micoinjection of the vehicle of devazepide (50 nl ) into rVLM did not modify the nonresponsiveness to EA application (n=2). These data suggest that CCK‐8 through its action on CCK1 receptors limits the action of EA in the rVLM of rats in modulating reflex hypertension. (Supported by AHA 10POST4190125, NIH HL‐63313 and HL‐072125).
Photostimulation of caudal C1 catecholaminergic neurons reduces arterial pressure and heart rate
Authors: Madden Christopher J.
Published: June 2021

Caudal C1 catecholaminergic neurons in the ventrolateral medulla (VLM) between ~13.5 – 14 mm caudal to bregma were infected with a lentiviral‐vector containing channelrhodopsin‐2 and mCherry, under the control of the Phox2‐responsive promoter PRSx8. Immunohistochemical localization of mCherry in the efferent fibers and terminals of these C1 neurons demonstrates projections to the rostral raphe pallidus (rRPa), the nucleus tractus solitarius, the rostral VLM, the hypothalamus (including the PVH and DMH) and the preoptic area. In urethane/chloralose anesthetized rats (n=5) photostimulation (473nm, 10ms, 8–15mW) of these C1 neurons decreased mean arterial pressure (MAP) and heart rate in a laser pulse frequency‐dependent manner, with 40Hz stimulation producing a maximal depressor responses of −21 ± 6 mmHg and a bradycardia of −111 ± 7 bpm. The decrease in MAP was attenuated by nanoinjection of idazoxan (IDZ, 6nmol in 100 nl), in the rRPa (post‐IDZ, 40Hz: −6 ± 4 mmHg), whereas the bradycardia was not affected by idazoxan in the rRPa (post‐IDZ, 40Hz: −108 ± 25 bpm). The depressor response to activation of caudal C1 neurons may have arisen from activation of alpha2 receptors in rRPa leading to inhibition of cutaneous vasoconstriction and a reduction in total peripheral resistance. However, the role of other projection targets of caudal C1 neurons in the evoked depressor response and bradycardia are being explored. Supported by: NIH grants NS040987 (Shaun F. Morrison), DK082558 (CJM) and an American Heart Association Scientist Development Grant (CJM).
The dopamine D3 receptor knockout mouse models aging‐related changes in hypertension and cardiac fibrosis
Authors: Lust Robert , Keeler Benjamin E. , Johnson Tracy , Jones Christopher , Tulis David A. , Virag Jitka A. , Clemens Stefan
Published: June 2021

The increased prevalence of hypertension with aging is well established, as is a role for the dopamine D3 receptor in the general pathophysiology of hypertension. To determine the specific effects of D3 dysfunction on autonomic output and cardiac involvement in aging associated hypertension, non‐invasive blood pressure measurements, echocardiography, and histochemistry were used to compare cardiac structure and function in differently‐aged wild‐type (WT) animals (10 weeks, 1 year, 2 year) and D3 receptor knockout mice (D3KO). In WT animals, aging‐related increases in blood pressure and cardiac function, accompanied by bradycardia in the oldest animals were observed. Intriguingly, 2 month‐old D3KO mice displayed blood pressure and heart rate values that were significantly increased over their age‐matched WT controls, and that were comparable to those of the 2 year‐old WT group. Echocardiography did not reveal significant differences between age matched young WT and D3KO mice, but immunohistology demonstrated fibrosis in the young D3KO mice that was comparable to the age‐related fibrosis seen in 2 year old WT mice. Taken together, these data suggest that the D3KO animal may serve as a model to better understand the role of the dopamine D3 receptor in the aging heart, and in particular its role in the pathophysiology of cardiovascular fibrosis. Funded by Brody School of Medicine (SC), and NIH NHLBI HL081720 (DAT).
Fish oil and sympathetic nerve activity in normotensive and prehypertensive humans
Authors: Schwartz Christopher E , Joyner Michael J , Yang Huan , Carter Jason R
Published: June 2021

The antihypertensive influence of fish oil is controversial, and mechanisms remain unclear. We tested the hypothesis that fish oil reduces mean arterial pressure (MAP) via reductions in muscle sympathetic nerve activity (MSNA). Because the inverse relation between fish oil and hypertension appears to be dependent on the degree of hypertension, we also tested the hypothesis that fish oil would elicit more dramatic reductions in MAP and MSNA in prehypertensive (PHT) compared to normotensive (NT) subjects. Resting MAP, MSNA, and heart rate (HR) were examined before and after 8 wk of fish oil (9g/day) or placebo (olive oil; 9g/day) in 38 NT (19 fish oil; 19 placebo) and 29 PHT (15 fish oil; 14 placebo) volunteers. Fish oil did not alter resting MAP, MSNA, or HR in either NT (71±2 to 71±2 mmHg; 11±2 to 10±1 bursts/min; 80±1 to 80±1 beats/min) or PHT (88±2 to 87±1 mmHg; 11±2 to 10±2 bursts/min; 73±2 to 73±2 beats/min) subjects. However, when NT and PHT groups were consolidated, a significant correlation was observed between changes in MAP and changes in MSNA in the fish oil group (r=0.354, p=0.035). In conclusion, fish oil did not alter neural cardiovascular control in NT or PHT. However, interindividual MAP responses to fish oil appear to be moderately associated with changes in MSNA, suggesting that the sympathetic nervous system may contribute to the inconsistent antihypertensive response of fish oil. Supported by NIH (HL‐088689).
Aldosterone induces Cardiomyocyte Hypertrophy in vitro and in vivo via Interleukin‐18
Authors: Pankey Edward A. , Murthy Subramanyam N. , Bysani Ramakrishna V. , Kadowitz Philip J. , Valente Anthony J.
Published: June 2021

Aldosterone (Aldo), a component of the Renin‐Angiotensin‐Aldosterone system, plays a critical role in myocardial hypertrophy, remodeling and failure. Since the pro‐inflammatory cytokine interleukin (IL)‐18 is an inducible pro‐hypertrophic factor, we investigated whether Aldo‐induced cardiomyocyte hypertrophy is IL‐18 dependent. Aldo (50 nM) induced cell hypertrophy and IL‐18 mRNA and protein expression in cultured adult mouse cardiomyocytes. These effects were significantly inhibited by pre‐treatment with the mineralocorticoid receptor (MR) blocker spironolactone, IL‐18 neutralizing antibodies, or IL‐18BP. Aldo induced NF‐κB and AP‐1 DNA‐binding activities and reporter gene activation, and phosphorylation and nuclear translocation of p65 and c‐Jun. Mutation of the NF‐κB and AP‐1 binding sites in an Il18 promoter reporter construct blocked Aldo‐induced luciferase activity. Treatment with DPI, knockdown of NOX2, or forced expression of dnp65 and dnc‐Jun all blunted Aldo‐induced IL‐18 expression and cardiomyocyte hypertrophy. Further, Aldo‐induced hypertrophy was markedly attenuated in cardiomyocytes isolated from IL‐18 null and IL‐18BP Tg mice. In vivo, continuous infusion of Aldo (1 mg/Kg/day, s/c) for 21 days upregulated IL‐18 mRNA and protein expression, and induced myocardial hypertrophy without significantly altering systolic blood pressure. Co‐administration of spiranolactone markedly attenuated these effects. Notably, Aldo‐induced myocardial hypertrophy was significantly reduced in IL‐18 null and IL‐18BP Tg mice. These results demonstrate that Aldo‐induced cardiomyocyte hypertrophy is mediated through a NOX2/ROS‐dependent IL‐18 induction pathway. Targeting IL‐18 has the therapeutic potential in myocardial hypertrophy and adverse remodeling.