bluuebunny/crossref_metadata_2025 huggingface dataset:
Aging induced additional impairment in cardiovascular control in ovariectomized rats
Authors: Dias Danielle Silva , Bernardes Nathalia , Barboza Catarina , Sanches Iris Callado , Irigoyen Maria-Cláudia , De Angelis Kátia
Published: June 2021

The objective was to investigate the effects of aging on cardiovascular parameters in females rats submitted to ovarian hormones deprivation. Female Wistar rats were divided into 4 groups (n=8 each group): young adult (2–3 mo, YA), aged (18 mo, AG), young adult ovariectomized (YA‐OVX) and aged ovariectomized (AG‐OVX). Arterial pressure (AP) and heart rate (HR) signals were directly recorded in conscious rats. The baroreflex sensitivity (BRS) was evaluated by tachycardic (TR) and bradycardic (BR) responses. The ovariectomy, associated or not with aging, induced increase in AP values (YA‐OVX: 124±1.35 and AG‐OVX: 136±7.06 vs. YA: 112±2.56 mmHg). There was an additional AP increase in AG‐OVX in relation to YA‐OVX and AG rats (120±2.6 mmHg). The HR was enhanced in AG, YA‐OVX, AG‐OVX when compared with YA group. The BR and TR were impaired in AG (0.83±0.06 and 1.50±0.28 bpm/mmHg) as compared to YA group (1.27±0.08 and −3.70±0.30 bpm/mmHg). Ovariectomy (YA‐OVX: 1.09±0.08 and 2.11±0.21 and AG‐OVX: 0.54±0.05 and −0.88±0.33 bpm/mmHg) decreased both BR and TR in relation to YA and AG groups. Furthermore, BRS was additionally reduced in AG‐OVX as compared to YA‐OVX rats. These results demonstrated that the ovarian hormone deprivation impact on arterial pressure and BRS is aged dependent.
Involvement of the Median Preoptic Nucleus in the arterial blood pressure regulation
Authors: Silveira Ludmila Lima , Silva Elaine Fernanda , Silva Rúbia Nara , Rosa Daniel A , Pedrino Gustavo Rodrigues
Published: June 2021

Studies have been shown that Median Preoptic Nucleus (MnPO) neurons have a great influence in the cardiovascular responses induced by changes in circulating volume. The present study sought to determine the participation of MnPO in the cardiovascular control. Male Wistar normotensive (NT) and spontaneously hypertensive (SH) rats (280–320g) were anesthetized with urethane (1.2 g/kg, i.v.) and instrumented for mean arterial blood pressure (MAP) and renal blood flow (RBF) recordings. Renal vascular conductance (RVC) was calculated as the ratio RBF/MAP and expressed as percentage of baseline. In NT rats (n=7), inhibition of MnPO nucleus produced a significant hypotension (−7 ± 1.5 mmHg) and renal vasodilation (5.3 ± 1.2% above baseline). In SH rats (n=8), hypotension response was significantly greater (−15 ± 2.7 mmHg, p<0.05) than NT rats. We also observed an increase of RVC (8.4 ± 2.4% above baseline) in HT rats. Analysis of the spread of dye nanoinjected at the end of the experiment showed that the drug injection sites were confined to the MnPO. We conclude that the MnPO nucleus is involved in the tonic regulation of blood pressure in NT rats. Moreover, the increase of neuronal activity in the MnPO may contribute to sympathoexcitation and maintenance of hypertension in SH rats. Supported by CNPq (477832/2010‐5; GRP).
The role of neurohypophysis in the long‐term blood pressure regulation in rats
Authors: Quintanar-Stephano Andrés , Contreras-Romo Martha Citlalli , Rodríguez-Peralta Adriana , González-Ruiz Claudia Rebeca , Reynoso-Andeola Irma Guadalupe , Ponce-Gallegos Raul , Kovacs Kalman
Published: June 2021

Evidence suggest that arginine vasopressin (AVP) may contribute to the development and/or maintenance of hypertension in humans and experimental animals. This is partially explained by the antidiuretic (increased vascular volume) and vasopressor effects (increased blood vessels resistance) of AVP. Here we propose that rats with long‐term low blood levels of AVP will cause increases in both; urine output and water intake and diminution of the mean blood pressure (MBP). Young male Wistar rats were divided in sham operated (SHAM) and neurointermediate pituitary lobectomized (NIL) (n=15 in each group). Water intake and urine output where measured once a week by placing the animals in a metabolic box. Five weeks after surgeries MBP was measured by an intra carotid catheter connected to a blood pressure transducer and a data acquisition system (BIOPAC Systems Inc.). AVP, Na+ and K+ serum levels were also measured. Results shown that as compared with SHAM group, NIL animals developed significant low AVP levels, no changes in Na+ and K+ levels and an initial increase in urine output and water intake (diabetes insipidus), to return to normality during second week. In NIL animals a significant diminution of MBP occurred: SHAM, 105±9.2 versus 65±6 mmHg of the NIL animals, p<0.001. These results suggest that neurohypophyseal AVP may be an important factor in the long‐term blood pressure regulation.
An afferent basis for sexual dimorphism in the aortic baroreceptor reflex of rat
Authors: Chavez Grace Santa Cruz , Li Bai-Yan , Schild John H.
Published: June 2021

Our lab has shown that that female rats have a unique and functionally distinct class of low threshold, myelinated (Ah‐type) aortic baroreceptors (BR) rarely observed in males. Here, we quantify the functional role of these afferents in the parasympathetic mediated reduction of mean arterial blood pressure (MAP). Aged‐matched populations of urethane and alpha‐chloralose anesthetized naive male (n=14) and female (n = 15) rats were studied using a common protocol for bipolar electrical stimulation of the left aortic depressor nerve. The impact upon the MAP of the left femoral artery was measured in response to selective, repetitive stimulation (1–100 Hz) of myelinated (A‐type) and unmyelinated (C‐type) BR fibers. Across both populations the magnitude of the depressor response (% reduction in MAP) was similar, but for one robust and highly repeatable exception. In male rats, nerve stimulation rates below ~10 Hz failed to elicit a significant depressor response until the stimulus magnitude was increased beyond the electrical threshold for unmyelinated C‐type BR. In female rats, however, stimulation rates below ~10 Hz elicited a marked reduction in MAP at intensities well below the electrical threshold for unmyelinated C‐type BR fibers. We contend that low threshold Ah‐type BR afferents provide, at least in part, a neurophysiological basis for the sexual dimorphism in neurocirculatory control. HL072012, HL081819
Sex‐specific effects of type 2 diabetes on autonomic function in coronary artery disease
Authors: Kiviniemi Antti , Hautala Arto J , Karjalainen Jaana , Piira Olli-Pekka , Lepojärvi Samuli , Tiinanen Suvi , Seppänen Tapio , Ukkola Olavi , Huikuri Heikki V , Tulppo Mikko P
Published: June 2021

Autonomic dysfunction is a potent factor increasing cardiac mortality in patients with coronary artery disease (CAD). However, the interaction of sex and type 2 diabetes (T2D) with autonomic function in CAD patients is not well‐known at modern treatment era. Spectral characteristics of R‐R interval and blood pressure (BP) oscillations and baroreflex sensitivity (BRS) were analyzed at supine rest and during passive tilt in 133 CAD patients with preserved ejection fraction (102 men, 52 T2D; 31 women, 14 T2D). The groups were matched according to age, ejection fraction and history of myocardial infarction. Sex*T2D interaction in response to tilt was assessed adjusting e.g. for exercise capacity, body mass index and CAD treatment. Sex*T2D interaction was observed in changes of diastolic BP (p=0.025) and BRS from rest to tilt (p=0.044). In women, decrease in diastolic BP was larger in CAD+T2D compared with CAD (−6±8 vs. 1±8 mmHg, p=0.022) but not in men (−3±7 vs. −3±8 mmHg, p=0.937). In women, decrease in BRS was larger in CAD+T2D compared with CAD (−1.3±3.6 vs. 1.5±8.5 ms/mmHg, p=0.024) but not in men (−3.2±3.2 vs. −2.8±5.9 ms/mmHg, p=0.488). Sex modifies the effects of T2D on autonomic responses to postural stress in CAD patients. TD2 impairs BP regulation particularly in CAD women. Supported by TEKES, Finland and Paavo Nurmi Foundation, Finland.
Interactions between endothelin‐1 and sympathetic nerve activity in normotensive humans
Authors: Hart Emma C , Joyner Michael J , Wallin B Gunnar , Curry Timothy B , Charkoudian Nisha
Published: June 2021

Previous data indicate that endothelin‐1 may have a direct excitatory effect on sympathetic nerve activity in animals and hypertensive humans. Whether this is true in normotensive humans is unclear. We investigated the relationship between endogenous endothelin‐1 and muscle sympathetic nerve activity (MSNA) in 15 normotensive young men and 15 women (age; 25 ± 1 vs. 25 ± 2 yrs, BMI; 25 ± 1 vs. 23 ± 1 kg/m2). MSNA was recorded via peroneal microneurography, arterial pressure was estimated from brachial arterial line and serum levels of endothelin‐1 (brachial artery) was measured by a quantitative two‐site chemiluminescent immunoassay. Mean arterial pressure (MAP, 90 ± 2 vs. 93 ± 2 mmHg), MSNA (37 ± 3 vs. 34 ± 4 bursts/100 heart beats) and endothelin‐1 (0.72 ± 0.03 vs. 0.63 pg/mL) were not different between men and women respectively. Interestingly, resting MSNA was positively related to arterial levels of endothelin‐1 in men (r = 0.69, P<0.05) but not in women (r = 0.03). Thus, men with high MSNA had high levels of endothelin‐1. These data suggest that endogenous endothelin‐1 is linked to tonic levels of sympathetic nerve activity in men but not in women. AHA 2170087 (ECJH); HL083947 (NC, MJJ, BGW); NIH RR024150 (CTSA).
Organ culture as an in vitro model for the study of dual‐specificity phosphatase‐5 (DUSP‐5) and myogenic response in rat cerebral arterioles
Authors: Gebremedhin Debebe , Wickramasekera Nadi T , Harder David R.
Published: June 2021

Increase in intravascular pressure causes depolarization and constriction of cerebral arteries. The molecular mechanism of pressure‐induced myogenic response remains obscure. Our goal was to provide an optimal time window and preserved vascular function for an organ culture of cerebral arteries for the study of mechanisms involved in the regulation of cerebral arterial function. We initiated a comparative study of cultured and freshly isolated cerebral arteries in response to elevated intravascular pressure, vasodilator and vasoconstrictor stimuli, activity of Ca2+‐activated K+ (KCa) single‐channel current and protein expression of CYP 4 and DUSP‐5 enzymes. The results indicate that 72 h time frame of organ culture of cerebral arteries maintains cellular integrity, pressure dependent constriction, CYP4A2 and 4F protein expression, endothelium‐dependent and independent dilations, KCa channel current activity and vasoconstrictor response to serotonin. Furthermore, using a permeabilization, transfection technique the 72 h cultured arteries elicited a gene specific siRNA induced knockdown of DUSP‐5 protein expression. Subsequent pressure myograph studies and inhibitor studies revealed role of DUSP‐5 in regulation of myogenic tone. We propose a possible mechanism by which DUSP‐5 and ERK regulate myogenic response in cerebral arterioles. RO1 HL033833, RO1 HL092105, T32 HL007792.
Chronic hypoxia differentially modulates age‐dependent responses of ovine middle cerebral arteries to VEGF
Authors: Silpanisong Jinjutha , Hubbell Margaret C , Pearce William Julian
Published: June 2021

To better understand how chronic hypoxia causes vascular remodeling, we hypothesized that hypoxic increases in VEGF alter cerebrovascular contraction through direct actions on both endothelium and arterial smooth muscle. Endothelium intact (E+) and denuded (E−) middle cerebral arteries (MCA) harvested from term fetuses and non‐pregnant adult sheep kept at sea level or 3820m for 110 days were serum starved 24h then cultured 24h with 0, 3, 10, or 30 ng/ml VEGF. All adult MCAs showed decreased K+ induced contractions with VEGF treatment, and E+ MCAs exhibited stronger K+ induced contractions than E− MCAs. VEGF produced a graded biphasic effect, negligible at 30 ng/ml in both E+ and E− normoxic adult MCAs. Fetal arteries exhibited little reactivity to VEGF. VEGF enhanced stretch‐induced contractions in E− normoxic adult MCAs, an effect absent at low concentrations in E+ normoxic and all hypoxic adult MCAs. Stretch‐induced contractions were generally greater in E− than in E+ arteries from both normoxic and hypoxic fetal MCAs. VEGF produced opposite biphasic effects on E+ and E− fetal arteries, of greater magnitude in normoxic than hypoxic arteries. These data support the hypothesis that VEGF can alter cerebrovascular contraction through direct actions on endothelium and arterial smooth muscle, thereby contributing to age‐dependent hypoxic cerebrovascular remodeling. Supported by P01‐HD31226.
Insulin‐induced hypertension in streptozotocin‐induced diabetic mice involves α1D‐adrenaline receptor‐mediated over‐contraction of the aorta and interlobar arteries
Authors: Nobe Koji , Hashimoto Terumasa , Honda Kazuo
Published: June 2021

Although insulin treatment is essential for diabetic patients, it often induces hypertension in these patients. To understand the mechanism involved, we treated streptozotocin (STZ; 200 mg/kg)‐induced diabetic mice (>400 mg/dL glucose) with 50 U/kg/day insulin (STZ+Ins) for 2 weeks. Systolic blood pressure (BP) was significantly higher (by 124%) in STZ+Ins mice than in untreated control mice, but not in mice treated with STZ or insulin alone. In terms of the mechanism for the increase in BP in STZ+Ins mice, we found that phenylephrine‐induced force development in the aorta and interlobar artery (ILA) was greater in STZ+Ins mice than in untreated control mice, whereas there were no differences in the force development in the mesenteric and renal arteries. Because contractions of the aorta and ILA are mediated via the α1D‐adrenaline receptor (AR), the study was repeated in α1D‐AR knockout (α1D‐KO) mice. The increase in BP induced by diabetes and insulin was suppressed in α1D‐KO mice. These results indicate that insulin increases BP, but only in the diabetic state, through a pathway involving α1D‐AR‐mediated aorta and ILA over‐contraction.
Prostaglandin E2 Activates Basal EP4 Receptors to Stimulate Chloride Secretion Via Both cAMP and Calcium Mediated Pathways
Authors: Rajagopal Madhumitha , Kathpalia Paru P , Pao Alan C.
Published: June 2021

The renal collecting duct (CD) maintains salt (NaCl) balance by fine‐tuning NaCl excretion in response to dietary salt intake. Under conditions of high dietary salt intake (HDS), prostaglandin‐E2 (PGE‐2) production is enhanced and promotes NaCl excretion. The molecular mechanisms by which PGE‐2 works are not well defined. Under conditions of HDS, Na+ reabsorption is suppressed, and the regulation of Cl− secretion may predominate. The initial segment of the inner medullary CD (IMCD) is the only segment known to secrete Cl− under HDS. We used the mIMCD‐K2 cell line, a mouse cell line derived from the initial IMCD, to study the effects of PGE‐2 on Cl− transport in the IMCD.

In mIMCD‐K2 cells, PGE‐2 activates basolateral EP‐4 receptors (EP‐4R) to increase Cl− secretion via both the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) and Ca2+ activated Cl− channels (CACC). EP‐4R activation enhances cAMP production which activates CFTR; unexpectedly, we found that EP4R activation also increases intracellular Ca2+ to stimulate CACC mediated Cl− secretion. We also determined that PGE‐2 stimulated secretion involves crosstalk between cAMP and Ca2+ signaling pathways in which intracellular Ca2+ influences CFTR activity and cAMP influences CACC activity. These two pathways, and the crosstalk between them, may represent a concerted mechanism by which PGE‐2 acts to enhance NaCl excretion under conditions of HDS.
Inhibition of NADPH Oxidase Attenuates Hyperhomocysteinemia‐induced NALP3 Inflammasome Activation in Mouse Glomeruli
Authors: Abais Justine , Boini Krishna , Xia Min , Li Pin-Lan
Published: June 2021

Our previous studies have shown that NALP3 inflammasome activation is importantly involved in podocyte dysfunction and glomerular sclerosis induced by hyperhomocysteinemia (hHcys). The present study was designed to test whether in vivo inhibition of NADPH oxidase (Nox)‐mediated redox signaling by administration of a gp91ds‐tat peptide attenuates hHcys‐induced NALP3 inflammasome activation in mouse glomeruli. Uninephrectomized C57BL/6J WT mice were fed normal chow or a folate free (FF) diet for 4 weeks to produce hHcys. Confocal microscopy showed increased inflammasome formation, demonstrated by increased colocalization between the 3 major inflammasome components NALP3, ASC and caspase‐1. Associated with such colocalization, hHcys also increased both renal caspase‐1 activity (1.5 folds) and IL‐1β production (2.1 folds) compared to the control mice. All of these hHcys‐induced changes were significantly blocked when mice were administered a gp91ds‐tat peptide. hHcys‐induced superoxide production was also considerably inhibited with the peptide by 57.3%. Furthermore, gp91ds‐tat treatment demonstrated in vivo renal protective effects, preventing proteinuria, albuminuria, and glomerular morphological changes induced by the hHcys. In addition, immunohistochemical staining showed that hHcys promoted glomerular infiltration of macrophages and T‐cells; however, this effect was not observed in mice simultaneously receiving gp91ds‐tat. These results confirm that Nox redox signaling may trigger hHcys‐induced NALP3 inflammasome activation and that inhibition of Nox indeed prevents the inflammatory response as shown by decreased immune cell infiltration in glomeruli (supported by NIH grants HL057244 and DK54927).
Disordered oxygen metabolism in early chronic kidney disease
Authors: Singh Prabhleen , Pham Hai , Sharik Meaghen , Murphy Anne , Petrosyan Susanna , Thomson Scott , Blantz Roland
Published: June 2021

Structural changes leading to chronic renal hypoxia, implicated in chronic kidney disease (CKD) progression, occur late and do not explain early intrarenal hypoxia. To examine the early functional adaptations that may increase oxygen demand leading to hypoxia, micropuncture and oxygen consumption (QO2) studies were conducted in rats 1 week after subtotal nephrectomy (STN).

Although, oxygen delivery (DO2) was lower in STN, renal oxygen extraction (arterial‐venous O2 content) doubled in STN vs. control (0.014 vs. 0.007, p<0.05). Both QO2 and (A‐V)O2 factored for GFR were significantly higher in STN. Single nephron GFR nearly doubled in STN vs. controls (p<0.05) contributing to transport related QO2 but could not explain the 3‐fold increase in QO2/nephron. Proximal reabsorption was lower in STN shifting salt reabsorption to distal sites associated with increased energetic costs. Expression of NADPH oxidase was also increased in STN. Mitochondrial QO2 revealed lower state3 respiratory capacity and respiratory control ratio (RCR) in STN, suggestive of mitochondrial complex I dysfunction seen in hypoxia. Treatment with hypoxia inducible factor (HIF) inducer, DMOG, significantly improved several parameters (p<0.05) including DO2, (A‐V)O2,(A‐V)O2/GFR, and mitochondrial state3respiratory capacity and RCR in STN. Major alterations in both mitochondrial and non‐mitochondrial QO2 in early STN, most of which were corrected with HIF induction.
DGC protects neuronal cells against glutamate‐induced oxidative injury through the induction of HO‐1 expression
Authors: Kim Jong-Sang , Park In-Sil , Kim Hyo Jung , Jung Chaelim , Lim Ji Sun , Lim Soon Sung
Published: June 2021

Oxidative stress has been related to the development of chronic neurodegenerative diseases and acute neurological injury. Licorice, the root of the Glycyrrhiza species (Glycyrrhiza uralensis Fisher), is known to have antioxidant, anti‐inflammatory, anti‐viral, and anti‐tumor properties. The object of this study is to explore the neuroprotective effects of dehydroglyasperin C (DGC) against glutamate‐induced oxidative stress in the mouse hippocampal HT22 cells. DGC significantly reduced cytotoxicity and reactive oxygen species (ROS) generation induced by glutamate in HT22 cells, whereas DGC did not restore glutathione depletion caused by glutamate. In addition, we investigated further whether DGC affected the expression of heme oxygenase (HO)‐1, one of major cellular antioxidant defense system, and found that DGC dose‐dependently increased HO‐1 expression. DGC‐mediated cytoprotection of HT22 neuronal cells from glutamate insult was abrogated by either Tin protophorphyrin (SnPP), an inhibitor of HO‐1, or AKT inhibitor (LY294002). In conclusion, the present results demonstrate for the first time that DGC protects neuronal cells against glutamate‐induced oxidative injury through the induction of HO‐1 expression which is, in turn, activated by PI3k/AKT signaling pathway.
Evidence for K‐Cl cotransporter heterodimerization
Authors: Ponce-Coria Jose , Ding Jinlong , Delpire Eric
Published: June 2021

In humans, mutations in the gene SLC12A6 which encodes for KCC3 result in an autosomal recessive disease, known as ACCPN (Agenesis of the Corpus Callosum associated with Peripheral Neuropathy). In the present work we focused our efforts in understanding the lethality demonstrated by the homozygosity of the Glu289Gly (E289G) mutation in the mouse K‐Cl cotransporter KCC3. This embryonic lethality, which is a much stronger phenotype than the one observed in the KCC3 knockout mouse, seem to indicate dominant negative effects of the mutant cotransporter upon other K‐Cl cotransporters. Using Xenopus laevis oocytes, as a heterologous expression system, we show that KCC2 activity and cell surface expression are significantly reduced when co‐expressing wild‐type or mutant KCC3 proteins. Interestingly, KCC2 activity was not compromised when co‐expressing KCC3 mutations (R207C and T813X) that lead to ACCPN. We also present evidence indicating that the E289G mutation impairs KCC3 glycosylation. Finally, we show that a similar mutation in KCC2 (E201G), also results in the loss of K‐Cl cotransport function through trafficking impairment to the plasma membrane.
Amino Acid Sequence of the Calcium Activated Potassium Channel (BK) In the Skate, Leucoraja Erinacea
Authors: King Benjamin , Clusin William T. , Kao Peter
Published: June 2021

Ca‐activated K channels were first described in the electroreceptor of the skate which has excitable receptor cells. Ca activated BK channels are also present in auditory hair cells, and their AA sequence and structure are known. While most Ca activated K channels respond to both Cai and voltage, the currents in skate electroreceptor are voltage insensitive. Assemblies of transcriptome and draft whole genome sequences from skate embryos were analyzed to find the ortholog of human gene, KCNMA1, that encodes the principal subunit. Ca‐activated K channels consist of 7 membrane spanning regions (S0–S6) and 4 intracellular domains (S7 – S10). Comparison of the 1147 AA skate channel with the mouse BK channel shows high homology, especially in S0 – S10, and in the pore region. There is complete homology of S0 – S3, S5, S6, the pore and S10. The voltage sensor region of S4 and also S7 show one amino acid change. S9 shows 3 changes, and S8 4 changes. The largest variations are in the S8 – S9 linker (which is missing a region of 155 AA's) and in the extracellular region preceding S0, which has only about 50% homology, and also contains a region of 33 AA's not present in mouse or human. Since the extracellular portion of S0 is known to tether the voltage gate, this could explain the apparent lack of voltage gating. The expression and splicing of BK channels in the electroreceptor is under investigation.
Hypoxia induced subunit switching on cytochrome c oxidase in sleep apnoea patients
Authors: Schiffer Tomas , Larsen Filip J , Lundberg Jon , Weitzberg Eddie
Published: June 2021

Obstructive sleep apnoea syndrome (OSAS) is characterized by nocturnal arterial desaturation with sustained hypertension and increased oxidative stress. For unknown reasons, exercise capacity is reduced and resting metabolic rate is increased in OSAS patients. Mitochondrial cytochrome c oxidase (COX) has emerged as a regulator of respiratory control and cell studies indicate that subunits of COX can switch between different isoforms in response to changes in oxygen availability.

Objective

To study intrinsic changes in the nuclear subunit composition and kinetic properties of COX in OSAS patients compared to a control group.

Methods

Skeletal muscle biopsies were taken from tibialis anterior. Subunit composition was quantified by western blotting and intrinsic activity of COX was measured spectrophotometrically in the presence and absence of an ATP‐regenerating system.

Results

Total citrate synthase, COX1 content and COX activity were unchanged in the OSAS patients, indicating unaltered overall mitochondrial biogenesis. In contrast increased expression of COX IV‐2 was found (P<0.05) along with a trend of increased COX IV‐ 1 (P= 0.11). The mitochondrial protease LON responsible for the degradation of COX IV‐1 trended to decrease (P=0.09).

Conlusion

Patients with OSAS exhibit a switch in COX subunits and levels of LON as a result of intermittent nocturnal hypoxia.
Egr1 plays a key role in fetal programming of gender‐dependent PKCε gene expression patterns in the developing heart
Authors: Chen Man , Zhang Lubo
Published: June 2021

Fetal hypoxia resulted in PKCε gene repression in the heart leading to the heightened heart susceptibility to ischemic injury in adult male offspring. The present study examined the role of Egr1 in hypoxia‐mediated PKCε gene repression. Pregnant rats were divided into normoxic and hypoxic (10.5% O2 from day 15 to 21 of gestation) groups. The male and female progeny were studied at 21 day of gestation and 3 months of age. Hypoxia significantly decreased PKCε mRNA and protein abundance in male fetal and offspring hearts. In accordance, CpG methylation of the Egr1 binding site at PKCε promoter was significantly increased in male hearts by hypoxia. Methylation of the Egr1 binding site significantly decreased Egr1 binding to the promoter. In fetal hearts, there was significantly greater abundance of estrogen receptor α (ERα) and β (ERβ) isoforms in females than in males. Both ERα and ERβ interacted more with the Egr1 binding site in the female fetal hearts than in males in both normoxic and hypoxic groups. The results indicate a key role for CpG methylation of Egr1 binding site in hypoxia‐mediated and gender‐dependent PKCε gene repression in the developing heart, and suggest a possible protective role of ER in fetal programming of aberrant gene expression patterns in the heart. (Supported in part by NIH grants HL82779 and HL83966).
Direct Inhibitory Effect of Hypoxia on Cardiomyocyte Proliferation in Fetal Rat Hearts
Authors: Tong Wenni , Xiong Fuxia , Li Yong , Zhang Lubo
Published: June 2021

Maternal hypoxia inhibits cell proliferation in the heart of fetal and neonatal rats. This study determined the direct effect of hypoxia on cardiomyocyte proliferation in fetal rat hearts. Isolated hearts of day 17 fetal rats and rat embryonic ventricular myocyte H9c2 cells were treated ex vivo with 21% or 1% O2 for 48 or 24 h. Bromodeoxyuridine (BrdU) and Ki‐67 were examined by immunohistochemistry (IHC) and immunofluorescence (IF), respectively. The expression of tissue inhibitors of metalloproteinases (TIMP) −3 & −4, cell division marker cyclin D2 and cell division inhibitor p27 was measured by Western blots. IHC staining indicated decreased numbers of BrdU positive nuclei in hypoxic‐treated fetal hearts. Analysis of double IF revealed a predominant distribution of Ki‐67 in cardiomyocytes in fetal hearts, and hypoxia caused a reduction of Ki‐67 colocalization with cardiomytocytes. In accordance, decreased Ki‐67 positive nuclei were demonstrated in H9c2 cells under the hypoxic condition. Cyclin D2 was decreased in hypoxic fetal hearts and H9c2 cells. In contrast, hypoxia enhanced the expression of p27, TIMP‐3 and TIMP‐4 in fetal hearts and H9c2 cells. The results suggest that hypoxia has direct inhibitory effect on cardiomyocyte proliferation in the developing heart, which may be mediated by the upregulation of TIMP‐3 and/or TIMP‐4. (Supported in part by NIH grants HL82779 and HL83966).
Hypoxia affects muscle cell differentiation : the translational repressor 4E‐BP plays a key role
Authors: Hidalgo Magdalena , Le Bouffant Ronan , Bello Valérie , Buisson Nicolas , Cormier Patrick , Darribère Thierry , Beaudry Michèle
Published: June 2021

The availability of oxygen influences cell growth, proliferation, differentiation and survival. The lack of oxygen affects embryonic cells and molecular mechanisms involved are still unknown. We observed that hypoxia rapidly leads to developmental delay and increase of cell apoptosis after a long term hypoxia exposure during Xenopus embryogenesis. Incubating embryos in hypoxia decreased AKT phosphorylation, reversibly increased embryos lethality and protein level of the translational repressor 4E‐BP. Muscle cell differentiation analyses indicated that hypoxia did not alter somitogenesis but affected proliferation and differentiation without modifying the protein level of MyoD and MRF4 transcription factors. Moreover, the accumulation of the non‐phosphorylatable 4E‐BP protein induced muscle differentiation damage similar to hypoxia conditions. These studies suggest that 4E‐BP protein plays a key role in hypoxia, promoting the cap‐independent translation and specific defects in muscle differentiation.
Evidence that activation of both vagal and glossopharyngeal afferents cause the release of 5‐HT in the NTS
Authors: Hosford Patrick Steven , Millar Julian , Ramage Andrew G
Published: June 2021

Pharmacological studies indicate that 5‐HT is released in the nucleus tractus solitarii (NTS) in response to cardiovascular afferent activation. Experiments using a modified form of fast differential voltammetry were carried out to determine if this release of 5‐HT could be detected in the NTS. Rats were anaesthetized with [alpha]‐chloralose (120 mg kg−1; i.v), neuromuscular blocked and artificially ventilated. Activation of cardiopulmonary afferents by phenylbiguanide (PBG; i.a.) caused a transient rise in 5‐HT of 17.8 ± 2.5nM. Citalopram (1 mg kg−1; i.v.) had no effect, while the OCT3/PMAT inhibitor decynium‐22 (600 [micro]g kg−1, i.v.) potentiated this increase in 5‐HT from 18 ± 4 to 70 ± 11 nM. Increasing baroreceptor afferent input with i.v. noradrenaline increased 5‐HT release, while decreasing this input with i.v. sodium nitroprusside had no effect. Citalopram (1 mg kg−1) had no effect on these responses. Activation of the chemoreflex with i.a. sodium cyanide caused a maintained rise in 5‐HT of 27 ± 6 nM. The data supports the view that cardiovascular afferents cause the release of 5‐HT in the NTS.
POMC‐GLP‐2R signaling and action in the control of feeding behavior and gastric motility
Authors: Guan Xinfu , Shi Xuemei , Li Depei , Li Xiaojie , Wang Yi , Chang Benny , Chan Lawrence
Published: June 2021

Glucagon‐like peptides (GLP‐1/2) are released in response to food intake. Central infusion of GLP‐2 suppresses food intake and gastric motility, and this is supposedly mediated through its receptor (GLP‐2R) action in the brain. However, the physiological relevance of GLP‐2R in the brain is unknown. Thus, our aims were to determine if GLP‐2R in POMC neurons regulates feeding behavior and gastric motility. [1] We generated mice with Glp2r deletion in POMC neurons, which showed late‐onset obesity, higher food intake, increased meal frequency, and accelerated gastric emptying using 13C‐octanoic acid breath test. For liquid meal, half‐excretion time was 29.0 ± 4.5 and 51.2 ± 4.5 min; and lag phase 17.8 ± 3.0 and 31.5 ± 3.0 min for the KO and WT mice, respectively. [2] We generated POMC‐specific p110α knockout mice and POMC‐specific FoxO1‐GFP over‐expression mice to define cellular mechanisms underlying GLP‐2‐initiated anorexic action. Using immunoprecipitation, we found that GLP‐2R interacted with p85α in hippocampal neurons. GLP‐2 acutely induced GLP‐2R translocation from membrane to cytoplasm, and enhanced Akt phosphorylation in a PI3K‐dependent manner. Moreover, GLP‐2 (at 20 nM for 30 min) induced nuclear exclusion of FoxO1‐GFP in POMC neurons, and this effect was abolished in POMC‐specific p110α KO mice, suggesting that GLP‐2 may disinhibit expression of FoxO1‐targeted genes in POMC neurons. Furthermore, GLP‐2 differentially modulated excitation of functionally‐segregated POMC neurons in a PI3K‐dependent manner. In conclusion, Glp2r deletion in POMC neurons impairs feeding behavior and gastric motility; and GLP‐2 acutely activates the PI3K signaling pathway in POMC neurons to modulate neuronal excitation and gene expression. Therefore, CNS GLP‐2R plays an important, physiological role in the control of food intake and gastric emptying.
Prolonged TRPV1 activation increases frequency and amplitudes of glutamatergic events in NTS neurons
Authors: Hofmann Mackenzie E , Fawley Jessica A , Andresen Michael C
Published: June 2021

TRPV1 is located presynaptically at some 2nd order neurons in the solitary tract nucleus (NTS) and its activation causes release of glutamate from vesicles independent of action potentials. Here we investigated whether prolonged activation of TRPV1 causes fast receptor desensitization similar to spinal afferents (~30 sec). In patch recordings, capsaicin (100 nM), a TRPV1 agonist, triggered increases in frequency (1385.1 ± 454.6%) and, surprisingly, amplitudes (149.0 ± 18.4%) of spontaneous or miniature EPSCs (n=6). Capsaicin responses rapidly (1 min) peaked with a slow decay of 19.9 ± 3.3 min (n=4) before returning to baseline. To guard against errors from compound events, we reduced release frequency by lowering external calcium from 2 to 1 mM or by reducing capsaicin to 50 nM. Both maneuvers reduced the peak frequencies but capsaicin increased mEPSC amplitudes nonetheless. Finally, increases in temperature activate TRPV1 independent of capsaicin. Increases in temperature resulted in increases to event frequency and amplitudes (184.5 ± 2.0% and 116 ± 2.8%, respectively, n=2). Potentially, presynaptic calcium stores might contribute to the amplitude changes but postsynaptic trafficking of AMPA receptors cannot yet be ruled out. Lastly, TRPV1 desensitization occurs slowly in ST afferents in NTS and TRPV1 might provide uniquely sustained TRPV1 signaling at NTS neurons.
Experimental spinal cord injury alters the dose response of vagal motoneurons to TRH
Authors: Holmes Gregory M , Swartz Emily M
Published: June 2021

Spinal cord injury (SCI) elicits immediate and profound gastric dysmotility. The stomach is modulated by gastric sensory signals transmitted via the vagus nerve to the nucleus tractus solitarius (NTS). The NTS integrates sensory information with signals from throughout the CNS and projects to nuclei which include preganglionic efferent neurons located in the dorsal motor nucleus of the vagus (DMV).

This vago‐vagal reflex remains anatomically intact after SCI and our previous reports suggest that SCI diminishes vagal afferent sensitivity. However, derangements in efferent signals to the stomach may also account for reduced motility. Thyrotropin releasing hormone (TRH) profoundly modulates gastric motility by a direct depolarization of DMV neurons and offers a pharmacological tool to test DMV efferent integrity.

We tested the hypothesis that experimental SCI induces functional impairment of rat DMV motoneurons by microinjecting TRH into the DMV 3 days after SCI or control surgery.

Our data reveal a rightward dose‐response shift to unilateral DMV microinjection of TRH (0, 3, 10, 30 or 100 pmoles, n=40 total). Specifically, gastric motility response to 3pmoles TRH was reduced in SCI animals vs. surgical controls.

Combined with our previous reports, these data suggest that SCI may also impair vagal preganglionic motoneurons. The mechanism leading to this impairment remains to be determined.
A theoretical study of the physiological significance of respiratory sinus arrhythmia
Authors: Ben-Tal Alona , Shamailov Sophie S. , Paton Julian F.R.
Published: June 2021

Respiratory sinus arrhythmia (RSA) is a phenomenon whereby the heart rate increases during inspiration and decreases during expiration. We used mathematical models to test two hypotheses for the physiological function of RSA: 1) a previously suggested hypothesis that RSA improves gas exchange efficiency and 2) a new hypothesis that RSA minimizes the work done by the heart while maintaining physiological levels of arterial carbon dioxide. The study was performed in two parts. First, the optimal heart rate (HR) was calculated using techniques from optimal control theory. Second, the HR function was prescribed and the cardiac work, as well as the volumes of oxygen and carbon dioxide taken up or removed by the blood respectively were calculated. We found that although gas exchange efficiency improved with slow and deep breathing and with increased mean heart rate, this was unrelated to RSA. When we tested the second, new hypothesis by direct calculation of the HR we found that the calculated HR was remarkably similar to RSA and that this became more profound under slow and deep breathing. When the HR was prescribed, we found that cardiac work was minimized for RSA‐like HR functions when the blood partial pressure of carbon dioxide was controlled, most profoundly under slow and deep breathing. These findings provide new insights into potential benefits of RSA under physiological conditions. Supported by NIH grant R01 NS069220.
Ventilatory chemoreflex enhancement in cigarette smokers is reversed by ascorbic acid
Authors: Leuenberger Urs A. , Vazquez Robert , Drew Rachel C. , Muller Matthew D. , Sauder Charity , Blaha Cheryl , Mast Jessica
Published: June 2021

Cigarette smoking causes oxidative stress in humans. Furthermore, in animal models carotid chemoreceptor afferent activity is enhanced by reactive oxygen species and attenuated by antioxidant interventions. To test the hypothesis that chemoreflex control is altered in cigarette smokers and is normalized with an antioxidant, we determined the hemodynamic, ventilatory and sympathetic (peroneal microneurography) responses to transient hypoxia (2–8 breaths of 100% N2), hyperoxia (100% O2, 5 min), and fatiguing static handgrip exercise before and following intravenous infusion of ascorbic acid (60 mg/kg) in cigarette smokers free of overt cardiovascular disease (age 45±4 yrs, body‐mass‐ index 26±2 kg/m2). Compared to a non‐smoking control group (n=11), in smokers the ventilatory responses to transient hypoxia (i.e., the ventilatory chemoreflex slopes) were enhanced (P<0.05, n=11). Importantly, these responses were partly normalized by ascorbic acid (pre vs. post: 0.58±0.08 vs. 0.45±0.06 L/min/% O2 desaturation; P<0.05). In contrast, ascorbic acid did not affect the neurocirculatory responses to hyperoxia (P=NS, n=10) or static handgrip exercise (P=NS, n=7). These data suggest that in cigarette smokers oxidative stress contributes to chemoreflex dysfunction.

Supported by P01 HL077670 and UL1 RR033184.
Intrarenal and sympathetic premotor neuron changes in response to denervation of ischemic kidney in renovascular hypertension
Authors: Nishi Erika Emy , Bergamaschi Cassia T , Gomes Guiomar N , Perry Juliana C , Naffah-Mazzacoratti Maria G , Castro Eduardo F , Campos Ruy R
Published: June 2021

AT1R upregulation in the rostral ventrolateral medulla (RVLM) contributes to sympathoexcitation and arterial hypertension in the 2‐kidney,1‐clip (2K1C) model. Our aim was to investigate whether afferent and efferent renal sympathetic nerves play a role in the modulation of Ang II receptors expression in the central nuclei (RVLM and PVN) and renal lesion markers in renovascular hypertension. Renal denervation of clipped kidneys (DnX: visible bundles were dissected + 10% phenol) was performed in Wistar male rats (n=5/group) 4.5 weeks after clipping. Ten days after DnX the mean arterial pressure was significantly (p<.05) reduced (202 ± 6 vs 178 ± 9 mmHg) in the 2K1C rats. The AT1R was upregulated in the RVLM (73%) and PVN (43%) in the 2K1C group, DnX normalized these expressions in both nuclei. The AT2R expression was increased in the RVLM (76%) and PVN (76%) of 2K1C group and DnX reduced AT2R in both regions. Renal lesion was characterized by cortical interstitium α‐smooth muscle actin (α‐SMA) immunohistochemical expression. The α‐SMA expression was augmented in the clipped (67 fold) and nonclipped (127 fold) kidneys and DnX significantly reduced α‐SMA in both kidneys (9 and 25 fold, respectively) of 2K1C rats. DnX produced no changes in control rats. Thus, our data show that renal nerves may modulate Ang II receptors in the RVLM and PVN and contribute to renal lesion in the renovascular hypertension.

Supported by FAPESP and CNPQ
Local reductions in synaptic inputs to the phrenic motor pool elicits atypical Protein Kinase C (aPKC) and Tumor Necrosis Factor alpha (TNFá) dependent inactivity‐induced phrenic motor facilitation
Authors: Strey Kristi Ann , Baker-Herman Tracy Lee
Published: June 2021

A central neural apnea in ventilated rats elicits an aPKC and TNFα dependent form of plasticity called inactivity‐induced phrenic motor facilitation (iPMF), a rebound increase in phrenic burst amplitude that is apparent when respiratory neural activity is restored. We hypothesized that iPMF following local reductions in synaptic inputs to the phrenic pool occurs via similar mechanisms. Bilateral phrenic output was recorded in anesthetized and ventilated rats. Procaine or vehicle (~200 nl) was injected in the C2 ventrolateral funiculus (VLF) to reversibly reduce axon conduction (~25 min) on one side of the spinal cord. Procaine reduced ipsilateral (−82 + 5 %baseline, p<0.05), but not contralateral (−22 + 16 %baseline, p>0.05) phrenic amplitude. Upon axon conduction recovery, only ipsilateral phrenic amplitude was significantly increased (60 min post: ipsi: 83± 22 %baseline, p<0.01; contra: 33 + 13 %baseline, p>0.05); while no changes in ipsilateral or contralateral phrenic amplitude were observed in vehicle treated rats (10 + 6 and 6 + 8 %baseline; p>0.05). Intrathecal aPKC inhibitor (ZIP) or TNFα scavenger (sTNFR1) blocked ipsilateral iPMF (60min: 24 + 11 and 16 + 7 %baseline, respectively, p>0.05). These data suggest that iPMF induced by local reductions in descending synaptic inputs to the phrenic pool require similar cellular pathways as iPMF following global reductions in respiratory neural activity. NIH HL105511
Characterization of the relationship between inspiratory neural discharges and the micturition reflex in decerebrate and urethane‐anesthetized adult in vivo rat
Authors: Shen Tabitha , Collins William F. , Solomon Irene C.
Published: June 2021

Previous studies have characterized respiratory neural outputs during the micturition reflex (MR). However, these studies primarily were conducted in cats, and it is not known if the relationship seen in the cat model is maintained in rodent models. To begin to address this issue, we recorded bladder pressure and phrenic (Phr), hypoglossal (XII) and pudendal motor nerve activity in decerebrate or urethane‐anesthetized vagi‐intact adult rats during passive bladder filling and active bladder contraction. Spontaneous MRs were elicited by slow infusion of saline into the bladder. The data show increased Phr post‐inspiratory activity and a transient increase followed by a transient decrease in burst frequency (due to changes in TE). Small XII neural discharges were observed during expiration while the bladder actively contracted. In contrast to cat data, no changes in Phr or XII amplitude were observed. Finally, while severe hypercapnia and hypocapnia affected respiratory patterns, they did not affect the MR. We conclude that, while there are some similarities to the cat model, a different relationship between respiration and micturition occurs in rat. Supported by HL63175
Inhibition of brain endoplasmic reticulum (ER) stress attenuates hypertension in diet‐induced obesity (DIO)
Authors: Mark Allyn L , Young Colin N , Butler Scott D , Guruju Mallikarjuna , Davisson Robin L
Published: June 2021

ER stress in brain metabolic centers has been implicated in the pathogenesis of obesity‐hypertension, independent of effects on metabolic pathways. We recently reported molecular and ultrastructural evidence for DIO‐mediated activation of ER stress in key brain cardiovascular control regions. We tested the hypothesis that inhibition of brain ER stress with the chemical ER chaperone TUDCA attenuates obesity‐hypertension. Adult male C57Bl/6 mice were fed a high fat (HFD, n=8) or control (CON, n=6) diet for 21 wks. Mice were then implanted with radiotelemeters and intracerebroventricular (ICV) cannulae and allowed 1 wk recovery. DIO mice had elevated MAP (121±1 vs 112±1 mmHg; P<0.05) and white adipose tissue (1.67±0.01 vs 0.59±0.09 g; P<0.05) and liver weights (1.77±0.18 vs 1.27±0.04 g; P<0.05) compared to CON. ICV TUDCA (5 μg/day, 3 days) decreased MAP in DIO mice compared to ICV vehicle (115±2 vs 120±1 mmHg; P<0.05), whereas it had no effect on MAP in CON mice (TUDCA, 113±3 vs Vehicle, 114±1 mmHg; P>0.05). ICV TUDCA also decreased body (−5.1±1.2 g vs 0.1±1.0 g; P<0.05) and liver weights (1.19±0.08 vs 1.77±0.18g; P<0.05) compared to vehicle, but had no effect on white adipose tissue mass (1.71±0.29 vs 1.67±0.01 g; P>0.05). These data suggest that inhibition of brain ER stress attenuates hypertension and hepatic enlargement but not white adipose tissue mass in DIO mice.

HL063887, HL084207
Positive correlation between cyber leisure time and sympathetic activity in high school students
Authors: Son Mi Eun , Kim Na-Hyun , Kong In Deok
Published: June 2021

Purpose

The purpose of this research was to find out the relationship between cyber leisure time and autonomic nerve system in high school students.

Methods

The subjects of this study were 262 second graders at high school located in D city. The research design was descriptive correlation study. Data were collected from August 26 to September 17, 2010, using cyber leisure questionnaire and heart rate variability by SA‐6000 for autonomic balance.

Results

Total time for the cyber leisure was 385.8±261.7 (min/week). Time for internet search and computer game was 230.0±139.7 (min/week) and 155.8±163.1 (min/week), respectively. There were significant positive correlation between cyber leisure time and sympathetic activities (r=.13, p<.05).

Conclusion

The use of the internet and computer game could potentiate sympathetic activities in high school students. Thus, nursing intervention to reduce the total cyber leisure time will be helpful to improve physical, physiological, and psychosocial health for them.
Integrative responses of neurons in nucleus tractus solitarius to stimulation of visceral and vestibular afferents
Authors: Sugiyama Yoichiro , Suzuki Takeshi , Destefino Vincent J , Yates Bill J
Published: June 2021

Although the vestibular nuclei project to nucleus tractus solitarius (NTS), little is known about the effects of vestibular inputs on NTS neuronal activity. Lesions of NTS abolish vomiting elicited by a variety of triggering mechanisms, including vestibular inputs. Thus, an emetic stimulus that activates gastrointestinal (GI) receptors could alter the responses of NTS neurons to vestibular inputs. We examined in decerebrate cats the responses of NTS neurons to rotations of the body before and after the intragastric administration of the emetic compound CuSO4. The activity of > 30% NTS neurons was modulated by vestibular stimulation, with most of the responsive cells having their firing rate altered by rotations in the head‐up or head‐down directions. These responses were aligned with head position in space, as opposed to the velocity of head movements. The activity of NTS neurons with baroreceptor, pulmonary and GI inputs could be modulated by vertical plane rotations. However, injection of CuSO4 into the stomach did not alter the responses to vestibular stimulation of NTS neurons that received GI inputs, suggesting that the stimuli did not have additive effects. These findings show that the detection and processing of visceral inputs by NTS neurons can be altered in accordance with the direction of ongoing movements.