bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiovascular and skeletal muscle sympathetic nerve activity correlates in the embryonic chicken (Gallus domesticus) (879.6)
Authors: Onyemaechi Clinton , Crossley Dane , Hedrick Michael
Published: June 2021

The embryonic chicken (Galls domesticus) is a classic model for quantifying changes in cardiovascular form and function. Alterations in blood pressure, heart rate and blood flow have been quantified at multiple points of the 21 day incubation period. In addition, several regulatory systems have been assessed using pharmacological manipulation of receptors. However, the integration of cardiovascular function, and the capacity for central nervous system regulation of the cardiovascular system, has not been extensively investigated for non‐mammalian vertebrates. We investigated the correlation between muscular sympathetic nervous activity (mSNA) and fluctuations in arterial pressure and heart rate of the embryonic chicken. On day 18 of incubation, embryos were surgically instrumented with bipolar silver electrodes placed around the peroneal nerve to measure mSNA. On the following day a pressure catheter was inserted into a tertiary chorioallantoic artery to monitor arterial pressure and heart rate. The embryonic cardiovascular responses to pharmacologically‐induced vasodilation and vasoconstriction were investigated with sodium nitroprusside (SNP) and phenylephrine (Phe), respectively. In recovered embryos, acute spontaneous reductions in arterial pressure were associated with an increase in mSNA activity. In contrast, not all changes in arterial pressure induced by SNP or Phe were inversely related to mSNA. The lack of a consistent correlation between mSNA and arterial pressure suggests that the sympathetic regulatory capacity in embryonic day 19 chickens is relatively undeveloped compared with the adult animal.

Grant Funding Source: Supported by NSF CAREER award to DAC.
Anti‐aging gene klotho deficiency causes arterial stiffness via activation of aldosterone receptors and increased autophagy (880.6)
Authors: Chen Kai , Zhou Xiaoli , Sun Zhongjie
Published: June 2021

Background & Objective. The prevalence of arterial stiffness increases with age while the klotho level decreases with age. Klotho deficiency increases circulating aldosterone levels. The objective of this study was to test the hypothesis that klotho deficiency causes arterial stiffness via activation of aldosterone receptors.

Methods & Results. Klotho heterozygous (klotho+/‐) mice (1.5 years) and their wild type (WT) littermates were treated with or without aldosterone receptor blocker eplerenone (6 mg/kg/day, IP) for 3 weeks. Pulse wave velocity (PWV), a direct measure of arterial stiffness, was significantly increased in klotho+/‐ mice, suggesting that klotho deficiency causes arterial stiffening. Eplerenone abolished klotho deficiency‐induced arterial stiffening. Arterial stiffness was associated with increased collagen and decreased elastin contents in the media of aortas. Mechanistically, klotho deficiency increased arterial MMP2, MMP9 and TGFβ expression, which were blocked by eplerenone. In addition, klotho deficiency induced arterial autophagy and increased scleraxis (a transcription factor for collagen synthesis) expression, which was reversed by eplerenone.

Conclusion. Klotho deficiency causes arterial stiffening via activation of aldosterone receptors which leads to upregulation of MMP2, MMP9, TGFβ, and scleraxis and increased autophagy.

Grant Funding Source: Supported by HL105302 and HL 102074.
Aging, cellular senescence and disease: the influence of diet and exercise (880.7)
Authors: White Thomas , Evans Glenda , Verzosa Grace , Pirtskhalava Tamara , Tchkonia Tamara , Miller Jordan , Kirkland James , LeBrasseur Nathan
Published: June 2021

Nutrient excess and physical inactivity are primary drivers of numerous age‐related chronic diseases. A growing body of evidence has implicated cellular senescence, a process in which cells lose the ability to divide and concurrently damage neighboring cells by the factors they secrete, as an underlying mechanism of aging and its associated conditions. However, the impact of lifestyle choices on the age‐associated accumulation of senescent cells remains poorly understood. Thus, we examined the effects of a fast food diet (FFD) and a voluntary exercise intervention on multiple parameters of healthspan and cellular senescence using a transgenic mouse model that expresses green fluorescent protein (GFP) in p16Ink4a‐positive senescent cells. As expected, 12‐month old male mice that had received the FFD diet for 5 months demonstrated significantly greater gains in body weight and fat mass compared to mice fed a standard chow diet. Moreover, mice fed the FFD exhibited hyperinsulinemia, impaired glucose tolerance, reduced exercise capacity, and diastolic dysfunction. Impressively, providing an exercise wheel (26.9 ± 6.9 km/wk) in parallel with the FFD nullified the deleterious effects of the FFD on body weight and composition, whole‐body metabolism, physical performance and cardiac function. Strikingly, our data further suggest that exercise markedly lowers the number of cells in visceral fat depots that express GFP and stain positively for senescent‐associated β‐galactosidase; markers of senescence, that are highly abundant in sedentary mice fed the FFD. Correspondingly, FFD‐induced expression of senescence‐associated inflammatory factors was also diminished by the exercise intervention. Collectively, our data suggest that lifestyle choices may affect the abundance of senescence cells with advancing age, and exercise may partly mediate its salutary effects on multiple organ systems by preventing their accumulation and/or mediating their removal.
MMP‐9 deletion improves vascular permeability and angiogenesis in aging mice (880.8)
Authors: Yabluchanskiy Andriy , Ma Yonggang , Chiao Ying Ann , Voorhees Andrew , Han Hai‐Chao , Jin Yufang , Lindsey Merry
Published: June 2021

Aging is a major risk factor for cardiac morbidity and mortality. Increasing age associates with increased MMP‐9 expression, increased ECM degradation, and a decline in cardiac function. Previously, we demonstrated that wild type (WT) mice >18 months of age show impaired diastolic function, which was attenuated by MMP‐9 deletion. To investigate the changes that occur before cardiac dysfunction develops, we examined 6‐9 and 15‐18 month old (mo) WT and MMP‐9 null (Null) mice. All groups showed similar cardiac function by echocardiography and Doppler, indicating that functional changes in the left ventricle (LV) had not yet developed. Plasma proteomic profiling and LV tissue analysis revealed age‐associated increases of von Willibrand factor and VEGF in WT mice, which were enhanced in Null mice, suggesting that aging and MMP‐9 deletion stimulates angiogenesis. However, the number of vessels evidenced by GSL‐1 staining and protein expression was increased only in the 15‐18 mo Null LV. To evaluate vascular function, we injected WT and Null mice with FITC labeled dextran (70 kDa). The 15‐18 WT mo mice showed increased vascular permeability compared to the younger WT controls, which was significantly attenuated in Null mice. Our findings revealed that the age‐associated increase in MMP‐9 links with increased vascular permeability, which may contribute to the development of diastolic dysfunction.

Grant Funding Source: Supported by SC2 HL101430,HL095852,HHSN 268201000036C(N01‐HV‐00244),R01HL075360,HL05197,5I01BX000505
Resistance exercise heart rate recovery in youth with Prader‐Willi syndrome, nonsyndromal obese children and lean controls (881.13)
Authors: Castner Diobel , Pham Hoang , Judelson Daniel , Rubin Daniela
Published: June 2021

Prader‐Willi Syndrome (PWS) is a genetic disorder characterized by excess adiposity, low lean mass and hypotonia. Heart rate recovery (HRR), a determinant of all‐cause mortality, is slower in PWS in response to endurance exercise. This study examined how adiposity and PWS influence resistance exercise HRR. Eight PWS youth (age=11.5±3.5 y, body fat=44.1±3.9 %) and 16 nonsyndromal obese (OB: age=9.5±1.2 y, body fat=39.5±4.5 %) and 12 lean (LN: age=9.1±1.2 y, body fat=17.8±5.1 %) children completed six sets of a bench‐stepping protocol. Each set consisted of 10 steps per leg onto an adjustable platform (~20% of stature) while donning a weighted vest (~50% of lean body mass), followed by one minute of rest. HRR value (HRRV) was calculated as the difference between test termination HR and HR one minute after exercise. One‐way ANOVA showed PWS had a significantly lower HRRV (44±13 beats) compared to OB (63±20 beats; p=0.035) and LN (63±13 beats; p=0.044). Similar to previous research in submaximal endurance exercise, nonsyndromal OB and LN children recovered faster than PWS, suggesting adiposity alone did not affect resistance exercise HRR. The lower HRRV in PWS may be attributed to poor cardiovascular fitness and/or autonomic nervous system dysfunction inherent to the syndrome. Further, resistance exercise HRRVs appeared comparable to previously studied endurance exercise HRRVs in youth.

Grant Funding Source: Supported by USAMRAA Award W81XWH‐08‐1‐0025
Influence of fitness on core temperature thresholds for exercise ventilation (882.6)
Authors: Yogev Assaf , Martin Des , Walsh Michael , White Matthew
Published: June 2021

During incremental exercise from rest to exhaustion, core temperature thresholds are evident at exercise intensities greater than that at the anaerobic threshold or the onset of blood lactate accumulation. The effect of aerobic fitness on these core temperature thresholds remains poorly understood. PURPOSE: To compare oesophageal temperature (TES) thresholds for exercise ventilation (VE) between competitive, trained and untrained males during incremental exercise. HYPOTHESIS: Trained athletes will demonstrate a greater TES threshold for VE than untrained males. Methods: Seven college‐aged competitive male cyclists with a VO2MAX of 63.9 ± 3.7 mL•min‐1•kg‐1 (mean ± SD) and 7 college‐aged untrained males with a VO2MAX of 53.9 ± 3.5 mL•min‐1•kg‐1 volunteered for the study that approved by the SFU Office of Research Ethics. VE and its components were measured with a breath‐by‐breath metabolic cart and volunteers pedaled an electrically braked cycle ergometer at an ambient temperature of ~22oC. Each incremental exercise test started with a load of 60 W on the cycle ergometer that was incremented by 35 W/min until exhaustion. Core temperature thresholds from plots of ventilatory equivalents for oxygen (VE/VO2) and carbon dioxide (VE/VCO2) as a function of TES were 1.3°C greater (P<0.01) in the trained vs. the untrained group. The trained group relative to the untrained cyclists had a higher (P<0.01) anaerobic threshold as determined from plots of VE/VO2 and VE/VO2 as a function of VO2. CONCLUSION: Evidence supports the hypothesis that increased aerobic fitness results in a higher core temperature threshold for VE during incremental exercise.

Grant Funding Source: Supported by NSERC and CFI
Influence of five days of reduced daily physical activity on cardiac baroreflex sensitivity during acute hyperglycemia (884.10)
Authors: Holwerda Seth , Boyle Leryn , Credeur Daniel , Thyfault John , Fadel Paul
Published: June 2021

A sedentary lifestyle is associated with high fasting plasma glucose (i.e., insulin resistance) and decreased spontaneous cardiac baroreflex sensitivity (BRS). However, it is unknown whether a short term reduction in daily physical activity (RA) influences BRS at rest or during acute hyperglycemia. Nine recreationally active men (25 ± 2 yrs) underwent 5 days of RA by refraining from planned exercise and reducing daily steps (<5,000 steps/day). At baseline and after 5 days of RA, heart rate (ECG) and beat‐to‐beat blood pressure (BP, Finometer) were measured at rest and at 60‐ and 120‐min following an oral glucose tolerance test (OGTT). Linear regression slopes of three or more consecutive beats where systolic BP and RR interval changed in the same direction were averaged to determine overall BRS and separately for up and down sequences. Five days of RA (baseline, 12497 ± 836 vs. average RA days 1‐5, 3555 ± 280 steps, P<0.05) did not significantly influence overall BRS at rest or during the OGTT (P>0.05). However, during the OGTT, a significant reduction in BRS for up sequences (baseline, 31.6 ± 3.8 vs. 60min, 27.5 ± 3.3 vs. 120min, 22.1 ± 3.1 msec/mmHg, P<0.01) was found, whereas down sequences were unaffected (P>0.05). These preliminary findings suggest that 5 days of RA does not affect BRS at rest or during acute hyperglycemia. However, BRS to rises in BP are attenuated by acute hyperglycemia independent of short term RA.

Grant Funding Source: Supported by HL‐093167 (PJF) and 5T32AR048523‐09 (SWH).
Distinguishing differences between intrinsic aerobic capacity and age: a 1H‐NMR metabolomics approach (884.19)
Authors: Shearer Jane , Falegan Oluyemi , Hepple Russell , Hittel Dustin , Koch Lauren , Britton Steven , Vogel Hans
Published: June 2021

Differences in intrinsic aerobic capacity play a critical role in the development of perturbed metabolism, chronic disease and all‐cause mortality. Aims were to employ metabolomics to examine differences in age vs. aerobic capacity in young and old rats selectively bred for low (LCR) or high (HCR) aerobic capacity. Proton nuclear magnetic resonance spectroscopy (1H‐NMR) evaluated the metabolic profile of plasma samples obtained from fasted LCR and HCR. Multivariate statistical analysis was employed, with individual features judged based on variability R2 and predictive ability Q2 in unsupervised and supervised models built using the most significant metabolites. Taurine, pyruvate, acetone, valine, amongst others were key metabolites that contributed to distinct separation based on age (R2=0.83, Q2=0.65). In contrast, weaker predictive models were observed for LCR vs. HCR with scores of R2=0.53 and Q2=0.35 respectively. Key metabolites that decreased in HCR compared to LCR included isopropanol, o‐acetylcarnithine, sarcosine and proline. Pathway analysis highlighted changes in methionine, purine and TCA cycle intermediates. In conclusion, metabolomics analysis was a better predictor and age rather than aerobic capacity in LCR and HCR rats. This observation highlights the importance of age when attempting to isolate metabolic changes in aerobic capacity and their relation to chronic disease risk.

Grant Funding Source: Supported by the Alberta Cancer Foundation
Differential effects of endurance training and resistance training on doxorubicin‐induced skeletal muscle dysfunction (884.5)
Authors: Hydock David , Bredahl Eric , Gibson Noah , Quinn Colin , Hayward Reid
Published: June 2021

This study examined the protective effects of prior endurance training or resistance training on acute doxorubicin (DOX)‐induced skeletal muscle dysfunction. Male Sprague‐Dawley rats were endurance trained (motorized treadmill), resistance trained (raised food/water), or sedentary (normal cage activity) for 10 weeks, and following the activity treatments, animals received DOX. Skeletal muscle function was assessed ex vivo analyzing the soleus and extensor digitorum longus (EDL) to represent type I and type II muscle, respectively. DOX treatment resulted in decreased maximal twitch force in both the soleus and EDL. Endurance training provided the greatest degree of protection in the soleus whereas resistance training provided the greatest degree of protection in the EDL. The results suggest that exercise‐induced protection against DOX myotoxicity may be dependent on exercise mode and fiber type.

Grant Funding Source: David S. Hydock, PhD was supported by MRSG‐12‐179‐01‐PCSM from the American Cancer Society
Exercise‐induced mobilization of endothelial progenitor cells in patients with early metabolic syndrome: relation with endothelial dysfunction and MMP‐9 (884.7)
Authors: Rocha Natalia , Sales Allan , Penedo Leticia , Pereira Felipe , Silva Mayra , Miranda Renan , Silva Jemima , Silva Bruno , Santos Aline , Nobrega Antonio
Published: June 2021

Exercise mobilizes endothelial progenitor cells (EPCs) to peripheral blood, and this process can be regulated by matrix metalloproteinase 9 (MMP‐9). However, it is unknown if these mechanisms work properly in subjects with early metabolic syndrome (MetS). This study aimed to determine the effects of exercise on adhesion molecules, EPCs and MMP‐9 in subjects with early MetS. Fifteen subjects with early MetS (37±2yr) and nine healthy subjects (33±3yr) underwent an exercise session and a non‐exercise session, in random order. Adhesion molecules, EPCs and MMP‐9 were evaluated before and 10 minutes after the sessions. Presence of endothelial dysfunction was confirmed by brachial artery flow‐mediated dilation (FMD). At baseline, shear rate‐adjusted FMD was lower (P=0.04) and levels of sE‐selectin, sICAM‐1 and MMP‐9 were higher in subjects with MetS (P蠄0.03). No differences were found in number of EPCs between groups. After exercise, levels of sE‐selectin, sICAM‐1 and MMP‐9 were still higher in subjects with MetS (P<0.05). Subjects with MetS presented less CD34+/VEGFR2+ (P=0.02) and CD34+/CD133+/VEGFR2+ cells (P=0.02) and higher MMP‐9 activity (P<0.05) than healthy subjects. There were no differences between moments in non‐exercise session. Thus, subjects with early MetS presented impaired endothelial function at rest and altered response of EPCs to exercise that may be related to increased MMP‐9 activity.

Grant Funding Source: Supported by CNPq, CAPES, FAPERJ, FINEP
Endurance training ameliorates insulin resistance via suppressing of muscle endoplasmic reticulum stress (884.8)
Authors: Kadota Yoshihiro , Sasaki Tamae , Kitaura Yasuyuki , Shimomura Yoshiharu
Published: June 2021

It has been reported that ER stress caused by obesity triggers insulin resistance. In this study, we examined the effect of endurance training on ER stress in skeletal muscle caused by diet‐induced obesity (DIO). Male C57BL/6 mice were fed a control diet (10 kcal% fat) or a high‐fat (HF) diet (60 kcal% fat) for 12 weeks. At week 5 in the experiment, each dietary group of mice was subdivided into two groups (i.e. rest and training groups), and the training groups were loaded with endurance training using a treadmill (15 m/min, 30 min/day, 5 days/week). An oral glucose tolerance test (OGTT) was conducted at week 11 in the experiments. Plasma glucose concentration at 30 min of the OGTT and the area under the curve of the glucose concentration were higher in the rest group fed HF diet than in the rest group fed the control diet. The protein amount of Bip and phosphorylation levels of IRE1 alpha, JNK, and S307‐IRS‐1 were greater in the rest group fed HF diet than in that fed control diet. This impaired glucose tolerance caused by HF diet feeding was not observed in the trained group fed HF diet, and the plasma insulin concentration at 30 min of the OGTT was not different between rest and training groups fed HF diet. The increased ER stress signals were not observed in the training group fed HF diet. These results suggest that endurance training ameliorates insulin resistance caused by DIO via suppression of ER stress in the muscle.
Effects of maternal exercise during pregnancy on coronary artery vascular function in high fat fed swine offspring (886.2)
Authors: Blaize Nicole , Zartman Erica , Cabot Ryan , Newcomer Sean
Published: June 2021

The purpose of this study was to test the hypothesis that maternal exercise during pregnancy would enhance coronary artery endothelial function in swine offspring that were fed a high fat diet. Pubertal gilts were divided into exercise (n =8) and sedentary (n =8) groups. Pregnant gilts in the exercise group performed treadmill exercise 5 days per week. Offspring were fed a high fat diet and endothelial (bradykinin; BK) and vascular smooth muscle (sodium nitroprusside; SNP) function were measured at 4 and 8 months of age in the left anterior descending (LAD) artery using in vitro wire myography. Exercise sows had a significantly lower resting heart rate at week 15 of pregnancy compared to their sedentary counterparts (EX: 94.43 ± 4.0; SED: 107.13 ± 3.6 bpm). There were no significant differences in litter characteristics at birth (i.e., number of piglets alive and litter weight). There were no significant differences in vasorelaxation dose response or maximal response to BK or SNP from offspring of exercise or sedentary sows at 4 months of age (BK: EX: 94.35 ± 3.8; SED: 104.1 ± 7.7 % relaxation; SNP: EX: 101.45 ± 2.3; SED: 100.44 ± 3.4 % relaxation) or 8 months of age (BK: EX: 82.75 ± 8.5; SED: 93.92 ± 7.4 % relaxation; SNP: EX: 95.44 ± 2.7; SED: 96.51 ± 1.5 % relaxation) for the LAD artery. Therefore, maternal exercise during pregnancy does not significantly alter LAD artery function at 4 or 8 months of age in swine offspring fed a high fat diet.

Grant Funding Source: Supported by the American Heart Association Grant # 12FDG8540001 (S.C.N.)
Chronic hypoxia‐mediated oxidative stress downregulates the large‐conductance Ca2+‐activated K+ channel activity in uterine arteries in pregnancy (889.4)
Authors: Hu Xiang‐Qun , Zhang Lubo
Published: June 2021

Chronic hypoxia during pregnancy constitutes a major insult to maternal cardiovascular homeostasis, leading to complicated uteroplacental circulation. We recently demonstrated that long term high‐altitude hypoxia enhanced uterine arterial myogenic tone, which was mediated by the downregulation of the large‐conductance Ca2+‐activated K+ channel (BKCa) activity via enhanced oxidative stress. In the present study we tested the hypothesis that chronic hypoxia exposure directly increases generation of reactive oxygen species (ROS) in the uterine artery from pregnant sheep, which in turn suppresses BKCa channel activity in VSMCs of the vessel. Uterine arteries were isolated from near‐term (~140 days) pregnant sheep and incubated under 21% or 10.5% O2 for 48 hours at 37 °C. Exposure to chronic hypoxia significantly increased ROS levels and depressed the BKCa current density (p < 0.05). Neither ROS levels nor BKCa current density in tissues cultured in 21% O2 were altered by the antioxidant N‐acetylcysteine (NAC). However, the increased ROS level and depressed BKCa current density during exposure to chronic hypoxia were ablated by NAC. Our findings suggest a direct effect of chronic hypoxia in suppressing the function of BKCa channels in uterine arteries through increased generation of ROS, which may contribute to the increased myogenic tone of uterine arteries in response to chronic hypoxia during gestation.

Grant Funding Source: HL089012, HL110125
The antioxidant effects of thymoquinone in lipopolysaccharide‐activated BV2 murine microglia cells (89.5)
Authors: Duval Makini , Taka Equar , Mazzio Elizabeth , Soliman Karam
Published: June 2021

Activation of microglia, resident immune cells in the central nervous system (CNS), is implicated in the pathogenesis and progression of neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. They may cause a vicious self‐perpetuating neuronal degeneration cycle via excessive release of superoxide radicals in the system. We explored the effects of thymoquinone (TQ), the main active constituent of Nigella sativa seed oil, as an antioxidant agent in microglial activation. We hypothesized that the antioxidant properties of TQ are mediated in part by reducing proteins involved in oxidative stress induced by microglia activation. In this study, BV2 cells were stimulated with LPS in the presence or absence of TQ. To profile the effect of TQ on global protein expression of BV2 microglial cells, two‐dimensional (2D)‐gel electrophoresis with MALDI‐TOF/TOF (matrix‐assisted laser desorption/ionization ‐ time of flight) analysis was employed. Additionally, the effect of TQ on microglia activation was evaluated using immunocytochemistry‐ immunofluorescence (ICC‐IF). The results obtained indicate that TQ decreased the expression of 60 kDa heat shock, fatty acid binding, and CD68 [ED1] proteins in LPS stimulated BV2 cells. These findings suggest that the intervention of microglial activation process could be a promising therapeutic target in the treatment of a number of neurodegenerative conditions.

Grant Funding Source: Supported by NIH grants: NIMHD G12 MD007582 and P20 MD006738
Patterning neuronal networks on photolithographically‐defined parylene:silicon substrates (89.6)
Authors: Hughes Mark , Brennan Paul , Bunting Andrew , Murray Alan , Shipton Mike
Published: June 2021

Interfacing neurons with silicon can provide insights into neuronal coding and a basis for neuroprostheses. We aim to construct networks on parylene‐patterned SiO2, previously used to successfully pattern primary murine hippocampal cells. A key question is whether neurons will pattern in isolation, or whether they require a supporting cellular template. Both undifferentiated (UD) and differentiated (DF) Lund Human Mesencephalic (LUHMES) neurons fail to adhere, nor show morphological signs of differentiation, when cultured alone on‐chip (UD LUHMES parylene adhesion index (PAI) 0.02±0.05, silicon repulsion index (SRI) 1.0±0.01; DF LUHMES PAI 0.0±0.0,SRI 1±0.001). We therefore sought a different cell type to pre‐pattern on parylene. HEK 293 cells patterned accurately (PAI 0.46±0.2,SRI 0.98±0.01) as did a human glioma‐derived cell line (PAI 0.96±0.01,SRI 0.95±0.01). LUHMES, plated secondarily, adhered specifically to either cellular template, extending neurites to form a network. The next challenge is to control network topography. By altering the configuration of an array of parylene nodes, we have generated orthogonal networks. Hypothesizing that parylene can haptotactically guide neurites, different nodular features (teardrop shapes or short tracks) were created. Neurite directionality was not influenced by parylene shape; neurites instead connected with the nearest adjacent cell cluster.

Grant Funding Source: Wellcome Trust
Electrical stimulation enhances functional recovery after sciatic nerve injury (89.7)
Authors: Meadows Rena , McMillan Kate , Batka Richard , Brown Todd , Sengelaub Dale , Jones Kathryn
Published: June 2021

Direct injury to the sciatic nerve is a major clinical problem facing surgeons, as it leads to loss of limb function and devastation to a patient’s quality of life. Presently, no non‐surgical treatment strategies are clinically used to treat peripheral nerve injury (PNI). Recent work has shown testosterone propionate (TP) and electrical stimulation (ES) enhance functional recovery after injury to the facial nerve. Since lower limb nerve injuries following trauma comprise a significant portion of PNI, we hypothesized the combinatorial treatment of ES and TP improved axonal regeneration after injury to the sciatic nerve. We utilized several behavioral tests, such as grip strength, unforced gait analysis, and foot misplacement, to test this hypothesis. After a two week training period, animals received a crush injury to the right sciatic nerve. Following injury, animals received either no treatment or treatment with ES and/or TP. After treatment, animals were subjected to behavioral testing for 8 weeks to assess functional recovery. Results indicated ES accelerated grip strength recovery and improved several gait parameters compared to no treatment, whereas TP and ES + TP were not different from control. These data indicate location and type of nerve injury could guide strategies for clinical treatment.

Grant Funding Source: Supported by the Veterans Affairs
Contribution of hemodilution to renal hypoxia following cardiopulmonary bypass surgery (890.12)
Authors: Sgouralis Ioannis , Evans Roger , Gardiner Bruce , Layton Anita
Published: June 2021

Acute kidney injury (AKI) is a prevalent complication of surgical procedures that require cardiopulmonary bypass (CPB). We have used a mathematical model of the rat kidney to simulate renal hemodynamics during CPB and to study the pathways that can lead to AKI. The model represents vascular blood flow, glomerular filtration, and metabolically driven salt reabsorption along the nephron. Autoregulation is provided by active afferent arteriole constriction initiated by the myogenic response and tubuloglomerular feedback. The model simulates the effects of (i) reduced renal perfusion pressure, which reduces blood flow and glomerular filtration rate (GFR); (ii) hemodilution, which increases GFR; and (iii) hypothermia, which reduces sodium reabsorption and oxygen consumption. Medullary oxygenation is determined by the balance between oxygen consumption, which is increased by hemodilution but decreased due to low perfusion pressure and temperature, and medullary blood supply, which is reduced by hemodilution and the low perfusion pressure. Model simulations suggest that the rise in body temperature following the surgery increases medullary oxygen consumption and drives the kidney into a hypoxic state which may result in AKI. This research was supported in part by NIH grant DK‐89066.

Grant Funding Source: NIH DK089066
Contralateral nephrectomy‐induced improvement in renal structure and function following unilateral ischemia‐reperfusion injury is counter intuitively associated with markers of renal hypoxia (890.5)
Authors: Polichnowski Aaron , Licea‐Vargas Hector , Lan Rongpei , Picken Maria , Long Jianrui , Williamson Geoffrey , Rosenberger Christian , Griffin Karen , Venkatachalam Manjeri , Bidani Anil
Published: June 2021

Unilateral ischemia‐reperfusion injury (UIRI) leads to progressive renal atrophy and tubulointerstitial fibrosis (TIF). However, contralateral nephrectomy (CNX) 2 wks post UIRI can improve renal function and reverse TIF via poorly defined mechanisms. We examined the renal hemodynamic, structural and hypoxia signaling correlates associated with UIRI and its reversal by CNX. Two wks after 60 min UIRI or sham UIRI, BP (radiotelemetry), left RBF (Transonic) and 24 hr GFR measurements (FITC‐inulin, osmotic minipumps) were made in conscious rats and then repeated every 2‐3 days for 2 wks following CNX or sham CNX. In the presence of a contralateral uninjured kidney, RBF (ml/min) was reduced (P<0.05) in UIRI (4.1±0.4) vs. sham UIRI (9.3±0.8) kidneys. Without CNX, extensive renal atrophy, TIF, and tubule dedifferentiation, but minimal pimonidazole and HIF‐1α positivity, were present at 4 wks post UIRI. Conversely, CNX increased (P<0.05) GFR (ml/min) from 0.8±0.1 to 1.3±0.1 over 2 wks and led to sustained increases (P<0.05) in RBF (6.2±0.6 ml/min). CNX‐induced improvement in renal function was associated with renal hypertrophy, more redifferentiated tubules, less TIF and robust pimonidazole and HIF‐1α staining in UIRI kidneys. We conclude that TIF at 4 wks post UIRI without CNX is not associated with indices of hypoxia, which, unexpectedly correlated with recovery of renal function/structure and reversal of TIF following CNX.

Grant Funding Source: Supported by Veterans Administration, National Institute of Health, National Kidney Foundation of IL
Renal hypoxia due to increased oxygen metabolism is an independent pathway to nephropathy (890.6)
Authors: Friederich‐Persson Malou , Persson Patrik , Fasching Angelica , Hansell Peter , Nangaku Masaomi , Palm Fredrik
Published: June 2021

The proposed pathways for the development of nephropathy are many and likely to be complex and overlapping. Recent literature strongly supports a role of renal tissue hypoxia as a pathway to nephropathy but the evidence remains inconclusive as the role of hypoxia cannot be separated from confounding factors such as hyperglycemia, hypertension and oxidative stress. By increasing kidney oxygen consumption (QO2) using triodothyronine (T3) we aimed to investigate the role of renal hypoxia per se for the development of nephropathy.

Normoglycemic Sprague‐Dawley rats were treated with T3 (10 mg/kg bw/day) for 56 days. Thereafter, glomerular filtration rate (GFR), renal blood flow (RBF), total kidney QO2, kidney oxygen tension (pO2, Clark‐type oxygen electrodes) proteinuria, oxidative stress and histological alterations were evaluated and compared to corresponding controls.

T3 increased kidney QO2 (18±2 vs. 11±1 µmol/min/kidney, p<0.05) and decreased kidney pO2 (27±1 vs. 44±1 mmHg, p<0.05). Furthermore, T3 resulted in proteinuria (74±6 vs. 54±5 µg/min/kidney, p<0.05) and four of eight T3‐treated rats, but none of the controls, presented with focal tubulointerstitial fibrosis. GFR (1.4±0.2 vs. 1.5±0.2 ml/min), RBF (12.7±1.6 vs. 11.1±0.8 ml/min), TBARS (15±2 vs. 16±3 fmol/min/kidney) and blood glucose (4.8±0.2 vs. 5.1±0.2 mM) were unaffected by T3. The detected mitochondrial uncoupling and increased ATP synthesis provide a mechanistic explanation for the increased kidney QO2.

In conclusion, the present study adds further evidence in support of renal tissue hypoxia as an independent pathway to nephropathy.
Increased renal oxygen consumption leads to hypoxia in sepsis‐associated acute kidney injury (890.9)
Authors: Singh Prabhleen , Ayoyama Koji , Nourbakhsh Noureddin , Thomas Joanna
Published: June 2021

We have shown in subtotal nephrectomy (STN), a model of chronic kidney disease, there is increased oxygen consumption (QO2) factored for tubular Na reabsorption (TNa) leading to hypoxia. To demonstrate the universality of hypoxia in the pathogenesis of kidney disease, we have now examined renal oxygenation (oxygen delivery and consumption), mitochondrial function and tubular transport in acute kidney injury (AKI) due to sepsis in a rat model of cecal ligation and puncture (CLP). Data presented as mean±sem.

At 6 and 24 hours, GFR was significantly lower in CLP (2.5±0.4 vs. 3.6±0.2 ml/min and 1.2±0.3 vs. 3.3±0.2 ml/min, p<0.001). While RBF and O2 delivery was largely unchanged, renal O2 extraction and QO2 factored for GFR was higher compared to shams, (0.023±0.002 vs. 0.01±0.001 vol%ml/min and 0.11±0.01 vs. 0.05±0.01 ml/min,p<0.04). HIF‐1a expression was upregulated in the CLP kidneys at both 6 and 24 hours. In CLP, we found elevated rates of mitochondrial QO2 (199.9 ± 31.6 pMol/min vs. 163.2 ± 28.81 pMol/min, p<0.05), but significantly lower ATP generation with reduced expression of complex Va and complex III (p<0.05 for both). Proteins regulating mitochondrial morphology were also altered with increased expression of fission protein DRP1 (P<.0004) and decreased expression of PGC‐1alpha, a factor in mitochondrial biogenesis (2.2‐fold lower) in CLP. HIF‐1α activation by DMOG improved GFR at both time points.

We demonstrate increased renal QO2 despite lower GFR leading to hypoxia and dissociation between excess QO2 and ATP generation in CLP mitochondria. We are investigating alterations in mitochondrial dynamics which could explain mitochondrial dysfunction and tubular injury, and the role of HIF‐1α pathway in this. In conclusion, our data in both acute and chronic kidney injury model demonstrates early hypoxia due to increased oxygen consumption leading to oxygen demand‐supply mismatch and strongly supports the role of hypoxia as a unifying mechanism for kidney disease.

Grant Funding Source: NIH
Mathematical model of ammonia handling in the rat renal medulla (891.3)
Authors: Noiret Lorette , Thomas S. Randall
Published: June 2021

Ammonia produced in the kidney can be absorbed into the renal vein or excreted in urine. We developed a mathematical model of the rat renal medulla in order to identify some of the components controlling the fate of renal ammonia. The model simulates the movements of water, sodium, urea, NH3, NH4+ and a non‐reabsorbable solute along nephrons and vasa recta of various lengths and includes pH, potassium concentrations, and electrical potential as imposed boundary conditions at each medullary depth. A sensitivity analysis was performed to identify the transport parameters and micro‐environmental conditions that have the greatest effect on the simulated rate of urinary ammonia excretion. Our results suggest that urinary ammonia excretion is mainly controlled by the parameters that affect ammonia delivery to the descending segment of short nephron. In particular, interstitial pH in the outer medulla seems to be critical. The model provides the first coordinated picture of renal ammonia handling.

Grant Funding Source: Supported by the EPSRC through the UCL CoMPLEX doctoral training centre (UK).
Prostaglandin E2 EP3 receptor regulates the diuretic response to hypertonic stress (892.38)
Authors: Hao Shoujin , Vio Carlos , Quiroz‐Munoz Mariana , Cespedes Carlos , Hao Hao , Ferreri Nicholas
Published: June 2021

We recently showed that activation of prostaglandin E2 (PGE2) EP3 receptors during normal sodium intake is part of a negative feedback mechanism that attenuates cyclooxygenase‐2 (COX‐2) expression in the thick ascending limb (TAL). However, the functional effects of this mechanism have not been determined. Since PGE2 exhibits natriuretic and diuretic functions, we determined the consequences of EP3 receptor manipulation and its relationship to COX‐2 expression and activity in response to hypertonic saline stress. EP3 receptor expression in the outer medulla increased about 2‐fold in Sprague‐Dawley rats given free access to 1% NaCl in the drinking water for 7 days compared with tap water; p<0.05. Ingestion of 1% NaCl also increased COX‐2 mRNA accumulation and protein expression in freshly isolated mTAL tubules, an effect that was augmented when EP3 was blocked. Urine volume increased approximately 2.5‐fold during ingestion of 1% NaCl but was reduced by ~40% on days 1‐7 in rats pretreated with a EP3 receptor agonist (sulprostone: 20 μg·kg−1·day−1) for 3 days. The decrease in urine volume was associated with a decline in COX‐2‐dependent PGE2 synthesis. In contrast, the increase in urine volume induced by 1% NaCl intake was significantly augmented after pretreatment with a selective EP3 receptor antagonist (L‐798106: 100 μg·kg−1·day−1) and was associated with an increase in PGE2 synthesis. Collectively, the data suggest that the COX‐2/PGE2 signaling pathway involving EP3 underlies the diuretic response to increased NaCl intake. The mechanism that contributes to these effects is currently under investigation.

Grant Funding Source: NIH HL34300, American Heart Association 12GRNT12060350, Fondecyt 1130741, PGB12‐2007 CARE UC‐SQM
Regulation of calcium reabsorption in the rat kidney (892.4)
Authors: Edwards Aurelie , Ramakrishnan Suresh , Houillier Pascal
Published: June 2021

We have developed a mathematical model of calcium (Ca2+) transport from the thick ascending limb to the inner medullary collecting duct (IMCD) to investigate the factors that promote hypercalciuria, one of the main risk factors for kidney stone formation. Calcium is reabsorbed passively in the thick ascending limb, and actively in the distal convoluted (DCT) and connecting (CNT) tubules. The model represents the detailed epithelial transport of Ca2+ and other solutes in these segments; it accounts for the specific apical and basolateral transporters of each cell type. Model simulations reproduce experimentally observed variations in urinary Ca2+ excretion following treatment by furosemide or Ca2+ transporter inhibition. The model predicts complex interactions between the reabsorption of Ca2+ and that of other solutes in the nephron. Our results also suggest that the DCT and CNT barely adapt to upstream variations in Ca2+ transport. In contrast, regulation of the IMCD water permeability by calcium sensing mechanisms is predicted to significantly mitigate the effects of high Ca2+ loads in the distal nephron.

Grant Funding Source: Supported by the Agence Nationale de la Recherche (France)
Elucidating the role of a renal proximal tubule‐specific olfactory receptor (892.42)
Authors: Shepard Blythe , Cheval Lydie , Doucet Alain , Pluznick Jennifer
Published: June 2021

Olfactory receptors (ORs) are seven transmembrane domain G protein‐coupled chemosensors that detect odorants in the nose. We previously reported that OR signaling plays a role in the kidney (PNAS 2009), and to date we have identified 9 renal ORs. One of these is Olfr1393, which is widely expressed in a number of tissues, including kidney (by RT‐PCR screen). Using reverse‐transcribed RNA from microdissected renal segments, we found that Olfr1393 is exclusively expressed in the proximal tubule (PT; S1, S2 and S3). Like the majority of ORs, Olfr1393 is an orphan receptor with no known ligand. To screen for ligands, we cloned this receptor from the kidney and expressed it in HEK293T cells after optimizing conditions to allow for surface expression. We comprehensively screened over 1400 chemicals, and found that Olfr1393 detects preconstrained cyclic molecules containing either a carbonyl or alcohol group. We also found that when stably expressed in polarized MDCK cells, Olfr1393 localizes to the apical PM yet is excluded from the primary cilia. To determine the function of this receptor, we generated knockout (KO) mice. At baseline, KO mice appear to be in homeostatic balance based on plasma electrolytes, BUN, creatinine, urinalysis, and blood pressure measurements ‐ in future studies, we will challenge WT and KO mice with Olfr1393 ligands to ascertain how PT and renal function are regulated by Olfr1393.

Grant Funding Source: Supported by: NIDDK and ASN
Flow stimulated apical endocytosis in renal proximal tubule epithelia (892.6)
Authors: Raghavan Venkatesan , Rbaibi Youssef , Pastor‐Soler Nuria , Carattino Marcelo , Weisz Ora
Published: June 2021

The kidney is able to maintain solute and fluid reabsorption over a wide range of GFRs. Internalization of filtered low molecular weight proteins, vitamins, hormones, and other small molecules is mediated by the proximal tubule (PT) multiligand receptors megalin and cubilin. Microvillar bending in response to increases in GFR and the accompanying fluid shear stress (FSS) modulates PT ion transport capacity. However, whether FSS affects endocytosis in PT cells is unknown. Exposure of rat kidney slices to FSS led to a dramatically increased internalization of the megalin/cubilin ligand albumin and the fluid phase marker dextran in cortical tubules. Similar results were observed when PT cell lines were subjected to physiologically relevant levels of FSS. Flow stimulated endocytosis was initiated by 15‐30 min post induction of FSS, was clathrin‐ and dynamin‐dependent, and was rapidly reversed. FSS also caused a rapid elevation in intracellular Ca2+ levels, which was not observed in deciliated cells or upon inclusion of apyrase in the medium. Strikingly, deciliation and apyrase treatment also blocked the flow dependent increase in endocytosis. We hypothesize that changes in intracellular Ca2+ in response to flow‐dependent ciliary bending triggers the observed increase in PT apical endocytosis via a mechanism that involves extracellular ATP‐dependent calcium release from intracellular stores.

Grant Funding Source: Supported in part by the Lowe Syndrome Association
Statins increase AQP2 urinary excretion in hypercholesterolemic patients: a pleiotropic effect of statins of potential interest for patients with defects of AQP2 trafficking. (892.8)
Authors: Procino Giuseppe , Mastrofrancesco Lisa , Bonfrate Leonilde , Castorani Luigi , Milano Serena , Nicoletti Maria , Carmosino Monica , Portincasa Piero , Svelto Maria
Published: June 2021

We reported that statins treatment increases AQP2 membrane expression in both cultured renal cells and in the renal tubule of mouse, but the ultimate effect in human kidney is unknown. Here, we conducted a pilot clinical study on AQP2 membrane expression in hypercholesterolemic patients requiring statin therapy. In humans, urinary AQP2 (uAQP2) is a non‐invasive, reliable biomarker correlating with the amount of plasma membrane‐expressed AQP2.

Nineteen naïve patients with sustained hypercholesterolemia were enrolled along with 15 patients already under statin treatment for at least 1 year. We quantified the 24 h uAQP by ELISA. First, uAQP2 levels were compared in the two groups of patients. Then, time‐dependent changes of uAQP2 levels were studied at baseline, week1 and week 2 in naïve patients starting statin treatment (simvastatin 10‐20 mg/day).

uAQP2 was significantly higher in patients chronically treated with statins compared to naïve (3839±319 pmol/24 h vs. 2819±234 pmol/24 h).

Following statins treatment in naïve patients, uAQP2 shifted from 2471±358 pmol/24 h at baseline to 4443±493 pmol/24 h, at the end of the week1, and to 4003±450 pmol/24 h at the end of week2 of treatment.

We conclude that the pleiotropic effect of statins on AQP2 plasma membrane abundance is attainable in humans at pharmacological doses. This finding has considerable relevance for those pathological conditions in which AQP2 membrane trafficking is impaired as in nephrogenic diabetes insipidus.

Grant Funding Source: Telethon GGP12040/ AIFA MRAR08P011
Epinephrine stimulation of Cl‐ secretion in the Calu‐3 cell line (893.25)
Authors: Flaig Stephanie , Blazer‐Yost Bonnie
Published: June 2021

In the lung, β2‐adrenergic (β2‐AR) stimulation enhances fluid absorption thereby aiding in resolution of pulmonary edema after birth or lung injury, an effect mediated, at least in part, by stimulation of the epithelial Na+ channel. In the submucosal glands of the airways, however, the response to adrenergic stimuli is quite different with increased cAMP resulting in stimulation of ion and fluid secretion thereby facilitating mucociliary clearance. The current studies used electrophysiological techniques to characterize the effect of epinephrine on electrolyte transport of the Calu‐3 cell line, a well differentiated human bronchial cell line with the characteristics of the serous cells of submucosal glands. Interestingly epinephrine stimulated two anion secretory channels, the cystic fibrosis transmembrane conductance regulator and a Ca2+‐activated Cl‐ channel, thereby potentially altering mucociliary clearance via multiple channels. The data also indicate that the two anion channels are functionally linked. The results indicate that effects on serous cells should be considered when treating other respiratory target tissues with either short‐ or long‐term β2‐AR agonists.
Downregulation of intestinal sodium/glucose cotransporter‐1 is mediated by the short form of the leptin receptor (Ob‐Ra) (893.32)
Authors: Dominguez Rieg Jessica , Mahata Sushil , Köpsell Hermann , Rieg Timo
Published: June 2021

We have shown that intestinal SGLT1 is decreased in leptin receptor (long form; Ob‐Rb) deficient mice. To determine if SGLT1 is regulated by leptin itself, we utilized Ob‐Rb deficient mice with compensatory increased leptin levels (db/db; n=6), leptin deficient mice (ob/ob; n=5), and their controls (db/con and ob/con, n=10 and 6, respectively). Db/db and ob/ob mice were obese (46±1 vs 27±2 g and 46±1 vs 25±1 g, respectively; P<0.01) and hyperglycemic (532±24 vs 120±4 mg/dl and 315±34 vs 168±9 mg/dl, respectively; P<0.01) vs controls. While Western blot and immunofluorescence revealed decreased apical membrane expression of SGLT1 in db/db mice vs db/con (44%±10 vs 100%±8; P<0.01), ob/ob mice had no change in membrane abundance. In contrast to the long form, the short form of leptin receptor (Ob‐Ra) is fully functional in db/db mice. To determine if leptin‐mediated downregulation of SGLT1 is mediated by Ob‐Ra, db/db (n=4) and db/con (n=5) were treated with the Ob‐Ra antagonist catestatin, a 20 amino acid fragment of chromogranin A (5 µg/g bw/day). After 6 days, blood glucose levels rose higher in db/db vs db/con mice (Δ change: 232±51 vs 50±12 mg/dl; P<0.05), which corresponded to a marked increase in SGLT1 membrane abundance via immunofluorescence in both groups. In conclusion, leptin signaling mediated by Ob‐Ra suppresses intestinal SGLT1 abundance, which may prevent exacerbated hyperglycemia in db/db mice.

Grant Funding Source: Supported by P30DK079337, 5I01BX000323 and 10SDG2610034