bluuebunny/crossref_metadata_2025 huggingface dataset:
Oscillating wildly: Turning the evolution of respiratory rhythm generation on its head
Authors: Baghdadwala Mufaddal , Trask William , Wilson Richard
Published: June 2021

How the neuronal control of air breathing evolved is unknown. Brainstem circuits controlling breathing have only been investigated in a small handful of extant vertebrates. This makes an evolutionary analysis challenging.

In the frog, we have found evidence for three areas involved in respiratory rhythm generation, each with distinct pharmacologies: the buccal area in rhombomere 7 as well as both lung burst priming and lung burst power stroke regions situated in rhombomeres 4‐5. We have long assumed that circuits generating air breathing in mammals and frogs are homologous, evolving from a common ancestry. However, there are some inconsistencies with this assumption. The primary inspiratory oscillator in mammals, the PreBötzinger Complex (PreBötC), is located in rhombomere 7‐‐the same rhombomere as the frog buccal area‐‐and the rhythms produced by buccal and PreBötC are stubbornly independent of CO2. In comparison, like pre‐inspiratory/expiratory activity in mammals, the lung bursts in the frog are highly CO2 sensitive, and both originate in rhombomere 4‐5.

These data suggest that we may have to turn our previous hypothesis that the frog lung area and PreBötC are homologous on its head and consider the possibility that the mammalian PreBötC evolved from a fish oscillator used for water‐breathing. Until more studies on non‐mammalian vertebrates are performed any hypothesis on the evolution of air breathing is but a work in progress, and with so little data currently available, further oscillations are likely.

This work was funded by NSERC.
Cardiomyocyte Specific Bmal1 Deletion Triggers Extracellular Matrix Response Associated with Markers of Impaired Inflammation Resolution and Diastolic Dysfunction
Authors: Ingle Kevin , Kain Vasundhara , Goel Mehak , Prabhu Sumanth , Young Martin , Halade Ganesh
Published: June 2021

The mammalian circadian clock consists of multiple transcriptional regulators that coordinate biological processes in a time‐of‐day‐dependent manner. Cardiomyocyte‐specific deletion of the circadian clock component BMAL1 (aryl hydrocarbon receptor nuclear translocator‐like protein 1) leads to age‐dependent dilated cardiomyopathy and decreased lifespan in mice. We investigated whether cardiomyocyte‐specific BMAL1 knockout (CBK) mice display early alterations in extracellular matrix (ECM) remodeling, inflammation modulators, and cardiac diastolic function. By 28 weeks of age, CBK mice developed diastolic dysfunction, ventricular hypertrophy, increased fibrosis and expression of ECM‐regulatory genes, as well as a gene expression pattern consistent with impaired resolution of inflammation (compared to aged matched controls). More specifically, CBK mice exhibited (p<0.05): 1) increased fibrosis in the interstitial and endocardial regions; 2) increased (>1.5 fold) expression of collagen I and III, as well as the matrix metalloproteinases MMP‐9, MMP‐13, MMP‐14; 3) increased transcript levels of neutrophil chemotaxis and leukocyte migrationgenes (Ccl2, Cxcl2, Cxcl1, Cxcr2); and 4) decreased levels of 5‐LOX, HO‐1 and COX‐2, enzymes that promote the resolution of inflammation. In conclusion, genetic disruption of the cardiomyocyte circadian clock results in ECM remodeling, pro‐inflammatory gene expression profiles, and diastolic dysfunction.
Identification of Mitochondrial Proteins Involved in Acute Estrogen‐Induced Cardioprotection Via GPER1
Authors: Lan YongSheng , Olde Bjorn , Leeb‐lundberg Fredrick , Bopassa Jean C.
Published: June 2021

We recently found that activation of G‐protein coupled estrogen receptor (GPER1) with G1, its agonist, induces cardioprotective effect against ischemia/reperfusion injury by the inhibition of the mitochondrial permeability transition pore. Here, we identified regulated mitochondrial proteins involved in estrogen action after ischemia/reperfusion. Isolated hearts from male WT (C57BL/6NCrL) or GPER1‐KO mice hearts were perfused using the Langendorff technique with Krebs Henseleit buffer (control) or with the addition of estrogen (40nM). Hearts were subjected to 18min ischemia followed by 10min reperfusion. Mitochondria were isolated and 2D‐DIGE followed by mass spectrometry was performed. Proteins of interest were the ones (up‐ or down‐ regulated) in WT+E2 vs. WT‐control that remained unchanged in GPER1‐KO+estrogen vs. GPER1‐KO‐control and WT‐control vs. GPER1‐KO‐control. Robust changes of proteins were observed in 45 spots, out of which 14 were downregulated and 31 upregulated. In these spots, 52 unique proteins were identified. Estrogen treatment down‐regulated filament proteins (filamin A,B,C) and the mitofilin, which controls mitochondrial cristae morphology, upregulated activating transcription proteins, and contractile proteins (tropomyosin and myosin), and regulated proteins acting in stress (stress‐70 protein, and 60 kDa heat shock protein), in cell communication (glial fibrillary acidic protein), in electron transfer chain and ATP production, and in signaling pathways (membrane‐associated phosphatidylinositol transfer protein). In conclusion, acute estrogen effects via GPER1 activation are associated with the down‐ or up‐regulation of mitochondrial and non‐mitochondrial proteins likely in close contact to mitochondria.
The Effect of Succinate on Skeletal Muscle Respiration in Diet Induced Obesity and Insulin Resistance
Authors: Slocum Cheyanne , Escudero Daniela , Sheridan Caitlin , Legesse Saada , Lagalwar Sarita , Reynolds Thomas , Ives Stephen
Published: June 2021

Obesity and insulin resistance are associated with mitochondrial dysfunction. We sought to determine the effect of succinate, an electron donor at complex II of the mitochondria, on insulin action, energy homeostasis, and muscle mitochondrial function. C57B6 male mice were randomly assigned to a low fat diet (LFD) or a high fat diet (HFD) for 20 weeks. After 14 weeks of the dietary intervention, mice from within a diet group were assigned to a control or succinate (0.75 mg/ml in drinking water) group. Caloric intake, water consumption, and body mass were assessed weekly, while glucose tolerance (GT), insulin tolerance (IT), energy expenditure (EE), and spontaneous physical activity (PA) were assessed during the last 2 weeks of succinate treatment. In vitro measurements of mitochondrial function in soleus muscle were performed using permeabilized fiber respirometry. As expected, the HFD increased body mass, epididymal white adipose tissue (EWAT) mass, and reduced GT and IT. However, succinate treatment had no effect on any in vivo measurements (body mass, EWAT mass, GT, IT, EE, or PA). Despite impaired insulin action, there was no effect of diet on soleus muscle mitochondrial respiration, however, a trend to increase complex I+II driven state 3 respiration, and complex IV activity was evident in mice that received succinate. In conclusion, we observed no effect of succinate treatment on insulin action, energy homeostasis, or physical activity. In oxidative skeletal muscle, there was a tendency for increased state 3 respiration, owed to greater mitochondrial content, suggestive of a succinate‐induced mitochondrial biogenesis.
Circulating Branched Chain Amino Acids are Associated with Body Composition and Physical Function in Older Adults
Authors: Lustgarten Michael , Fielding Roger
Published: June 2021

Identification of mechanisms underlying age‐related alterations in body composition and decreases in physical function will be important for addressing the growing challenge of providing health care to the rapidly expanding aging population. The goal of the current study was to use mass spectrometry‐based metabolic profiling in combination with principal components analysis (PCA) and multivariable‐adjusted linear regression to provide insight into biologic mechanisms that may underlie body composition and physical function in older adults (N=73). Branched chain amino acids (BCAA: leucine, isoleucine, valine) or their related degradation products were negatively associated with total fat mass, positively associated with thigh muscle cross sectional area (CSA) and the fat‐free mass index (total lean mass/height2), but were both positively and negatively associated with mobility (400 meter gait speed; 400‐m). Collectively these data suggest a role for BCAA metabolism in mechanisms related to body composition and physical function in older adults. Future studies aimed at validation of these results in a larger cohort, and, that test the causative role of these associations are of interest.

Component Loadings
β ± SE
p‐value

Total Fat

AA Factor 5: Valine, Leucine, Isoleucine
0.80, 0.77, 0.76
‐1.5 ± 0.4
0.001

Muscle CSA

AA Factor 2: 4‐methyl‐2‐oxopentanoate, 3‐methyl‐2‐oxovalerate, 3‐methyl‐2‐oxobutyrate
0.87, 0.83, 0.83
6.2 ± 2.0
0.003

AA Factor 5: Valine, Leucine, Isoleucine
0.80, 0.77, 0.76
6.9 ± 1.9
0.0004

FFMI

AA Factor 5: Valine, Leucine, Isoleucine
0.80, 0.77, 0.76
0.6 ± 0.2
0.0002

400‐m

AA Factor 4: α‐hydroxyisovalerate, 2‐hydroxy‐3‐methylvalerate, α‐hydroxyisocaproate
0.87, 0.78, 0.78
0.1 ± 0.0
0.02

AA Factor 5: Valine, Leucine, Isoleucine
0.80, 0.77, 0.76
‐0.0 ± 0.0
0.04
Cardiosomes and Cardiac Remodeling: Role of Exercise
Authors: Chaturvedi Pankaj , Kalani Anuradha , Tyagi Suresh
Published: June 2021

Recent findings that exosomes are released from myocytes have pumped up the role of exosomes in cardiac remodeling. Our electron microscopy findings show the release of exosomes from endothelial cells of heart vessels by budding and presence of exosomes in the close vicinity of myocytes and in the extracellular spaces. These exosomes can be termed as ‘cardiosomes’. Although exercise reduces cardiovascular risks including diabetes, the impact of exercise on cardiosomes and consequently cardiac remodeling is unclear. We hypothesize that exosomes released during exercise in diabetes, contain paracrine factors including microRNAs (122a, 455, 29b, 323‐5p and 466) that can bind to the remodeling genes MMPs and TIMPs and affect their expression and hence prevent adverse remodeling in diabetics. To test this hypothesis, we are using 1) db/db mice 1) db/+ mice as controls with and without exercise and investigating the content and amount of exosome release from the heart. The heart function in diabetic mice was assessed by echocardiograph and remodeling was assessed by collagen/elastin ratio and MMP/TIMP ratio. MicroRNAs were assessed by qPCR. Our data suggested that there is exquisite release of exosomes in the diabetic heart with exercise as compared to non‐exercise. The exosomes when evaluated contained high levels of mir29b and 455 which can bind to the 3′ region of MMP9 to bring down its expression and alleviate cardiac remodeling. This is a novel study which suggests that exercise releases exosomes that contain microRNAs which affect the remodeling genes in the heart and hence prevent adverse effects in diabetes.
Effect of chronic dietary quercetin enrichment on cardiac function in dystrophic mice
Authors: Ballmann Christopher , Beyers Ronald , Denney Thomas , Selsby Joshua , Quindry John
Published: June 2021

In Duchenne muscular dystrophy (DMD), cardiac function declines with age and causes 40% of related deaths. New treatments are needed to treat cardiac pathologies related to DMD and preserve cardiac performance across the lifespan. Relative to DMD pathology, consumption of quercetin promotes anti‐inflammatory effects, activates PGC‐1α, up‐regulates endogenous antioxidants, and mitochondrial biogenesis. We investigated chronic 0.2% quercetin dietary enrichment as a strategy to attenuate cardiac function abnormalities in mdx mice. Mdx mice were randomly assigned to: 0.2% quercetin enriched (mdxQ) or control (mdx) diet for 12 months and compared to age matched, control fed C57 mice (n=8/group). Hearts received 7T MRI to quantify cardiac function at 2, 10, and 14 months of age. Reflective of aging, end diastolic volume increased at 14 months in all groups (p=0.001). Quercetin enrichment preserved calculated ejection fraction (p<0.001), stroke volume (p<0.001), fractional shortening (p=0.0013), systolic wall thickness (p=0.006) and cardiac output (p<0.001) at 10 and 14 months in mdxQ compared to mdx. Furthermore, quercetin attenuated increases in end systolic volume at 14 months (p<0.001) in mdx mice. Results confirm age‐dependent declines in cardiac function occur in mdx mice. Data also indicate that chronic quercetin enrichment prevented cardiac dysfunction in mdx mice. Additional experiments are needed to identify physiological mechanisms responsible for protection due to quercetin intake and optimize dosing strategies. Funded by: Duchenne Alliance
Long‐term Dietary Quercetin Enrichment Improves Muscle Function in Dystrophic Skeletal Muscle
Authors: Selsby Joshua , Ballmann Christopher , Quindry John
Published: June 2021

Duchenne muscular dystrophy (DMD) is a fatal muscle wasting disease characterized by progressive muscle injury culminating in loss of ambulation and death. It is now clear that increased muscle PGC‐1α pathway activity improves many aspects of disease pathology. Translating this work to human patients necessitates identification of a safe PGC‐1α activator. The purpose of this investigation was to determine the extent to which dietary enrichment of quercetin, a known PGC‐1α activator, improved skeletal muscle function in mdx mice, a model of DMD. mdx mice were maintained on a control or 0.2% quercetin‐enriched diet from two to 14 months of age before sacrifice and tissue collection. Healthy, C57 mice were maintained on a control diet. At 14 months of age body weight was decreased by 12% (p<0.05) in mdx and by 20% in mdxQ (p<0.05 v C57 and mdx) compared to C57. Soleus muscle mass was increased by 35 and 30% (p<0.05) in mdx and mdxQ, respectively, compared to C57. Tetanic force was similar between all groups. Importantly, dietary quercetin enrichment decreased the 42% reduction in specific tension in the mdx soleus compared to C57 by half (p<0.05). In soleus muscle from mdx mice the force produced during the final contraction of a 10 minute fatigue protocol was 8% of the initial force while that of C57 was 16% (p<0.05). Force produced by mdxQ was 12% of initial force though was similar to both groups. In total, these data clearly indicate that long‐term dietary quercetin enrichment provides a benefit to soleus muscle function and should be considered as part of a therapeutic regimen for DMD patients. Supported by the Duchenne Alliance.
Ras‐Induced Macropinocytosis: Metabolic adaptation to signaling in the absence of adequate nutrients
Authors: Thompson Craig
Published: June 2021

Under conditions of an abundant supply of extracellular glucose and glutamine, cancer cells synthesize lipids, nucleic acids, and non‐essential amino acids from these precursors. However, when cancer grows to exceed its vascular supply, cells must adapt to lower availability of essential nutrients and oxygen. In the past year, we have seen a major breakthrough in the discovery of novel mechanisms by which cancer cells adapt to metabolic stress. It was previously determined that glutamine‐dependent lipid synthesis could support de novo lipid synthesis under hypoxia but metabolic tracing studies uncovered that over 50% of lipids used in phospholipid biosynthesis in hypoxic cells come from exogenous sources. We were able to determine that hypoxia‐induced macropinocytosis facilitates the uptake and incorporation of unsaturated phospholipids to maintain effective unsaturated lipid levels under conditions in which stearoyl‐CoA desaturase is inhibited by oxygen limitation. Follow up studies have demonstrated that this property of cellular scavenging of extracellular macromolecules is induced in a Ras‐dependent fashion in transformed cells and provides a potent mechanism by which Ras‐transformed cells can adapt to metabolic stress in their environment. This pathway of cellular acquisition of bioenergetic substrates has previously escaped detection because, in complete medium, the utilization of macropinocytosed proteins as metabolic substrates is actively suppressed. The molecular details of this suppression and the implication of these studies to understanding both cancer and wound repair will be discussed.
PET Radiopharmaceuticals for the Diagnosis of Cancer
Authors: Lewis Jason
Published: June 2021

The use of Positron Emission Tomography (PET) for cancer imaging is a well‐established and widely used molecular imaging modality both in clinical and research settings. PET offers the ability to quantitatively measure biological and receptor‐based processes using a wide spectrum of specifically designed radiopharmaceuticals exploiting small molecule‐, peptide‐, antibody‐ and nanoparticle‐based platforms.
One novel avenue of application is the PET and molecular imaging of serum biomarkers. One prominent shortcoming in oncology is a high frequency of false positive indications for malignant disease in upfront diagnosis. Because one common cause of false positivism is biomarker production from benign disorders in unrelated host tissues, we hypothesized that probing the site(s) of biomarker secretion with an imaging tool could be a broadly useful strategy to deconvolute the meaning of foreboding but inconclusive circulating biomarker levels. Recent approaches with antibody‐based platforms to image biomarkers will be discussed.
Temperature Effects on the Chick Embryonic Heart Function
Authors: Vostarek Frantisek , Svatunkova Jarmila , Sedmera David
Published: June 2021

The function of the embryonic heart is strongly affected by temperature. Changes in the kinetics of ion channels are crucial for generation and propagation of electricity. We set to analyze in detail the effects of temperature changes on electrical activity of the embryonic chick heart using in vitro high‐speed calcium imaging and in ovo video microscopy.

In embryonic day 4 hearts we found that a decrease in temperature from 37 °C to 34 °C lead in vitro to a 22 % drop of the intrinsic heart rate and unchanged amplitude of Ca2+ transients, compared to a 25% deceleration between 37 °C and 34 °C in ovo. Increase in temperature from 37 °C to 40 °C lead in vivo to 23% and in ovo to 20 % acceleration of the intrinsic heart rate, and a significant decrease in amplitude of Ca2+ transients (atrium ‐35%, ventricle ‐38%). Hyperthermia in vitro increased the incidence of complete atrioventricular (AV) blocks, while no complete AV block was observed in hypothermia. Similar situation was recorded in ovo. Electrical stimulation experiments in ovo suggested that the AV blocks were caused by hypoxia a not by the tachycardia per se. Activation maps placed the location of the AV block at the inner curvature and the AV canal‐ventricular boundary along the outer curvature.

Temperature is thus an important epigenetic factor influencing the function of the developing cardiac conduction system. Increased temperature augments the metabolic requirements of the myocardium, resulting in a relative hypoxia and AV conduction disturbances.

Supported by GACR P302/11/1308 (DS) and GAUK 716214 (FV).
Does Serca2a Mediate the Alcohol Effects on the Heart
Authors: AlRubaiee Mustafa , Dayton Bryan , Jeffress Miara , Umoh Nsini , Haddad Georges
Published: June 2021

Chronic low alcohol exposure has been proven to have beneficial cardiac effects; whereas chronic high alcohol consumption could lead to heart failure. Oxidative stress is thought to be partly responsible for the alcoholic negative effects on the heart function. We have previously shown that cardiac inotropy is closely related to the activation of the survival PI3K/Akt. The objective of this study was to elucidate the signaling pathways conveying the beneficial versus the detrimental effects of chronic low and high alcohol on the heart function, respectively. Littermate adult rats were put on a 4‐months isocaloric Lieber‐Decarli liquid diet with either low alcohol (LA: 5mM) or high alcohol (HA: 100mM) levels. The measured final blood alcohol concentrations were 0.02% and 0.20% respectively. In vivo intra‐ventricular catheterization (Scisense/iWorks) of the left ventricle (LV) showed that an improved LV contractility and ejection fraction of the LA group while the opposite occurred with the HA group. in vitro cellular and sarcomeric inotropic measurements (Ionoptix) showed similar profile to the LV in vivo data. In addition, LA enhanced Ca2+ sequestration in the sarcoplasmic reticulum whereas HA reduced it with elevation of intracellular Ca2+ level.  Our data show that improved cardiac function by LA is mediated by enhanced SERCA2 activity whereas the detrimental effects of HA are associated with reduced SERCA2a function.  Funded by NIH/NIAAA 1 R15 AA019816‐01A1 and 2G12 RR003048 NIH/RCMI, DRI.
CAPILLARY‐TISSUE EXCHANGE OF SUBSTRATES AND NUCLEOSIDES IN CARDIAC ENERGETICS MODELING
Authors: Bassingthwaighte James , Jardine Bartholomew , Raymond Gary
Published: June 2021

Modeling cardiac energetics involves all of the elements of supply or demand. It is complicated: the exchange processes are distributed in space, heterogeneous, requiring parallel units interacting with each other. Multicomponent, multiscale models for the analysis of data are complicated. Using modular units aids building and maintenance. A convenient module is one in which the number of connecting variables is minimized, and the internal complexity is isolated. The differential equation modeling platform JSim is designed for model‐based analysis of data using behavioral and sensitivity analysis, automated data fitting, and MonteCarlo for uncertainty quantification. For O2, CO2, substrates, and metabolites we constructed first a multisolute single capillary‐tissue unit with RBC, plasma, endothelial cells, interstitial space, and cardiomyocytes, ignoring other cell types. The substrates were O2, glucose, and palmitate; the processes were uptake, binding and buffering, and metabolism. Oxygen, binding to hemoglobin, has capillary gradients influenced by CO2, pH, ºC and 2,3‐DPG, requiring partial differential equations. Myoglobin facilitates cytosolic diffusion and buffering. For glucose, there is glycolysis, the pentose shunt, and buffering as glycogen. For palmitate, storage buffering as acyl‐CoA and di‐ and tri‐glyceride feed into beta‐oxidation and the Krebs cycle. Oxidative phosphorylation produces ATP used in muscle filament activation, ion pumps, and cell maintenance. Version 1 uses first order reactions. Mechanistic kinetics with thermodynamic constraints come with substituting high fidelity modules. (NIH grants R01‐EB8407; P50‐GM 094503)
Non‐Genomic ERK1/2 Activation and Integrin αvβ3 Contribute to Cardiac Hypertrophy Induced by Thyroid Hormone
Authors: Lino Caroline , Diniz Gabriela , Moreno Camila , Barreto‐Chaves Maria Luiza
Published: June 2021

Integrin αvβ3 is a transmembrane heterodimer that intermediates extracellular matrix and cytoskeleton signals. Recent studies demonstrate that it may act as a cell surface receptor for thyroid hormones (THs) triggering intracellular signal pathways. In the present study we evaluated the role of integrin αvβ3 on activation of extracellular signal‐regulated kinase (ERK) in promoting cardiac hypertrophy induced by THs. Cardiomyocytes primary cultures were obtained from neonatal Wistar hearts and treated with T3 (triiodothyronine, 15ηM). The cells were pre‐treated with Tetrac (10µM) and PD98059 (20µM), inhibitors of integrin and ERK, respectively. The data were analyzed by One‐way ANOVA followed by Tukey's post hoc test and p>0.05 were considered statiscally significant. ERK phosphorylation is rapidly increased by T3 stimulation, presenting a maximum activation at 5 mins. However, p‐ERK tended to decrease after 30 mins, indicating a transient activation of this signaling. As evidenced by qPCR assays, PD and Tetrac attenuate the increase on alpha‐actin and ANF mRNA levels promoted by T3. Similar results were also observed for [3H]‐leucine incorporation (5µCi/ml) and cell surface area analysis. The involvement of integrin αvβ3 on ERK activation is still in progress. In conclusion, this work suggests the involvement of ERK and integrin αvβ3 in TH‐induced cardiac hypertrophy. This work was supported by FAPESP (2013/16142‐9).
Akita (Type I Diabetic) Mice Develop Bladder Dysfunction
Authors: Kim Alexandra , Hill Warren , Zeidel Mark
Published: June 2021

Although lower urinary tract symptoms (LUTS) occur commonly in diabetics, the symptoms vary widely and the mechanisms involved are poorly understood. We used male Akita mice, a strain which harbors a spontaneous mutation resulting in insulin misfolding and the depletion of β‐cells (C57BL/6‐Ins2Akita/J), to develop a model of LUTS in Type I diabetics (T1D). These mice developed hyperglycemia, which was partially treated with subcutaneous insulin pellets, mimicking poorly controlled T1D in humans. As the animals aged, we performed spontaneous void spot assays and cystometrograms to evaluate urine storage and micturition. At 1 month of age, little difference was observed in the bladder function of the Akitas and the age‐ and sex‐ matched controls. However, by 7 months, Akita mice demonstrated an increase in the total voided volume (P>.05) consistent with diabetic polyuria. By 10 months, void spot assays revealed that spot numbers were significantly elevated (P<0.005), suggesting loss of normal continence, and total voided volumes were larger (506±154 vs 151±63 µl; P<0.005). Cystometry with continuous filling demonstrated multiple pre‐voiding contractions with urine leakage, suggesting overactive bladder and urge incontinence, and longer voiding intervals in Akita mice (905±509 vs 360±160s) consistent with bladder enlargement (P<0.005). Results to date indicate that Akita mice, but not controls develop bladder hypercontractility, myogenic and neurogenic alterations, and compensatory bladder hypertrophy in the initial phase of diabetic disease. Planned measurements at 13 and 16 months will determine the progression of bladder dysfunction in this model of T1D. This model will permit direct investigation of mechanisms underlying bladder dysfunction in diabetes. (Supported by P20 DK097818‐02S2).
Effects of Caffeine and Caffeine‐containing Kolanut (Cola nitida seed) on Glucose Tolerance of the Rat
Authors: Alada Akinola , Afolabi Oladele
Published: June 2021

This study examined the effects of caffeine and kolanut on the glucose tolerance of the rat. Male Wistar albino rats (250 ‐300g) and divided into four groups with 8 rats per group were orally administered ethanolic extract of kolanut (EEK) (6mg/kg), decaffeinated extract of kolanut (DEK) (6mg/kg), caffeine (CAF) (6mg/kg) and distilled water (control) respectively for eight weeks. At 8 weeks, oral glucose tolerance test was carried out on the rats. Plasma glucose concentrations were plotted as a function of time and the areas under the glucose curve (AUGs) calculated. Blood samples and liver biopsies were taken to determine serum insulin levels, liver glycogen, Liver glycogen synthase and phosphorylase activities. Blood glucose was determined by glucose oxidase method. Glycogen level was determined by anthrone method. Radioimmunoassay kit (Diagnostic product) was used to determine serum insulin level. Values are means ± S.E.M, compared by ANOVA and Student t‐test. AUGs increased by 35% and 28% for rats treated with CAF and EEK respectively compared with the control. AUG for for rats treated with DEK was 31% lower than the control. Peak serum insulin levels also increased from 15.1± 0.22µg/ml to 20.65± 0.31 and 20.48± 0.42µg/ml for CAF and EEK respectively and decreased to10.89± 0.01µg/ml for DEK. There was no significant change in the liver glycogen and glycogen synthase activity in all the groups except in CAF group which are 40% and 25% respectively higher than the control. There was no significant difference in the liver phosporylase activity in all the groups. The results showed that caffeine and kolanut extract reduced glucose tolerance most possibly by reducing insulin sensitivity.
The mitochondria‐targeted antioxidant improves age‐related cardiac damage
Authors: Owada Takashi , Saitoh Shu‐ichi , Yamauchi Hiroyuki , Takeishi Yasuchika
Published: June 2021

Senescence is a major factor to increase oxidant stressin mitochondria, which contributes to the pathogenesis of heart diseases. However, the effect of antioxidant therapy on cardiac mitochondria in aging related‐cardiac dysfunctionremains elusive. We postulated that scavenging superoxide targeted in mitochondriawould have benefit in the aged heart. Increased levels of superoxide and NADPH oxidase activity were appeared in old mice (62W) compared to those in young mice (8W) (Superoxide: 2.6±0.4 vs. 1.2±0.2 nmol/mg protein; NADPH oxidase activity: 2654±282 vs. 1124±156 RLU, P<0.01, n=12, respectively). In old mice treated with mitochondria‐targeted antioxidant MitoTEMPO coinfusion using minipump(180 µg/kg/day, 28 days), levels of superoxide and NADPH oxidase activity decreased (0.2±0.2 nmol/mg protein and 342±45 RLU, P<0.01). Echocardiography showed that treatment with MitoTEMPO in old mice improvedleft ventricular ejection fraction (from 48±5% to 62±5%, P<0.01) and diastolic dysfunction of theleft ventricle. Endothelium‐dependent vasodilation in isolated coronary arterioles and oxygen consumption rate in complex I and III of cardiac mitochondriawereimpaired in old mice compared to thosein young mice, which wereimprovedby MitoTEMPO treatment. Resolution of mitochondrial oxidantstress by MitoTEMPO in old mice restored cardiac function and coronary vasodilative capacity to the same magnitude observed in young mice. Therefore, antioxidant strategy targeting mitochondria could have therapeutic benefit in heart diseases with senescence.
ROS Generation Is Involved in Titanium Dioxide Nanoparticle Induced MAPKs/AP‐1 Activation in JB6 Cells
Authors: Ding Min , Bowman Linda , Leonard Stephen , Settle Tabatha , Zaho Jinshun
Published: June 2021

Titanium dioxide (TiO2) is a white mineral used in the manufacturing of paint, paper, plastics, sun tan lotion, and other products. Recent studies indicated that TiO2 nanoparticles cause chronic inflammation and lung tumor formation in rats. It is believed that the toxicity and carcinogenesis of TiO2 is associated with particle size. Since activator protein‐1 (AP‐1) is known to play an important role in the induction of neoplastic transformation and regulation of multiple genes involved in cell proliferation and inflammation, we investigate the potency of TiO2 nanoparticles on reactive oxygen species (ROS) generation and AP‐1 signaling in a mouse epithermal cell line, JB6 cells. Incubation of JB6 cells with TiO2 nanoparticles resulted in a dose dependent generation of •OH radicals. TiO2 nanoparticles caused a 3‐fold increase in AP‐1 activity in the cells. The induction of AP‐1 activity in cultured cells was dose‐dependent. The signal transduction pathways for AP‐1 activation were also investigated and the results demonstrate that TiO2 stimulates mitogen‐activated protein kinase (MAPK) family members, including extracellular signal‐regulated protein kinases(ERKs), p38 kinase, and C‐Jun N‐terminal kinase (JNKs). Inhibition of ERKs, p38 kinase, but not JNKs with specific inhibitors SB203580, PD98059, and SP 600125, inhibited TiO2 nanoparticles‐induced AP‐1 activation, respectively. Thesefindings demonstrate that TiO2 nanoparticles stimulated the generation of •OH radical and induces AP‐1 activation, which may be mediated throughp38 kinase and ERKs pathways.
Compound H Increases Anti‐aging Protein Klotho Expression and Attenuates Arterial Stiffening and Hypertension
Authors: Chen Kai , Chen Jianglei , Sun Zhongjie
Published: June 2021

Background & Objective

The prevalence of arterial stiffness and hypertension increases with age while the klotho level decreases with age. Compound H stimulates klotho mRNA and protein expression in cell cultures and mouse kidneys. The objective of this study is to asses if compound H affects arterial stiffening and hypertension in aged mice.

Methods & Results

– Aged mice (24‐30 months) were treated with or without compound H (15 mg/kg, IP daily) for 2 weeks, and adult mice without treatments were used as controls (12 months). Pulse wave velocity (PWV), a direct measure of arterial stiffness, and blood pressure (BP) were increased significantly in aged mice. Compound H reversed aging‐related increases in PWV and BP within 2 weeks of treatment. Compound H effectively increased secreted klotho levels in both kidney and serum. Aging‐related arterial stiffness was associated with increased collagen and decreased elastin contents in the media of aortas. In addition, the expression of MMP2, MM9, and TGFb1 was increased in aortas of aged mice. These changes were attenuated by compound H.

Conclusion

Aging‐related arterial stiffening and hypertension are attributed, at least in part, to klotho deficiency. Compound H increases klotho expression and attenuates arterial stiffening and hypertension in aged mice.
Angiotensin II‐Induced Erectile Dysfunction Prevented By Bradykinin B1 Receptor Antagonism
Authors: McCormick Brittney , Huot‐Marchand Julie‐Emilie , Carrol Chad , Carrier Serge , deBlois Denis , Hale Taben
Published: June 2021

Chronic angiotensin II (AngII) treatment induces erectile dysfunction in rats. In penile erectile tissue, AngII stimulates smooth muscle contraction leading to detumescence, while bradykinin promotes relaxation to facilitate erection. AngII has been shown to increase bradykinin B1 receptor (B1R) expression in aorta however; an interaction between these systems has not been examined in erectile tissue. This study investigated the impact of bradykinin B1R antagonism on AngII‐induced erectile dysfunction. Sprague‐Dawley rats were treated with vehicle or AngII in the presence or absence of the B1R antagonist R‐954. After 4weeks, arterial pressure (MAP) and erectile function were assessed in anesthetized rats. AngII increased MAP and left ventricular mass, and significantly impaired erectile function relative to control. While concomitant B1R antagonism had no impact on AngII‐induced hypertension, it prevented the cardiac hypertrophy and erectile dysfunction. Impaired erectile responses were not associated with changes in cavernosal collagen content, ROS production, or endothelial NOS or SMAD2/3 expression. This study reveals for the first time that bradykinin B1R blockade can offset AngII‐induced erectile dysfunction independent of hypertension and unrelated to cavernosal tissue remodeling. Future studies will investigate mechanisms underlying this effect and provide insight into the inter‐regulation of the RAS and kallikrein kinin system in erectile function.

Funding: APS STRIDE program (NHLBI; 1 R25 HL115473‐01), CMSHC
Deficiency of Senescence Marker Protein‐30 Impairs Collateral Growth by Supressing Nitric Oxide Bioactivity under Ischemia
Authors: Yamauchi Hiroyuki , Owada Takashi , Saitoh Shu‐ich , Takeishi Yasuchika
Published: June 2021

Aging impairs collateral growth under ischemia and reduces the expression of VEGF, however the exact mechanism is unclear. Senescence marker protein‐30 (SMP30) decreases with aging. Mice with SMP30 deficiency, a model of aging, have a short lifespan with increased oxidant stress. To elucidate the effect of SMP30 on ischemia‐induced collateral growth, we examined the recovery of cutaneous blood flow (CBF) after femoral artery ligation by laser Doppler imaging in mice. Recoveries of CBF and tissue capillary density were suppressed in SMP30 knockout (KO) mice compared to those of wild type (WT) mice. Acetylcholine (ACh, 1 µM)‐induced NO generation in aorta of SMP30 KO mice was lower than those of WT mice. Superoxide generation and NADPH oxidase activity were greater in aorta of SMP30 KO mice compared to that of WT mice (superoxide level: 3.3±0.5 vs. 1.6±0.2 nmol/mg protein; NADPH oxidase activity: 3240±254 vs. 982±106 RLU; P<0.01, respectively). VEGF content in the biceps femoris muscle in SMP30 KO mice did not increase in 14 days post‐ischemia compared to that in pre‐ischemia (SMP30 KO mice 1.1±0.2 fold vs. WT mice 2.2±0.3 fold, P<0.01). Akt phosphorylation in the biceps femoris muscle was attenuated in SMP30 KO mice compared to that of WT mice (p‐Akt/Akt: SMP30 KO mice 0.4±0.3 vs. WT mice 1.2±0.4, P<0.01). Thus, SMP30 deficiency exacerbates oxidant stress due to NADPH oxidase activation and impairs eNOS activity, which leads to rarefaction of collateral growth induced by ischemia related to Akt‐VEGF pathway. These results suggest that the decrease of SMP30 in aging impairs VEGF/NO‐dependent angiogenesis associated with overproduction of superoxide.
Conditional knockout of smooth muscle‐specific Na/Ca exchanger type‐1 causes striking impairment of NO/cGMP‐mediated vasodilation
Authors: Wang Youhua , Chen Ling , Li Meng , Cha Helen , Iwamoto Takahiro , Zhang Jin
Published: June 2021

The functions of smooth muscle (sm) Na/Ca exchanger (NCX) in the vasculature are controversial and poorly understood. To determine the possible roles of NCX in the vasculature, we developed a novel mouse model (SM‐NCX1 KO) in which the sm‐specific NCX type‐1 (NCX1) was conditionally knocked out using tamoxifen‐inducible Cre‐loxP recombination technique. SM‐NCX1 KO mice exhibit significantly lower blood pressure (BP) and attenuated Ang II‐salt‐induced hypertension (radio telemetry). Isolated, pressurized mesenteric small arteries from SM‐NCX1 KO mice, compared to control arteries, were characterized by: 1) ~90% reduced NCX1 protein expression; 2) attenuated myogenic reactivity; and 3) attenuated vasoconstrictor response to phenylephrine but not angiotensin II; 4) normal relaxation to nifedipine, iberiotoxin, and external Ca2+ removal; but 5) significantly deteriorated endothelium‐dependent vasodilatory responses to acetylcholine, which could not be rescued by exogenous NO/cGMP donor, sodium nitroprosside or 8‐Br‐cGMP. The vasodilation in control arteries was also significantly blocked by lowering [Na+]o and was enhanced in arteries from mice that overexpress sm‐specific NCX1. These findings suggest that 1) sm NCX1 activity is required (viz. downstream modulator) for endothelium‐dependent NO/cGMP‐mediated vasodilation; 2) arterial NCX1 mediates net Ca2+ influx that helps maintain basal vascular tone in small resistance arteries and BP under physiological conditions; 3) NCX1 contributes to the BP elevation in Ang II‐salt hypertension.
Healthy Aging does not Alter Sympathetic Drive during Whole‐Body Passive Heating
Authors: Gagnon Daniel , Schlader Zachary , Crandall Craig
Published: June 2021

Increased muscle sympathetic nerve activity (MSNA) during heat stress in young humans likely reflects the sympathetic drive responsible for the cardiovascular adjustments that facilitate an increase in skin blood flow. In contrast, cardiovascular adjustments during heat stress are attenuated in the aged, and could therefore be due to a lower sympathetic drive. We compared plasma epinephrine ([E]) and norepinephrine ([NE]), as well as MSNA in 11 young (Y: 28 ± 4 y) and 8 aged (A: 71 ± 5 y) subjects prior to and during passive heat stress. A cold pressor test (CPT) was superimposed upon heating to assess if a ceiling in MSNA was attained. Baseline MSNA burst frequency (15 ± 7 vs. 29 ± 4 bursts/min, p=0.01) and burst incidence (26 ± 13 vs. 46 ± 8 bursts/100 c.c., p<0.01) were greater in the aged. Heat stress increased core temperature to a similar extent in both groups (Y: +1.2 ± 0.1 vs. A: +1.2 ± 0.1°C, p=0.99). Changes in plasma [E] (Y: +21 ± 38 vs. A: ‐2 ± 37 pg/mL, p=0.24) and [NE] (Y: +182 ± 127 vs. A: +113 ± 156 pg/mL, p=0.32) with heating did not differ between groups. MSNA burst frequency (47 ± 10 vs. 61 ± 16 bursts/min, p<0.01) and burst incidence (48 ± 14 vs. 65 ± 12 bursts/100 c.c., p=0.01) remained greater in the aged during heating, although both increased similarly between groups (p>0.1). The CPT further increased MSNA burst frequency (Y: +11 ± 11 vs. A: +8 ± 5 bursts/min) and burst incidence (Y: +9 ± 11 vs. A: +10 ± 9 bursts/100 c.c), to a similar extent between groups (p>0.1). These data suggest that the aged do not have a lower sympathetic drive during whole‐body passive heat stress. Funded by NIH HL61388.
Effect of Pregnancy on Sympathetic and Peripheral Vascular Responses to the Cold Pressor Test
Authors: Wakefield Paige , Usselman Charlotte , Stickland Michael , Chari Radha , Julian Colleen , Davenport Margie , Steinback Craig
Published: June 2021

Little is known regarding sympathetic neurovascular regulation during pregnancy. We hypothesized that, despite elevated muscle sympathetic nerve activity (MSNA; peroneal microneurography) in normotensive pregnant women (NP) versus non‐pregnant controls (CT), neurovascular transduction would be blunted in NP, resulting in similar mean arterial pressure (MAP) between groups. Integrated MSNA was obtained during 3 min of rest and 3 min of reflex sympathetic activation (cold pressor test; CPT). Total peripheral resistance (TPR; MAP/Q) and burst frequency (BF) were used to calculate neurovascular transduction (TPR/BF). CPT data were analyzed in 30s bins; the bin corresponding to the highest BF value was selected for analysis. Baseline MAP and TPR were not different between NP vs CT (90±16 vs 90±5 mmHg,P=0.9 and 12±2 vs 13±2 mmHg/L/min, P=0.5, respectively) whereas BF (36±7 vs 24±2, P<0.01) and total MSNA (BF x normalized burst amplitude; 1743±286 vs 1145±191, P<0.01) were higher and neurovascular transduction lower (0.3±0.1 vs 0.5±0.1, P=0.01) in NP. During CPT, BF and total MSNA were higher in NP vs CT (56±17 vs 34±10, P=0.03; 2677±650 vs 1529±515, P=0.01), while no differences in MAP or TPR were observed between NP vs CT (99±24 vs 101±7, P=0.8; 13±4 vs 13±3, P=0.7). Neurovascular transduction during CPT was lower in NP than CT (0.24±0.10 vs 0.40±0.07, P=0.01), indicating a vascular adaptation to pregnancy. Supported by WCHRI, NSERC & University of Alberta Human Performance Scholarship Fund.
Role of NaV 1.7 channels on skeletal muscle afferents in evoking the exercise pressor reflex
Authors: Stone Audrey , Copp Steven , Kaufman Marc
Published: June 2021

Voltage gated sodium channels (NaV) 1.7 can be blocked by tetrodotoxin (TTX) in concentrations of 300nM or less. Moreover, NaV 1.7 channels are highly expressed in sensory neurons and are thought to play a role in inflammatory pain. These findings prompted us to determine in decerebrated, unanesthetized rats, the role played by NaV 1.7 channels on the axons of thin fiber muscle afferents in evoking the exercise pressor reflex. We first showed that application of 50nM tetrodotoxin to the L3‐L5 dorsal roots attenuated the exercise pressor reflex evoked by statically contracting the hindlimb muscles. The peak pressor responses to static contraction were significantly attenuated by TTX and were restored by replacing the TTX solution with Lactated Ringer's solution (control: 21±1 mmHg, TTX: 8±2 mmHg, restored: 21±3 mmHg; n=6; p<0.01). Likewise, the peak cardioaccelerator responses to contraction were significantly attenuated by TTX (control: 12±3 bpm, TTX: 5±2 bpm, restored: 8±2 bpm; n=6; p<0.05). Similar tensions were developed for each contraction. We next applied the specific NaV 1.7 channel inhibitor, Ssm6a (100nM), to the L3‐L5 dorsal roots to attenuate the reflex. We found that the peak pressor responses to contraction were significantly attenuated by Ssm6a and were restored by replacing the Ssm6a solution with Lactated Ringer's solution (control: 19±3 mmHg, Ssm6a: 10±1 mmHg, recovery: 19±4 mmHg; n=6; p<0.05). In contrast, the peak cardioaccelerator responses to contraction were not attenuated by Ssm6a. Similar tensions were developed for each contraction. We conclude that NaV 1.7 channels, which are TTX‐sensitive, play a role in the afferent pathway evoking the exercise pressor reflex. Funding: NIH AR‐059397
IL‐6 Administration Increases the Exercise Pressor Reflex
Authors: Copp Steven , Stone Audrey , Kaufman Marc
Published: June 2021

IL‐6 is both a pro‐inflammatory cytokine released from macrophages as well as an anti‐inflammatory myokine released from contracting skeletal muscle. Administration of IL‐6 and the soluble form of its receptor (sIL‐6r) has been shown to increase peripheral afferent excitability in response to noxious stimuli. That finding prompted us to test the hypothesis that in decerebrate, unanesthetized rats co‐injection of 50 ng IL‐6 and 50 ng sIL‐6r into the arterial supply of the hindlimb would increase the exercise pressor reflex. We found that after 1 hr co‐injection of IL‐6/sIL‐6r (n=8) modestly increased the peak pressor responses to static (control: 13.5±2.6 mmHg, IL‐6/sIL‐6r: 17.3±2.4 mmHg; p<0.05) and intermittent (control: 9.6±1.9 mmHg, IL‐6/sIL‐6r: 15.3±3.8 mmHg; p<0.05) contractions of the hindlimb muscles. Co‐injection of IL‐6/sIL‐6r had no effect on the peak cardioaccelerator or the popliteal artery blood flow responses to static or intermittent hindlimb muscle contractions. Tension‐time indices were similar between control and IL‐6/sIL‐6r. In five additional rats intra‐arterial hindlimb injection of 50 ng of soluble gp130, which neutralizes the actions of IL‐6/sIL‐6r, prevented the IL‐6/sIL‐6r‐induced increases in the peak pressor responses to static (control: 15.8±3.1 mmHg, sgp130+IL‐6/sIL‐6r: 13.4±2.0 mmHg; p>0.05) and intermittent (control: 10.4±1.8 mmHg, sgp130+IL‐6/sIL‐6r: 9.3±2.2 mmHg; p>0.05) contractions. Moreover, intravenous injection of 50 ng of IL‐6/sIL‐6r (n=4) had no effect on the peak pressor responses to static or intermittent hindlimb muscle contractions. We conclude that IL‐6/sIL‐6r co‐injected into the arterial supply of the hindlimb increased the exercise pressor reflex evoked by static and intermittent hindlimb muscle contractions. Funding: NIH HL‐096570, AR‐059397.
Exercise preconditioning protects against traumatic brain injury in rats by upregulating neuronal and astroglial heat shock protein 72
Authors: Chen Yu‐Chien , Chio Chung‐Ching , Liu Yu‐Fan , Chang Ching‐Ping
Published: June 2021

Evidence suggests that heat shock protein 72 (HSP72) serves as an important endogenous neuroprotective response after traumatic brain injury (TBI). Our study is the first to explore the neuroprotective effects of exercise preconditioning, an inducer of HSP72, in a clinically relevant experimental TBI model in rats. It was found that exercised rats (given pre‐TBI exercise) had significantly higher levels of neuronal and astroglial HSP72, a lower functional deficit, fewer brain contusion and lower apoptotic cells than did non‐exercised animals. pSUPER plasmid expressing hsp72 interfering RNA (siRNA‐hsp72) was injected into the injured brain tissues. In addition to reducing neuronal and astroglial HSP72, the siRNA‐hsp72 significantly reduced the beneficial effects of exercise preconditioning in attenuating beneficial effects of exercise preconditioning in reducing functional deficits as well as brain contusion and apoptosis. We conclude that exercise preconditioning is a promising strategy for facilitating functional recovery form TBI in rats.
In vivo Skeletal Muscle Function and Doxorubicin Treatment in the Rat
Authors: Hydock David , Omar Asma , Bredahl Eric , Quinn Colin
Published: June 2021

The chemotherapy drug doxorubicin (DOX) has been shown to cause skeletal muscle dysfunction when measured ex vivo, but little is known about the effects of DOX on in vivo skeletal muscle function. The aim of this study was to examine the effects of two different bolus DOX treatments on skeletal muscle function measured in vivo using a rat grip strength meter. Baseline grip strength was assessed prior to rats receiving intraperitoneal injections of 10 mg/kg DOX (DOX1), 15 mg/kg DOX (DOX2), or saline as a control (CON). Grip strength was then assessed daily for seven days. At baseline, no between group differences in grip strength were observed, but a between group difference was observed at day four with DOX2 having a lower grip strength than CON and DOX1. This reduced grip strength in DOX2 continued through day seven. DOX1 had reduced grip strength when compared to CON only at day six. These results suggest that DOX administration affects in vivo skeletal muscle function in a dose‐dependent manner. As such, this model provides a novel approach for analyzing DOX myotoxicity and interventions aimed at minimizing this side effect.