bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinct Functions of Vascular Endothelial and Smooth Muscle PPARγ in Regulation of Blood Pressure and Vascular Tone
Authors: Wang Ningning , Symons John D. , Zhang Hui , Yang Guangrui , Jia Zhanjun , Gonzalez Frank J. , Litwin Sheldon E. , Soodvilai Sunhapas , Yang Tianxin
Published: June 2021

PPARγ activator rosiglitazone exhibit anti‐hypertensive and vasculoprotective effects. To study the vascular function of PPARγ, disruption of PPARγ in vascular smooth muscle cells and in endothelial cells were generated by crossing PPARγ floxed (fl/fl) mice with SM22‐Cre and Tie2‐Cre mice, respectively (termed SM KO and EC KO). Despite normal 24‐h MAP values, the circadian variation of Bp was reduced by 35% (P<0.05) in SM KO mice and by 33% (P<0.05) in EC KO mice. This reduction was due to an elevated day‐time MAP in SM KO mice but a reduced night‐time MAP in EC KO mice. Rosiglitazone induced a similar Bp lowering effect in DOCA‐salt treated fl/fl (139.2 ± 2.7 vs. 126.1 ± 2.9 mmHg, P<0.05), SM KO (137.4 ± 2.1 vs. 126.2 ± 3.2 mmHg, P<0.05), as well as collecting duct‐specific KO mice while EC KO mice were resistant to this effect (133.29 ± 3.48 vs. 131.12 ± 2.6 mmHg, P>0.05). The femoral arteries lacking EC PPARγ exhibited increased reactivity to different vasoconstrictors without a significant alteration in acetylcholine‐induced relaxation. However, the vasculature lacking VSMC PPARγ had blunted sensitivity to α1‐adrenergic agents but enhanced sensitivity to Ach. Our results demonstrated a novel role of vascular PPARγ as a peripheral factor participating in regulation of circadian rhythm of Bp. Additionally, TZD‐induced Bp lowering is dependent on EC but not VSMC PPARγ, likely through a mechanism involving attenuation of vasoconstriction.
Long‐term recording of renal sympathetic nerve activity in conscious rats via telemetry
Authors: Van Vliet Bruce N. , Guild Sarah‐Jane , Barrett Carolyn , McBryde Fiona , Malpas Simon
Published: June 2021

We have established a method for recording renal sympathetic nerve activity (RSNA) by radio‐telemetry in conscious rats. Telemeters with appropriate high sensitivity and bandwidth (model TR46S, Telemetry Research, Auckland, NZ) were implanted in the abdominal cavity under isoflurane anesthesia. Electrode wires were secured to the renal nerves using a rapidly setting silicone elastomer via a retroperitoneal approach. In some cases, a blood pressure telemeter (TA11PaC40, Data Sciences, Minneapolis, MN) was also installed in the peritoneal cavity.

In conscious rats, RSNA exhibited pulse synchronous activity, was abolished by ganglionic blockade (15–50 mg/kg pentolinium), and was greatly activated by the nasopharyngeal reflex response to smoke. High quality recordings could be routinely obtained for 1 to 2 weeks, but in some cases were found to continue working (e.g. as long as 98 days) when left longer. Application of this method will allow us to investigate the regulation of RSNA and its contribution to long‐term blood pressure control in freely behaving rats. Supported by grants from the Canadian Institutes of Health Research and the Health Research Council of New Zealand.
Pressor responses produced by peripheral osmoreceptor activation in commissural nucleus of the solitary tract‐lesioned rats.
Authors: Blanch Graziela Torres , Freiria‐Oliveira Andre Henrique , Colombari Eduardo , Menani Jose Vanderlei , Colombari Debora Simoes Almeida
Published: June 2021

Previous studies demonstrated that intragastric (ig) 2 M NaCl load (that activates peripheral and central osmoreceptors) produced increases in mean arterial pressure (MAP) and enhanced dipsogenic responses in commissural nucleus of the solitary tract (commNTS) lesioned rats. Lesions of commNTS also increased water intake produced by ig 0.6 M NaCl load (that activates peripheral, not central, osmoreceptors ‐ Am. J. Physiol., 269: R 1085, 1995), which suggests that commNTS mechanisms inhibit peripheral osmoreceptor‐induced thirst. In the present study we investigated the effects of ig 0.6 M NaCl load on MAP and heart rate (HR) in commNTS lesioned rats. Male Holtzman rats (300–330 g, n = 5–8/group) with chronic (15 days) sham or electrolytic lesions (1 mA, 10 s) of the commNTS were used. MAP and HR were measured 60 min before and 60 min after ig 0.6 M NaCl load (2 ml). Plasma Na+ concentration was analyzed after ig 0.15 M or 0.6 M NaCl in the same animals, 3 days after MAP and HR recordings. Ig 0.6 M NaCl induced pressor responses in commNTS lesioned rats (11 ± 3 mmHg), but did not affect MAP in sham rats (−3 ± 2 mmHg) or HR in both groups. Ig 0.6 M NaCl produced no change on plasma Na+ concentration in sham (142 ± 3 vs. 0.15 M NaCl: 140 ± 1.2 mEq/l) or in commNTS lesioned rats (144 ± 0.4 vs. 0.15 M NaCl: 141 ± 1 mEq/l). The results suggest that similar to water intake, commNTS mechanisms also inhibit peripheral osmoreceptor‐induced pressor responses.

Supported by: FAPESP, CNPq.
Long‐term recording of sympathetic nerve activity in conscious rats using telemetry
Authors: Burris Sarah Kimberly , Knuepfer Mark M
Published: June 2021

Increased sympathetic nerve activity (SNA) is believed to contribute to the development of cardiovascular disease. Since short‐term recordings can't predict long‐term changes in SNA, longer recordings are required. Our study describes a high resolution (8 kHz) telemetry system (www.telemetryresearch.com) that allows chronic recording of SNA in conscious rats. We instrumented rats with renal SNA transmitters and femoral cannulas and repeatedly recorded SNA and arterial pressure (AP) responses to acute cold water stress, to pharmacological stress with cocaine, to baroreceptor stimuli (phenylephrine and nitroprusside), and to ganglionic blockade with trimethaphan to assess background activity. A patented inductive power transfer technique allowed the transmitter to recharge while in the conscious animal. Responses to stressors included reproducible changes in renal SNA corresponding to AP. After 2 weeks, SNA was recorded in most rats studied (75%). Signal to noise ratio, assessed with trimethaphan (10 mg/kg), did not change significantly over the course of two weeks (day 2 SNA decreased 41±5%, day 14 decreased 30±4%). This study demonstrates the ability to record renal SNA for at least two weeks in conscious rats using telemetry. We suggest this technique could provide novel insight into the role of SNA in the development of cardiovascular disease. Supported by USPHS DA13256.
Influences of dehydration and angiotensin receptor blockade on control of sympathetic nerve activity in healthy humans
Authors: Sharpe Emily Elizabeth , Strom Nicholas A , Roberts Shelly K. , Kingsley‐Berg Shirley , Curry Timothy B , Eisenach John H. , Charkoudian Nisha
Published: June 2021

Dehydration in humans decreases orthostatic tolerance and alters sympathetic neural control of the circulation, but the mechanisms involved are unclear. Our goal was to evaluate the role of angiotensin II (AngII) in altering the sympathetic control mechanisms in dehydration. We hypothesized that dehydration would increase resting muscle sympathetic nerve activity (MSNA) and increase sensitivity of baroreflex control of MSNA and that these changes are mediated in part by AngII via AT1 receptors. We measured resting MSNA and baroreflex control of MSNA in healthy young adults under two conditions: euhydration and dehydration after 24 hr fluid restriction. We continuously measured heart rate (ECG), beat‐to‐beat blood pressure (Finometer), central venous pressure (peripherally inserted central catheter) and MSNA (peroneal microneurography) in both conditions. In each condition, measurements were taken before and after 50 mg losartan (AT1 antagonist). Dehydration was associated with a ~52 % increase in resting MSNA, but losartan did not consistently influence resting MSNA. Contrary to our hypothesis, baroreflex sensitivity increased ~39 % following losartan administration during dehydration. Our results confirm the sympathoexcitatory influence of dehydration, but the role of AngII in this process requires further evaluation.

Supported by AHA 0750036Z and NIH CTSA UL1‐RR24150.
T3 improves left ventricular function in a rodent model with a myocardial infarction
Authors: Henderson Kyle K , Danzi Sara , Klein Irwin , Samarel Allen M
Published: June 2021

Serum triiodothyronine (T3) concentration is reduced in patients with congestive heart failure which may contribute to the altered expression of thyroid hormoneresponsive genes. We hypothesize that T3 supplementation in a rat model of left ventricular (LV) dysfunction will increase α/β myosin heavy chain (MHC) ratio, sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) expression, and thereby improve LV function. Echocardiography was used to assess LV structure and function in male Sprague Dawley rats (~300g), before and after left anterior descending coronary artery ligation. One week post‐ligation, LV function was significantly attenuated; ejection fraction was reduced from 38±1% to 21±1%. Saline control or T3 supplementation was then started at 3, 6 and 60μg/kg/day for 8wks. Radiotelemetry was used to measure body temperature, ECG, and arterial blood pressure in a subset of animals. LV structure and function, at 2, 4, 6 and 8wks were not changed by T3 supplementation as measured by echocardiography. However, LV catheterization at 8wks demonstrated that animals receiving T3 supplementation at 6 or 60μg/kg/day had significantly greater LV contractility (+dP/dt) and a trend toward improved LV relaxation (Tau). LV RNA was extracted for measurement of α and β MHC and SERCA mRNA. These findings support the hypothesis that T3 supplementation may improve the function of the remaining viable LV tissue in rats with a myocardial infarction. Funding: Ralph and Marian Falk Medical Research Trust and King Pharmaceuticals.
Effect of Protein Kinase C inhibitor on angiogenesis in diabetic mice
Authors: Kenmochi Reiko , Matsushita Shonosuke , Sugimori Haruhiko , Sato Fujio , Sakakibara Yuzuru
Published: June 2021

Purpose: The outcome from therapeutic angiogenesis in diabetes mellitus (DM) is not satisfactory compared with non‐DM patients. In diabetes, protein kinase C (PKC) is activated according to intracellular high glucose concentration. And activated PKC is closely related to progression of diabetic microangiopathy. Recently, it was reported that blockade of PKC brought about beneficial effects on diabetic microangiopathy. From these backgrounds, we investigated effect of PKC inhibitor (bisindolylmaleimide: Bis) on angiogenesis in diabetic mice. Methods: Type I diabetes was induced by intraperitoneal administration of streptozocin (50mg/kg) for seven days in mice. After establishment of DM, Bis was injected ten days intraperitoneally (10 nM/day). Resection of femoral artery was conducted to develop hindlimb ischemia and erythropoietin (1,000 IU/kg, i.p.) was injected at the operation in all mice. Mice were divided into three groups (each n=6): Group A; DM(+) and Bis (−), Group B; DM(+) and Bis(+), Group C; DM(−) and Bis (−). Two weeks after the procedure, gastrocnemius muscles were resected. Vascular density and size of capillary vessels were compared by use of light microscopy in each group. Result: Vascular density of Groups A, B, C is as follows: 6.5+/−1.7, 11.0+/−3.5, 13.8+/−2.2 (per high power field), respectively (p<0.001; Group A vs. Group C, p<0.05; Group A vs. Group B). Conclusion: PKC inhibitor improved capillary density in Epo‐induced angiogenesis in diabetic mice. The use of PKC inhibitor may improve the clinical results of therapeutic angiogenesis in diabetic patients.
Connexin Protein Expression During Early Ischemic Remodeling with Femoral Artery Ligation
Authors: Wolfert Madeline , Ambrecht Lindsay , Raphael Cara , Looft‐Wilson Robin
Published: June 2021

The vascular system remodels in response to ischemia by stimulating angiogenesis. This process may involve intercellular communication via gap junctions, composed of connexin proteins (Cx43, Cx40, Cx37), although the specific role of gap junction communication, and associated connexin expression, in blood vessels undergoing angiogenesis has not yet been elucidated. Using a mouse model of hindlimb ischemia, femoral artery ligation, the femoral artery was removed in female mice (age=22–39 wk) between the inguinal ligament and popliteal bifurcation. A sham surgery was performed on the opposite leg. Animals recovered for 24 hr or 3 d, were anesthetized, and the gastrocnemius muscles were removed. Immunoblotting revealed significantly (p<0.05) greater phosphorylation of eNOS on serine‐1179 (mean ± SD: 48.1 ± 37.5 % increase, n=4) at 24 hr in the experimental muscle versus sham, a difference no longer present by the third day post‐surgery. Cx43 protein decreased by 41.5 ± 10.5 % when normalized to gapdh (p=0.06, n=3) and by 52.8 ± 18.2% when normalized to total protein (p<0.05, n=3) at 24 hr in the experimental muscle. There were no differences in Cx37 at 24 hr or Cx43 or Cx37 at 3 d. We previously found no significant differences in Cx43, Cx40, or Cx37 mRNA in this tissue during these same time periods post‐surgery. Together with the current data, we conclude that vascular connexins are generally stable during acute ischemic remodeling, but Cx43 may be acutely down‐regulated post‐transcriptionally. Supported by NHLBI and HHMI‐UBSEP.
Overexpression of caveolin‐3 in adult cardiac myocytes reduces reactive oxygen species generation
Authors: Jennings Michelle , Niesman Ingrid R , Insel Paul A , Roth David M , Patel Hemal H
Published: June 2021

Caveolae are cholesterol‐, sphingolipid‐ and caveolin enriched membrane microenvironments that localize signaling molecules, a subset of which include redox‐sensitive enzymes. Ischemia/reperfusion results in increased generation of reactive oxygen species (ROS). The role of caveolae in regulation of ROS is not clear. We hypothesize that caveolae may be enriched in reductive enzymes such that over‐expression of caveolin‐3 in cardiac myocytes will increase caveolae formation and enhance the buffering of ROS. Adult rat cardiac myocytes (ACM) were isolated and incubated with adenovirus for caveolin‐3 (Adv.Cav‐3) or Adv.LacZ as control. After 48 hours incubation with virus, myocytes were fractionated on a sucrose density gradient or preloaded with dihydroethidium (DHE, a fluorescent sensor for superoxide) and subjected to hypoxia (oxygen glucose deprivation, 1 h)/reperfusion (20 min). Cellular ROS generation was assessed by microscopy or a plate reader assay. Adv.Cav‐3‐treated ACM had increased expression of Cav‐3 and MnSOD in sucrose density gradient fractions and decreased DHE fluorescence compared to the controls, suggesting that Cav‐3 over‐expression increases buffering of ROS. These results imply that caveolae via enrichment of reductive enzymes are domains that buffer cellular ROS in cardiac myocytes and perhaps other cell types. (Supported by grants for NIH and AHA)
Atomic force microscopy (AFM) analysis of lipid peroxidation following hyperoxia and hydrogen peroxide treatment in human U87 glioblastoma cells
Authors: D’Agostino Dominic P , Olson James E , Dean Jay B
Published: June 2021

The atomic force microscope (AFM) is capable of resolving the plasma membrane with nanometer resolution. In this study we used the AFM to characterize hyperoxia‐induced oxidative damage to changes in the plasma membranes of cultured human glioma cells (U87). U87 cells were exposed to 0.20 ATA O2, normobaric hyperoxia (0.95 ATA O2) or hyperbaric hyperoxia (HBO2, 3.25 ATA O2) for 30 min. In separate experiments H2O2 (200 μM and 2 mM) was used as a positive control. Malondialdehyde (MDA) was measured to confirm lipid peroxidation. Following treatment, the cells were fixed with 2% glutaraldehyde and scanned in air or fluid. Individual cells from each group (n = 35 to 45 cells/group) were scanned and analyzed to assess average membrane roughness (Ra). The Ra of the plasma membrane was 34 ± 3 nm, 57 ± 3 nm and 63 ± 5 nm in 0.20 ATA O2, 0.95 ATA O2 and HBO2, respectively. In H2O2 treated cells Ra was 28 ± 4 nm, 56 ± 7 nm and 138 ± 14 nm in air (air in 5% CO2), 200 μM and 2 mM H2O2. Co‐treatment with antioxidant Trolox C (150 μM) significantly reduced Ra during exposure to hyperoxia and H2O2, suggesting that the amount of membrane blebbing was proportional to the level of oxidative stress. Furthermore, measurement of MDA confirmed that H2O2 and hyperoxia increased lipid peroxidation, suggesting that membrane blebbing is related to oxidative stress. In conclusion, these data demonstrate oxidative damage from lipid peroxidation increases with oxygen concentration.
Serotonin produces MAO dependent oxidative stress in human heart valves
Authors: Silva Ricardo Alfonso Pena , Miller Jordan D , Heistad Donald D
Published: June 2021

Serotonin (5HT) from carcinoid tumors and drugs (fen‐phen interactions) may contribute to development of valvulopathies and pulmonary hypertension. We determined whether 5HT induces oxidative stress in human heart valves, and examined mechanisms that may produce ROS. Superoxide (O2•−) was measured in heart valves from explanted human hearts that were rejected for transplantation. Superoxide levels (lucigenin‐enhanced chemoluminescence) were increased in valves and pulmonary artery after incubation with 5HT. Inhibitors of 5HT1 (GR55562) and 5HT2 receptors (ketanserin), and a selective serotonin reuptake blocker (fluoxetine) surprisingly did not prevent increases in superoxide. DPI (non‐specific inhibitor of flavin‐containing enzymes), tranylcypromine and clorgiline (inhibitors of MAO) abolished the increase in O2•−. Apocynin (inhibitor of NAD(P)H oxidase) and catalase did not prevent increase in O2•−. Addition of 5HT to human recombinant purified MAO‐A generated superoxide, and this effect was inhibited by a MAO inhibitor.

Conclusion: Superoxide is increased in human vessels and heart valves exposed to high levels of 5HT by a mechanism that is independent of 5HT receptors. MAO is functional in the heart valves and mediates the increase in O2•− induced by serotonin.
Detection of exhaled sulfide gas: a potential in vivo, continuous monitoring technique for therapeutic sulfide donor compounds
Authors: Insko Michael , Deckwerth Thomas , Szabo Csaba
Published: June 2021

IK‐1001 is a parenteral sulfide donor that recently entered human clinical trials. Current methodology to measure blood sulfide involves chemical derivatization or detection via electrodes. Hewe we have established a method to detect sulfide concentrations in exhaled air. Male rats were anesthetized with ketamine and instrumented with intravenous catheters and pneumotachometers. The sampling port of the pneumotachometer was directed to a sulfide gas detector (Interscan, Chatsworth, CA) with a sensitivity range of 5 to 0.05 ppm. IK‐1001 was infused intravenously while the airway was monitored for exhaled sulfide. Exhaled sulfide became detectable with infusions of 0.3 mg/kg/min and higher and the concentration increased in proportion up to 1.2 mg/kg/min. After correction for sample dilution arising from the sampling rate of the sulfide detector (500 mL/min) greatly exceeding minute respiration in rats (145 – 175 mL/min), exhaled sulfide concentration was estimated to range from 0.2 to 14 ppm over the tested infusion rates. Quantification of exhaled gas in comparison to sulfide equivalents administered indicates exhaled sulfide is approximately 0.1 to 2% of the infused dose. We conclude that monitoring exhaled sulfide may be a useful means of detecting and quantifying sulfide exposure during therapy with sulfide donor compounds.
Brief Exposure to Intracoronary Bradykinin at Reperfusion Limits Infarct Size in Isolated Rabbit Hearts by a Mechanism That Involves Both Free Radical Production and PKC
Authors: Davis Amanda Marie , Downey James M. , Cohen Michael V.
Published: June 2021

Bradykinin given at reperfusion following ischemia reduces infarct size. We determined if PKC and free radicals, signaling components involved in ischemic postconditioning, are also used by bradykinin. We also determined the minimum bradykinin infusion time required to be protective. Isolated rabbit hearts underwent 30 min coronary branch occlusion followed by 2h of reperfusion. 100 nM bradykinin was included in the perfusate for the first 60 min of reperfusion. Antagonists, when used, were present for the first 20 min of reperfusion. Bradykinin reduced infarct size from 32±4% of the risk zone in control to 11±3% (P<0.05). The scavenger 2‐mercaptopropionyl glycine (MPG), 300 uM, blocked bradykinin's protection (31±4%). The PKC antagonist chelerythrine (2.8 uM) also abrogated protection (29±3%). Infusing bradykinin for 15 min was still protective (17±3%). However, only 7 min of bradykinin did not protect (30±5%). We conclude that, like postconditioning, protection from bradykinin at reperfusion involves both redox signaling and PKC activation. While bradykinin may be too hypotensive to use intravenously, this drug could be given directly into a patient's coronary artery following percutaneous coronary intervention since the heart only needs to be exposed to bradykinin for 15 min. Work funded by NIH grant: HL 020648.
Opening of Mitochondrial KATP Channel Improving Long‐Term Hypothermic Preservation Heart by upregulation of HSP 70 protein
Authors: Zhang Shu‐luo , Fang Shan , OU Ying , Zhu Li , Chen Ying‐ying , Shen Yue‐liang
Published: June 2021

The aim of this study is to investigate the mechanism of cardioprotective effects of diazoxide, a selective opener of mitochondrial ATP‐sensitive potassium channel (mitoKATP) in preserved heart. The isolated rat heart Langendorff model was used. The hearts were stored in 4°C Celsior solution in the presence or absence of diazoxide for 3, 6 or 9 h followed by 60 min of reperfusion. Apoptotic cardiomyocytes were detected by terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling (TUNEL) method. The expression of heat shock protein 70 (HSP 70) was also evaluated by western blotting analysis. The results showed that the percentage of apoptotic cells increased in a time‐dependent manner after hypothermic preservation. When compared with the 9 h control group, diazoxide (15, 30 or 45 μmol/L) reduced the percentage of apoptotic cells and increased the expression of HSP 70 protein in rat hearts suffered from 9 h of hypothermic preservation in a dosedependent manner. These results indicate that diazoxide could alleviate rat myocardial injury induced by ischemia‐ reperfusion through upregulation of HSP 70 protein expression.

(This work was supported by the National Natural Science Foundation of China (No.30470635))
Testosterone administration induces protection against global myocardial ischemia
Authors: Borst Stephen E , Quindry John C , Yarrow Joshua F , Conover Christine F , Powers Scott K
Published: June 2021

We tested the hypothesis that testosterone (T) treatment affords protection against ischemia/reperfusion (I/R) injury. Orchiectomized (ORX) F344 male rats received 1.0 mg T/day for 21 days or exercise training (EX) for 10 days. Treatment groups were: Sham‐operated, ORX, ORX+T and ORX+EX. At sacrifice, cardiac performance was assessed in a working heart model of I/R (25 minutes of global ischemia and 45 minutes of reperfusion). T increased recovery of aortic flow by 2.2‐fold (p < 0.05) and cardiac work by 2.0‐fold (p < 0.05). ORX reduced recovery of left ventricular developed pressure (LVDP) by 42% (p < 0.05). T increased recovery of LVDP by 2.8‐fold and cardiac contractility (+dP/dt) by 45% (p < 0.05). ORX caused a 2.6‐fold increase in pre‐ischemic cardiac release of lactate dehydrogenase (LDH), an effect that was prevented by T (p < 0.05), but not EX. T reduced post‐ischemic release of LDH release by 45% (p < 0.05). EX caused a 13% increase in cardiac expression of MnSOD and T caused a 28% increase in catalase expression. Glutathione peroxidase (GPX) was not affected by either intervention. ORX reduced serum T by ~98% and T administration elevated T 4.6‐fold over Sham (p < 0.05). Serum estrogen was undetectable in all groups. We conclude that that loss of natural T predisposes the heart to increased contractile dysfunction during I/R, and that high‐dose T confers cardioprotection through yet to be identified mechanism(s).
Local Delivery of an PKCε‐Activating Peptide Improves Ischemic Tolerance in Estrogen Deficient and Aged Rats and Regulates Protective Gene Expression
Authors: Jefferson Sarah Jane , Lancaster Timothy S , Tomicek Nanette J , Korzick Donna H
Published: June 2021

Background: Age is a leading and poorly understood risk factor for the development of acute coronary syndrome in post‐menopausal women. The failed efficacy of estrogen (E2) replacement to confer cardioprotection has spurred interest to identify alternative therapeutic targets. In aged male hearts, selective PKCε activation limits ischemia‐reperfusion (I/R) damage; however, whether acute PKCε activation is sufficient to produce a protected phenotype in aged females is unknown. Purpose: To determine whether local delivery of an PKCε‐activator peptide (ψ∈RACK) reduces I/R damage in aged and E2‐deficient (OVX) female hearts. Methods: LV contractile responses were assessed in Langendorff‐perfused hearts (5 mmHg EDP, 260 bpm, 85 mmHg) from gonad intact and OVX, adult (5–6 mo) and aged (24 mo) F344 rats (n=5–7/group). Prior to I (47 min), hearts were perfused with either Tat‐ψ∈RACK (500 nM) or Tat (500 nM) for 10 min. Infarct size was assessed using triphenyltetrazolium staining and gene transcription through real time PCR (RACK2, CX43 and eNOS). Results: Recovery of LV developed pressure was significantly improved and infarct size reduced by ψεRACK in aged intact and OVX vs age‐matched controls (60% & 80% vs 21% & 33%; p<0.05). RACK2 mRNA was increased in aged but not adult (p<0.05). Conclusions: Our results suggest, for the first time, a central role for PKCε as a potential target to limit I/R damage with aging in females.
Thoracic impedance as a potential indicator of Gz‐induced presyncope
Authors: Howarth Mark S , Moore Fritz B , Hinghofer‐Szalkay Helmut , Jezova Daniela , Diedrich Andre' , Ferris Mead , Schlegel Todd T , Patwardhan Abhijit R , Knapp Charles F , Evans Joyce M
Published: June 2021

We investigated fluid shifts and regulatory responses to variations of posture, exercise, Gz level and radius of rotation in subjects riding NASA Ames’ 20G centrifuge. Results are from 4 protocols that address radius and exercise effects only. Protocol A: After 10 min supine control, 12 healthy men (35 ± 9 yr, 82.8 ± 7.9 kg) were exposed to rotational 1 Gz (2.5 m radius) for 2 min followed by 20 min alternating between 1 and 1.25 Gz. Blood samples were taken pre and post spin. Protocol B: Same as A, but lower limb exercise (70% V02max) preceded ramps to 1.25 Gz. Protocol C: Same as A but radius of rotation 8.3 m. Protocol D: Same as B but at 8.3 m. RESULTS: The 8 subjects who completed all protocols, increased heart rate (HR) from control by: A: 5, B: 39, C: 11, D: 44 bpm; and the 4 who did not: A: 6, B: 35, C: 20, D: 50 bpm. For thoracic fluid volume, (bioimpedance), the 8 subjects changed from control: A: −394, B: −548, C: −537, D: −708 mL; and the 4: A: −516, B: −652, C: −583, D: −1263 mL. The 4 subjects lost more thoracic fluid volume than the 8, especially in protocol D. A slightly greater increase in HR for the 4 compared to the 8 was not adequate to maintain cardiac output during D. Our data support the concept that thoracic impedance can detect inability to return blood to the heart which precedes syncope and therefore predicts presyncope during rest and following (or during) exercise. Supported by NASA EPSCoR WKU52611 and Ames Res. Center.
A potential application of dietary soy protein, aminoguanidine and L‐carnitine as anti‐oxidants in an animal model of simulated microgravity.
Authors: Chowdhury Parimal , Soulsby Michael E. , Ali Nawab , Mehta Rahul
Published: June 2021

The objective of the current study was to determine the effect of antioxidants in rats under simulated microgravity induced by hind‐limb suspension (HLS). Methods: A NASA validated model was used with five groups of rats. L‐carnitine and aminoguanidine were used in the drinking water in rats on Purina chow. A separate group was maintained on a soybean diet. Group 1 was hindlimb loaded control; Group 2 was hindlimb unloaded control, Group 3 was hindlimb unloaded on L‐carnitine (LC), Group 4 was hindlimb unloaded on aminoguanidine (AG), and Group 5 was hindlimb unloaded on 9.6% soybean protein diet. The animals were primed and suspended for fourteen days (total 21 days). At term, the animals were sacrificed. Tissues from brain, heart, lung, liver, stomach, pancreas, small intestine, kidney and testes were harvested. Harvested tissues were extracted for measurements of malondialdehyde (MDA) and glutathione levels. Results: MDA levels in tissues were elevated by suspension (p < 0.05). MDA levels were lower (p< 0.05) in the animals on LC, AG, and the soybean diet, when compared to the hindlimb unloaded control group. Glutathione levels varied between the tissues. Conclusions: Results suggest that LC, AG, and a soybean diet decrease peroxide formation, while tail suspension increases it. Data indicate that LC, AG, and a soybean diet may have a protective role in the reduction of lipid peroxidation damage produced by stress.
Inhibition of Calpain Decreases Muscle Weakness During Unloading
Authors: Salazar Jesus R , Michele Daniel E , Brooks Susan V
Published: June 2021

Unloading skeletal muscle results in atrophy and a decreased ability of the remaining muscle to generate force. Reduced atrophy has been reported when calpain activity is inhibited during unloading, but the impact on force generating capability has not been established. Our hypothesis is that endogenous inhibition of calpain through muscle specific overexpression of calpastatin prevents the loss of mass and the decreased specific force (N/cm2) observed with unloading. Wild type (wt) and calpastatin overexpressing (cp) mice were subjected to hind limb suspension (HS). Following 3, 9, or 14 days of HS, soleus and extensor digitorum longus (EDL) muscles were removed from anesthetized mice and maximum isometric force (Po) was measured in vitro. Compared with muscles of non‐suspended mice, soleus muscles of wt mice showed a 25% loss in mass after only 3 days of HS that was maintained to day 14 and specific Po demonstrated a progressive decline that reached ~30% by day 14. In cp mice, a decrease in specific Po for soleus muscles was not observed until day 14, when the value was only 10% lower than that for muscles of non‐suspended cp mice. EDL muscles were unaffected by HS in either wt or cp mice. We conclude that inhibition of calpain activity by overexpression of calpastatin protects the soleus muscle from atrophy associated with unloading and maintains the integrity of the force generating apparatus. Support from NASA NNCO 4AA21 A.
Effects of a Comprehensive Exercise Training Regimen and KMgCit on Bone Elasticity as an Indicator of Bone Quality after 5 Weeks of Bedrest
Authors: Krainski Felix , Hastings Jeff , Pacini Eric , Richer Edmond , Snell Peter , Palmer Dean , Zerwekh Joseph , Antich Pietro , Levine Benjamin D.
Published: June 2021

We investigated the effects of a multi‐load exercise program and KMgCit supplementation on the preservation of bone quality following 5 weeks of bedrest as measured by ultrasound critical‐angle reflectometry (UCR). The bone elasticity of 35 subjects (26 M, 9 F, 35 ± 10 yrs) was studied before and after bedrest. The subjects were divided into 4 groups: sedentary with no drug (n=12); sedentary with KMgCit (n=11); exercise (n=11); and exercise with KMgCit (n=4). The exercise group underwent intense multi‐joint rowing ergometry (30–45 min/d, 6 d/wk) and resistive strength training (2 d/wk). Subjects receiving the study drug were given 42:21:63 mEq KMgCit a day. Bone elasticity, a correlate of bone strength, was assessed by UCR on the tibia and calcaneus at multiple angles. In the sedentary group, prolonged bedrest resulted in a small decrease in bone elasticity, most notable in the more responsive trabecular bone (2.5%, 2779±140, 2709±92 m/s, p=0.06). KMgCit increased trabecular elasticity (4.2%, 2705±125, 2814±140 m/s, p<0.05), while exercise showed a similar trend (3.5%, 2701±121, 2798 ±100 m/s, p=0.08). Treatment with both exercise and KMgCit demonstrated a 1.9% increase, but included only 4 subjects. These findings suggest that KMgCit and exercise training are effective countermeasures against trabecular bone quality loss during prolonged periods in microgravity. Supported by NSBRI.
Changes in muscle volume and strength following prolonged bed rest
Authors: Heinicke Katja , Wyrick Phil , Krainski Felix , Hastings Jeffrey L. , Pacini Eric , Palmer Dean , Haller Ronald G. , Levine Benjamin D.
Published: June 2021

PURPOSE

To determine the effectiveness of dynamic and resistance exercise training in attenuating the loss of structure and functional capacity of skeletal muscle during bed rest.

METHODS: Muscle volume and peak torque (Pk T) were assessed before (Pre) and following 5 weeks of −6° head down tilt bed rest in 5 (exercise) and 3 (sedentary group) healthy subjects. Training consisted of rowing (6x/wk) and resistance (2x/wk) training. The sedentary group did no training. Each subject underwent MRI (1.5T) quantification of segmental volumes of 15 contiguous 0.6 cm thick transaxial images of calf and thigh muscles. Peak isokinetic torque during ankle plantar/dorsiflexion and knee extension/flexion was determined. Correlation coefficients for muscle volume and Pk T were determined for leg anti‐gravity muscles.

RESULTS: Calf muscle volume decreased slightly by 4% while Pk T increased 31% Pre to Post in the exercise group. In sedentary corresponding values were −15% and −20%. Thigh muscle volume decreased 4% while Pk T decreased 5% Pre to Post in the exercise group. In sedentary corresponding values were −7% and −10%.

CONCLUSION: The loss of calf and thigh muscle volume was attenuated but could not be completely eliminated by exercise training during 5 weeks of bed rest. However, muscle function was well preserved with no clinically relevant loss of strength in anti‐gravity muscles.

Supported by NASA grant CA00701.
Cardiovascular mechanisms are maintained by intermittent artificial gravity exposure during bed rest deconditioning
Authors: Meng Martha , Stenger Michael , Platts Steven , Feiveson Al , Natapoff Alan , Knapp Charles , Evans Joyce , Paloski William
Published: June 2021

Successful countermeasures to adverse cardiovascular effects of spaceflight have not yet been developed. In this study cardiovascular parameters were measured at rest and in response to 30 minutes of 80° head up tilt (HUT) in two groups of men before, during and after 21 days of 6° head down bed rest (BR). 8 men received a daily, one hour dose (2.5 Gz at the foot decreasing to 1.0 Gz at the heart) of artificial gravity (AG), while 7 underwent no countermeasure. After 21 days of BR, AG‐treated subjects demonstrated greater orthostatic tolerance than control subjects (p = .012). Cardiovascular variables responsible for maintaining tolerance in AG treated subjects included an enhanced ability to increase heart rate (HR) and low frequency spectral power of blood pressure as well as to maintain stroke volume (SV) during tilt. Additionally, AG treated subjects demonstrated a more rapid return to pre‐BR responses to HUT than did control subjects by minimizing tilt‐induced increases of HR (p = .04) and decreases of SV (p = .05). Variables recorded during BR days are being analyzed to develop a model to predict orthostatic tolerance upon returning to gravity. Our data support the hypothesis that AG treatment lessens cardiovascular deconditioning in bed rested men by improving both cardiac and peripheral function and should be pursued as a space flight countermeasure. Supported by The NASA AG‐Bed Rest Project and KY NASA EPSCoR WKU52611.
PGC‐1[alpha] and upstream regulators in human skeletal muscle
Authors: Norrbom Jessica , Rundqvist Helene , Sundberg Carl Johan , Jansson Eva , Gustafsson Thomas
Published: June 2021

A central component in skeletal muscle remodelling to regular exercise is a higher mitochondrial density. The co‐activator PGC‐1α has been described as a central player in mitochondrial biogenesis and several signaling pathways have been shown to influence PGC‐1α transcription such as calcineurin, MAPK p38 and AMPK in various experimental settings.

The aim of the present study was to evaluate the importance of the above‐mentioned pathways and their effect on exercise‐induced PGC‐1α transcription. Skeletal muscle biopsies were obtained from the vastus lateralis muscle from 12 healthy males before, directly after and 2 h after 45 min one‐legged knee extension exercise. One leg exercised with restricted blood flow (R‐leg), the other with non‐restricted blood flow (NR‐leg).

Results & Conclusion: PGC‐1α mRNA expression increased significantly 2 h after exercise in the R‐leg, but not in the NR‐leg. The p38 phosphorylation and MCIP‐1 mRNA (a marker of calcineurin activation) increased following exercise regardless of blood flow condition. For pAMPK there was an increased activation in the R‐leg, which could be a possible explanation for the differential regulation of PGC‐1α.
Twelve weeks of endurance training increases mitochondrial density and percent IMCL touching mitochondria and alters IMCL storage distribution
Authors: Devries Michaela C. , Hamadeh Mazen J. , McCready Colin , Sischek Stephanie , Tarnopolsky Mark A.
Published: June 2021

Intramyocellular lipids (IMCL) are elevated in obesity and are correlated with insulin resistance (IR); however, elite athletes have elevated IMCL but are highly insulin sensitive. We postulate that the IMCL‐mitochondria physical relationship delineates whether IMCL are metabolically active.

Methods:

Muscle biopsies from 24 women (12 lean; 12 obese) were analyzed for IMCL and mitochondria ultrastructure using electron microscopy prior to and following a 12‐week progressive endurance training protocol.

Results:

In obese women, there was a strong trend for higher IMCL area density in the intermyofibrillar (IMF) region (P = 0.053) vs. lean. Training increased IMF IMCL size (P = 0.008), total fiber mitochondrial size (P = 0.006 and number (P = 0.009), subsarcolemmal (SS) (P = 0.01) and total fiber (P < 0.0001) mitochondrial area density, and the % IMCL touching mitochondria in the SS (P = 0.04), IMF (P < 0.0001) and total fiber (P < 0.0001), whereas it decreased SS #IMCL/area (P = 0.001). Following training, IMCL area density decreased in SS (P = 0.009), increased in IMF (P = 0.07), and did not change in the total fiber. HOMA‐IR was higher in obese women (P = 0.002), with no training effect.

Discussion: The increase in IMCL‐mitochondrial proximity and mitochondrial density suggests an increased capacity to utilize IMCL following endurance training. Training‐induced IMCL mobilization from SS into IMF may be more favorable, as SS IMCL could prevent signal transduction and GLUT‐4 mediated glucose uptake. (Supported by CIHR).
Exercise‐induced hypoxia in rat skeletal muscle and tendon
Authors: Skovgaard Dorthe , Kjaer Andreas , El‐Ali Henrik , Kjaer Michael
Published: June 2021

Studies have shown that intracellular oxygen in skeletal muscle decrease substantially during exercise, however less is known about the oxygenation of cells in the force‐transmitting tendons. The purpose of the present study was to test if Positron Emission Tomography (PET) with the hypoxia‐selective tracer 64CuATSM can be applied for assessment of exercise‐induced hypoxia in rat skeletal muscle and tendon. Eight rats performed one‐leg contractions of the calf muscle by electro‐stimulation of the sciatic nerve. After ten minutes of muscle contractions 21.9±1.3 MBq 64CuATSM was injected and contractions were continued for 20 minutes. Animals were scanned in a small animal PET/CT scanner and Standardized Uptake Values (SUVs) of 64CuATSM in triceps surae muscle and Achilles tendons were obtained. Compared to resting conditions the uptake of 64CuATSM was significantly increased in muscle ~1.5‐fold and in tendon ~1.3‐fold both immediately after cessation of contractions and 90 minutes post contractions (p< 0.05). The study shows that 64CuATSM is irreversible trapped in hypoxic cells and can be used as a marker of transient exercise‐induced hypoxia in skeletal muscle and loaded tendons. Furthermore the study supports a decreased intracellular oxygen level in both skeletal muscle and the force‐transmitting tendon during muscle contractions.
Ibuprofen and acetaminophen promote muscle hypertrophy and strength gains during resistance exercise in the elderly
Authors: Carroll Chad C , Dickinson Jared M , LeMoine Jennifer K , Haus Jacob M , Weinheimer Eileen M , Hollon Christopher J , Trappe Todd A
Published: June 2021

This study examined the influence of chronic consumption of ibuprofen or acetaminophen during 12 weeks of knee‐extensor resistance training (3d/wk, 70% 1RM) in the elderly. Thirty‐six individuals were randomly assigned to one of three groups and consumed the drugs in double‐blind placebo‐controlled fashion: Placebo (67±2 y; 8M, 4F), Ibuprofen (64±1 y; 9M, 4F; 1.2g/d), or Acetaminophen (64±1 y; 7M, 4F; 4g/d). Resistance training alone (Placebo) increased (p<0.05) quadriceps muscle volume (M only: 8±2%; M+F: 9±1%) and muscle strength (M only: 20±3%; M+F: 23±2%). Compared to Placebo, muscle volume increases were greater in the Ibuprofen (M only: 11±2%, p<0.05; M+F: 11±2%, p=0.06) and Acetaminophen (M only: 13±1%, p<0.05; M+F: 13±1%, p=0.06) groups. Muscle strength increases were also greater than Placebo in the Ibuprofen (M only: 29±4%, p<0.05; M+F: 30±3%, p=0.06) and Acetaminophen (M only: 26±3%, p<0.05; M+F: 28±3%, p=0.06) groups. These results suggest that chronic consumption of ibuprofen or acetaminophen during resistance training induces intramuscular changes that enhance the metabolic response to resistance exercise, which promotes additional muscle hypertrophy and strength gains during resistance training in the elderly.

NIH R01 AG020532 (TT), APS Postdoctoral Initiative Award (CC)
Moderate exercise training reduces kidney oxidative stress and mortality of hypertensive diabetic rats
Authors: Cunha Tatiana Sousa , Mendes Roberta Hack , Bertagnolli Mariane , Viegas Vinícius , Mostarda Cristiano Teixeira , De Angelis Kátia , Marcondes Fernanda Klein , Belló‐Klein Adriane , Irigoyen Maria Claudia
Published: June 2021

Hypertension plays a negative role on the development of diabetic nephropathy, increasing the mortality of patients. Moderate exercise training decreases oxidative stress and is a therapy for cardiovascular and metabolic diseases. The aim was to determine the effect of exercise on renal oxidative stress and mortality of spontaneous hypertensive diabetic rats (SHR + streptozotocin 50mg/Kg; 3 months old) randomized into: sedentary (S, n=8) and trained (T, n=8) groups. After moderate exercise training (treadmill ‐ 1h/day, 5days/wk, 10wk), kidney was excised for measurement of oxidative damage (lipoperoxidation–LPO) and antioxidant enzymes activity (superoxide dismutase–SOD, catalase–CAT, and glutathione peroxidase–GPX activity) (Student's t‐test; Kaplan‐Meier method). T group presented lower renal LPO (T=1199± 184; S=2549± 111 counts/second/mg protein), higher renal antioxidant enzymes activity (SOD:T=10.6± 0.7; S=8.3± 0.4 U/mg protein; CAT:T=23722; S=164± 17 pmol/mg protein; GPX:T=7.8± 0.3; S=6.4± 0.5 nmol/min/mg protein; p<0.05) and lower mortality (p=0.03). Our results show that moderate exercise training reduces oxidative stress and suggests that this adaptation may decrease mortality of hypertensive diabetic animals. Financial Support: FAPESP, CNPq.
Response of prostaglandins and nutritive blood flow to 7 days of exercise training in young and aged human skeletal muscle
Authors: Choi Myung Dong , Carrithers JA , Gavin TP , Kraus RM , Evans CA , Ruster RS , Knapp DJ , McCartney JS , Garry JP , Hickner RC
Published: June 2021

The purpose of this study was to determine if prostaglandins regulate alterations in muscle nutritive blood flow response to short‐term exercise training in young and aged individuals. Local thigh muscle nutritive flow and 6‐keto‐prostaglandin F1α (PGF1α) were monitored using microdialysis. Dialysate samples were collected continuously during acute exercise before and after 7 days of exercise training from 27 healthy subjects (6 young men (YM), 8 young women (YW), 7 aged men (AM), and 6 aged women (AW)). The exercise regimen consisted of 7 consecutive days of training for 1hr/day at 70% VO2peak. PGF1α content was higher during exercise after, compared to before, training in YM (43.6 ± 1.9 vs. 36.4 ± 1.3 pg/ml, respectively; P<.05) without a significant difference in nutritive flow. PGF1α content and nutritive flow during exercise was not changed in response to exercise training in YW, AW, and AM. There was a higher PGF1α content during exercise in YM than in YW and AM after training (43.6 ± 1.9 vs. 35.7 ± 1.1 and 33.6 ± 0.7 pg/ml, respectively; P<.05), but there were no differences in nutritive flow between these groups. These data demonstrate that PGF1α response to acute exercise increases with training in YM, and suggest changes in exercise‐induced PGF1α with training may not result in training‐induced alterations in muscle nutritive blood flow response to acute exercise.

NIH AG‐19209 (Hickner); MD Choi supported by EAS
PGC‐1α is required for exercise‐induced mitochondrial biogenesis, but not fiber type transformation, in skeletal muscle
Authors: Geng Tuoyu , Li Ping , Spiegelman Bruce M. , Yan Zhen
Published: June 2021

Endurance exercise training promotes mitochondrial biogenesis and fiber type transformation in skeletal muscle. Accumulating evidence suggests that peroxisome proliferator‐activated receptor γ coactivator‐1α (PGC‐1α) play a pivotal role since endurance exercise induces PGC‐1α expression, overexpression of PGC‐1α in skeletal muscle results in enhanced mitochondrial biogenesis and increased oxidative myofibers, whereas genetic disruption of the Pgc‐1α gene results in opposite changes. However, it has not been shown that PGC‐1α is required for exercise‐induced skeletal muscle adaptation, and its precise functional role is not clear. Here, mice with skeletal muscle‐specific knockout of the Pgc‐1α gene showed attenuated cytochrome oxidase IV (COX IV) and cytochrome c (Cyt c) expression, but normal induction of myoglobin expression and type IIb‐to‐IIa fiber type transformation, in response to voluntary running exercise. These findings genetically separated the functional role of PGC‐1α in exercise‐induced mitochondrial biogenesis from that in fiber type transformation.
The Radiosensitivity of Satellite Cells: Cell Cycle Regulation and Apoptosis
Authors: Caiozzo Vincent J , Giedzinski Erich , Baker Mike , Limoli Charlie
Published: June 2021

From a clinical perspective, skeletal muscles and their resident myogenic stem cells (i.e., satellite cells) are commonly exposed to significant doses of radiation. To ascertain whether irradiation inhibits satellite cell cycle progression, cells were given 5 Gy and assessed for DNA content using standard FACS methodologies. Soon after irradiation (6 hrs) satellite cells showed a marked increase (2.5‐fold) in cells at the G2/M border, the fraction of cells with a 2n complement of DNA remained high over the course of the experiment (48h). The increase in G2/M cells comes at the expense of replicating cells, as 5 Gy led to a steady decline in S‐phase cells over the first 18h following irradiation. The fraction of S‐phase cells did not recover over the subsequent 30h. As cells gradually escaped the initial block at G2/M they traversed into the block at G1/S by 12h where they accumulated at ~1.3‐fold higher levels. Poly(ADP‐ribose)polymerases (PARP) cleavage assays were used to determine if irradiated satellite cells undergo apoptosis. Apoptosis was generally increased and found to be dose‐responsive, with a relative peak occurring at 48h where apoptosis was elevated by ~1.7 fold over controls set to unity. Collectively, these data demonstrate that satellite cells are sensitive to clinically relevant doses of radiation. Further studies are needed to determine how this impacts the growth of skeletal muscle.

This work was supported by NIH grant HD050837 to establish the National Skeletal Muscle Research Center (NSMRC) at the University of California, San Diego