bluuebunny/crossref_metadata_2025 huggingface dataset:
Adiponectin Modulates NF‐κB Mediated Cardioprotective Pathways after Acute High‐fat Feeding.
Authors: Haar Lauren , Luther Kristin , Rubinstein Jack , Ren Xiaoping , Jones WK
Published: June 2021

Previous studies indicate that the consumption of a high fat diet (HFD) 24h‐2wks prior to the experience of ischemic injury can decrease the size of the infarcted area (normalized to the area at risk) by as much as 70% relative to control fed (CFD) animals.This protective effect is NF‐κB dependent and has also been shown to work via an autophagic priming mechanism to confer protection. The current study will address the hypothesis that adiponectin activates NF‐κB mediated signaling that confers a high fat induced protective effect.

qRT‐PCR analysis of cardiac tissue from HFD animals indicated alterations in gene profiles associated with NF‐κB mediated carioprotection (HSP70, HIF1a, COX2). Cell experiments indicate that globular adiponectin activates NF‐kB activity (promoter luciferase‐based marker assay), and that siRNA knockdown of Adiponectin receptors reduces this activity. Serum levels of adiponectin were evaluated from high fat fed animals at cardioprotective time points, and show alterations in adiponectin and leptin levels that correspond to protective timelines. Finally, Adiponectin KO animals were HFD fed and assessed for response to ischemia/reperfusion injury. 24h HFD and CFD animals showed no change in infarct size after reversible 30m LAD occlusion. Ultimately this study provides a new hormonal target that may an upstream effecter of NF‐κB mediated protection induced by high fat diet. Better understanding this relationship will lead to the development of diet based therapeutics for cardiac pathology and new targets for the treatment of myocardial ischemic injury.
Effect of aqueous pericarp extract of Punica granatum (APPG) on the role of inhibition of advanced glycation end products in STZ induced diabetic retinopathy
Authors: Putta Swathi , Koratana Rohini , Killari Kishore , Kilari Eswar Kumar
Published: June 2021

The study was planned to investigate the effect of APPG on the role of inhibition of advanced glycation end products in streptozotocin induced diabetic retinopathy. Albino Wistar rats were induced for diabetes by streptozotocin and divided into five groups as vehicle control (group I), disease control (group II), standard gliclazide (Group III), group IV, and V received 50, 100 mg/kg of APPG respectively, for a period of 12 weeks. Blood glucose levels were estimated and Cataract progression due to hyperglycemia was monitored by slit lamp biomicroscope and fundoscope at the end of every 4 weeks, the biochemical parameters involved in the pathogenesis of cataract such as protein content, SOD, CAT, reduced glutathione (GSH), aldose reductase (AR), protein carbonyl content (PCO) and advanced glycation end products (AGE) were measured in the lens homogenate. Slit lamp observations indicated cataract due to hyperglycemia. Progression and maturation were delayed significantly with APPG treatment.Photographs of fundus shows marked thickness of retina and dilated blood vessels in diabetic rats compared to control. Gliclazide shows mild increase in retinal thickness and no dilated blood vessels. Normal thickness of fundus and blood vessels was observed with APPG treatment. The treatment with APPG exerted improvement in antioxidant enzymes as SOD, CAT, GSH and inhibiting AR levels, and inhibition of PCO and AGE levels in lens homogenate. These results suggest that the APPG is effective against STZ induced cataract and is beneficial in inhibition of formation of AGEs in the progression of diabetic retinopathy.
Geranylgeranyl Diphosphate Synthase Inhibitors Slow Tumor Growth in a Murine Model of Human Prostate Cancer Metastasis
Authors: Reilly Jacqueline , Hohl Raymond
Published: June 2021

Geranylgeranylated proteins of the isoprenoid biosynthetic pathway (IBP) have been implicated in a number of malignant cellular activities. Broad inhibitors of the IBP, including clinically relevant statins and nitrogenous bisphosphonates, reduce the risk of prostate cancer progression in humans likely through their reduction of protein geranylgeranylation. However, statins and nitrogenous bisphosphonates additionally deplete nearly all mevalonate derivatives, thus limiting protein farnesylation and cholesterol synthesis. Geranylgeraniol bisphosphonate (GGOHBP) was developed to inhibit geranylgeranyl diphosphate synthase (GGDPS), specifically reducing protein geranylgeranylation thereby elucidating the role of geranylgeranylation in prostate cancer metastasis in vivo. Tail vein injection of the luciferase‐expressing PC3 cell line into male SCID mice four days after initiating daily treatment of 1.25 mg/kg GGOHBP induced significantly (p<0.05) lower whole body tumor burden and an increase in overall survival as compared to vehicle‐treated control mice. Western blot analysis of mice tissues found a reduction in Rap1A geranylgeranylation in tumor burdened tissues of GGOHBP treated mice that was not observed in control mice or non‐tumor burdened tissues. In conclusion, pre‐treatment with the novel GGDPS inhibitor GGOHBP was sufficient to slow metastatic tumor growth in an in vivo murine model of human prostate cancer metastasis. NIH Pharmacological Sciences Training Grant T32 GM067795.
Cardiac Tissue Sensitization to the Sympathetic Nervous System in Renal Ischemia/Reperfusion induced Cardiac Hypertrophy
Authors: Panico Karine , Alvim Juliana , Carneiro‐Ramos Marcela
Published: June 2021

Objectives

Heart and kidney share functions of the conservation of homeostasis. Acute kidney injury occurs by an abrupt decline in renal function and can lead to the development of cardiac hypertrophy (CH), among other ways, by catecholamines release into circulation. This study aims to investigate possible modulation of sympathetic nervous system (SNS) in CH development through the cardiac beta‐adrenergic receptors pathway in CH‐induced ischemic renal injury model.

Methods

C57BL/6 male mice (n=88) were subjected to surgical occlusion of left renal pedicle for 60min followed for reperfusion (REP) for 12 and 15 days. Another group of animals were treated with Propranolol (10 mg/kg/day) for 5 days after occlusion. Morphological and molecular parameters were used to evaluate kidney and CH status.

Results

Renal ischemia/reperfusion was able to induce CH after 12d. The left kidney mass was reduced (p<0.05) and an increase on Vimentin and urea levels were observed (p<0.001) and (p<0.05), respectively. Beta‐adrenergic receptors increased after 12days when compared to Sham group (p<0.05). Treatment with SNS inhibitor was able to improve the reduction of the left kidney mass.

Conclusion

CH was accompanied by an increase in levels of beta‐adrenergic receptor, suggesting an increase in cardiac sensitivity to SNS.
Effect of hypoxia exposure on the recovery of skeletal muscle phenotype during regeneration
Authors: Chaillou Thomas , Koulmann Nathalie , Meunier Adélie , Chapot Rachel , Serrurier Bernard , Bigard Xavier , Beaudry Michele
Published: June 2021

Hypoxia impairs the muscle fibre‐type shift from fast‐to‐slow during post‐natal development; however, this adaptation could be a consequence of the reduced voluntary physical activity associated with hypoxia exposure rather than the result of hypoxia per se. Moreover, muscle oxidative capacity could be reduced in hypoxia, particularly when hypoxia is combined with additional stress. Here, we used a model of muscle regeneration to mimic the fast‐to‐slow fibre‐type conversion observed during post‐natal development. We hypothesised that hypoxia would impair the recovery of the myosin heavy chain (MHC) profile and oxidative capacity during muscle regeneration. To test this hypothesis, the soleus muscle of female rats was injured by notexin and allowed to recover for 3, 7, 14 and 28 days under normoxia or hypobaric hypoxia (5,500 m altitude) conditions. Ambient hypoxia did not impair the recovery of the slow MHC profile during muscle regeneration. However, hypoxia moderately decreased the oxidative capacity (assessed from the activity of citrate synthase) of intact muscle and delayed its recovery in regenerated muscle. Hypoxia transiently increased in both regenerated and intact muscles the con‐ tent of phosphorylated AMPK and Pgc‐1a mRNA, two regulators involved in mitochondrial biogenesis, while it transiently increased in intact muscle the mRNA level of the mitophagic factor BNIP3.
Prostaglandin E2 Signaling via EP4 Receptor is Important for Cell Cycle Progression and the Regulation of Reactive Oxygen Species Production in Primary Myoblast
Authors: Mo Chenglin , Wetmore Lori , Zhao Ruonan , Bonewald Lynda , Brotto Marco
Published: June 2021

Our previous data have shown that conditioned media from osteocytes and prostaglandin E2 (PGE2), a major secreted factor by osteocytes, promotes C2C12 myogenesis. PGE2 and EP4 receptor agonist CAY10598 enhance, but EP4 receptor antagonist L161,982 inhibits primary myoblast proliferation. Since the activation of other EP receptors did not show any noticeable effect, EP4 receptor may play a major role in the regulation of primary myoblast proliferation. To further study the mechanisms behind these effects of PGE2/EP4 signaling, we determined the gene expression of cell cycle regulators, such as cyclin E, p21, and myostatin, following the treatments with PGE2, CAY10598 or L161,982. Consistent with our findings in cell cycle analysis, the results indicated that PGE2 and CAY 10598 upregulate cylin E expression, but downregulate p21 and myostatin expression. In contrast, L161,982 decreases cylin E expression, but increases p21 and myostatin expression. Moreover, treatment with L161,982 significantly increased reactive oxygen species (ROS) levels by 250%. Cotreatment with antioxidant N‐acetyl cysteine or sodium ascorbate successfully reverses the inhibition of myoblast proliferation and excessive ROS production caused by L161,982. These results suggest that PGE2 signaling via EP4 receptor could regulate myogenesis by promoting myoblast proliferation via a ROS‐dependent modulation of cell cycle.
No Thermal Effect of GSM Electromagnetic Waves Exposure on Slow‐Type Skeletal Muscles in Female Rats
Authors: Ramadan Wiam , Darwich Walaa , El‐Dirani Zeinab , Khachfe Hassan , Moustafa ElSayed Mohammed , Estève Eric , H. Joumaa Wissam
Published: June 2021

The concern from the increase of population exposure to electromagnetic fields from various sources has been addressed by the World Health Organization and other international organizations and institutions. The study of the effect of GSM‐signals on mammalian skeletal muscle is encouraging because muscles are extremely plastic and are capable of modifying their structure in coordination with the activity they develop. Our results show that 6 weeks of continuous exposure to GSM electromagnetic waves (900 MHz, Eeff= 25V/m) for 24 hours a day induce an increase by 15% in muscle mass. Such an increase in muscle mass observed could be related to modification in water content and/or in the proteins synthesis. In fact, 6 weeks of continuous electromagnetic waves exposure induces an increase by 42% and 32% in percentage of water content and were observed respectively. Moreover, no significant effect was observed in total testosterone level after GSM wave's exposure period (control: 2.01 ± 0.28 ng/ml, Exposed: 2.12 ± 0.31 ng/ml, n=20).

These results suggest that continuous exposure to GSM relay antenna can induce a morphological modification in slow‐ type skeletal muscle of female rats which could have an effect on functional characteristics as well as Excitation‐Contraction Coupling mechanism.
Evidence for a Sliding Channel Hypothesis for Muscle Excitation‐Contraction Coupling
Authors: Pitake Saumitra , Ochs Raymond
Published: June 2021

The sarcolemma membrane DHPR of skeletal muscle and the sarcoplasmic reticular (SR) bound ryanodine receptor (RyR), are both Ca2+ channels that are known to interact in response to sarcolemmal depolarization, transmitting a movement of the DHPR, through physical contact with the RyR, to release of Ca2+ from the SR lumen to the cytosol through the RyR channel. The mechanism of this excitation‐contraction coupling (ECC) is unknown. We propose the Sliding Channel Hypothesis, in which the DHPR blocks its closely apposed RyR, and moves, under the influence of the electric field imposed by cell depolarization to block a formerly unoccupied RyR, with release of Ca2+ from the just‐freed RyR. Supporting this hypothesis, we found that ryanodine, the selective inhibitor of the RyR, blocked depolarizationinduced calcium entry through L‐channel (measured by whole‐cell patch clamp). Yet, store‐operated calcium entry (SOCE) was little affected by ryanodine. Furthermore, measurements of cytosolic Ca2+ by FURA2 fluorescence showed that underconditions of movement of the DHPR – K depolarization or the DHPR agonist BayK – there was an enhanced sensitivity to ryanodine. This suggests a movement of the two channels to enable increased ryanodine binding to the RyR. Under conditions that also increased cytosolic Ca2+ but did should not induce a relative movement of the channels – added extracellular Ca2+ or the RyR channel activator methylcresol – there was no change in ryanodine sensitivity. We also propose that the entry of Ca2+ for the two processes is distinct: directly into the cytosol for ECC, but directly into the SR lumen for CCE.
Polymerase Gamma Mutator (PolG) Mice Rely on Increased Glycolytic Flux for Energy Production
Authors: Saleem Ayesha , Safdar Adeel , Kitaoka Yu , Akhtar Mahmood , Marquez Olivia , Tarnopolsky Mark
Published: June 2021

PolG mice have reduced mitochondrial oxidative capacity secondary to systemic mitochondrial dysfunction, and subsequently show exercise intolerance. While the deleterious effects on oxidative capacity in the PolG mice have been clearly documented, assessment of a compensatory increase in anaerobic capacity in PolG mice is lacking. Thus, we sought to delineate the extent of glycolysis/gluconeogensis as a means of energy production in the PolG mice. PolG and wild‐type (WT) littermates were sacrificed at 10 mths of age, and blood/tissues were harvested. Primary dermal fibroblasts were also isolated from the animals and used to measure basal/maximal glycolysis using the Glycolysis stress test (Seahorse Bioscience). PolG mice displayed higher respiratory exchange ratio (RER) values, coupled with 55% lower locomotor activity compared to littermate WT mice (P < 0.05). PolG mice displayed resting hypoglycemia (3.4 mM), concomitantly with lower glucose levels throughout the GTT test as compared to WT, ~3‐fold higher PFK content, and elevated plasma lactate levels (>10 mM)(all P < 0.05). In vitro experiments provide further proof that PolG derived dermal fibroblasts have an ~50% higher basal and maximal rate of glycolysis vs. WT control. It is likely that the higher lactate content serves as substrate for the Cori cycle to generate glucose in the liver via gluconeogenesis. Indeed the mRNA content of two important gluconeogenic liver enzymes, G6P and PEPCK, was increased by ~3‐4x fold in the POLG mice compared to WT. Lactic acidosis and hypoglycemia have been associated with poor prognosis in a variety of mitochondrial diseases, and the presence in the PolG animals is a novel finding that warrants further attention. Funded by CIHR.
Dynamic Proteomic Responses to Skeletal Muscle Damage and Repair in Mice
Authors: Kramer Fritz , Stimpson Stephen , Shearer Todd , Billin Andrew , Russell Alan , Hellerstein Marc , Turner Scott , Evans William , Shankaran Mahalakshmi
Published: June 2021

Skeletal muscle is an innately plastic organ that responds to damage in an organized and highly conserved manner. We measured turnover rates across the skeletal muscle proteome following physiological muscle injury and repair in young male mice. Animals were challenged by a bout of 60 unilateral eccentric contractions during which hind limb plantarflexor muscles were forcibly lengthened while being concomitantly stimulated to contract. This induced an immediate 30% isometric force deficit 24‐hrs after injury, with functional restoration in 4 weeks. To determine whether changes in protein kinetics accompanied alterations in limb function, we labeled mice with D2O at varying time points post‐injury (day 0‐1, 1‐3, 3‐7, 8‐13 and 2‐12), and performed high‐resolution LC/MS/MS of muscle digests to measure fractional synthetic rates (FSR) of hundreds of proteins. Protein kinetics revealed distinct time‐dependent signatures in muscle in response to eccentric damage. With the notable exceptions of desmin and a few other proteins, FSRs of many myofibrillar and extracellular matrix (ECM) proteins were significantly decreased at both 0‐1 and 1‐3 days after injury. In contrast, FSR of myofibrillar and ECM proteins were significantly increased after day 3, indicating enhanced remodeling of the contractile apparatus. Similar changes were seen in many mitochondrial and cytosolic proteins in the repair phase. In conclusion, dynamic proteomics represents a powerful technique to explore temporal responses to skeletal muscle damage and recovery in mice, with potential for development of robust biological and PD markers of repair in clinical settings.
A novel mechanism of ERK1/2 regulation in smooth muscle involving acetylation of the ERK1/2 scaffold IQGAP1
Authors: Vetterkind Susanne , Lin Qian Qian , Morgan Kathleen
Published: June 2021

Objectives

Ceramide, a second messenger associated with cardiovascular disease, is known to activate extracellular signal regulated kinases 1 and 2 (ERK1/2). Here, we determined that the effect of ceramide on ERK1/2 is mediated by a scaffold protein.

Methods

Experiments were performed with A7r5 smooth muscle cells using western blot analysis.

Results

We show that the ERK1/2 scaffold IQGAP1 is cleaved in response to ERK1/2 activation. IQGAP1 cleavage is prevented in the presence of C6 ceramide. Conversely, treatment with a ceramide inhibitor leads to increased IQGAP1 cleavage and decreased ERK1/2 activation. Analysis of the IQGAP1 amino acid sequence revealed several potential cleavage sites for proteases of the proprotein convertase family, located to produce the observed cleavage products. Moreover, these potential cleavage sites overlap with motifs for lysine acetylation. Interestingly, deacetylase inhibitor treatment increases IQGAP1 acetylation, as detected by an acetylated lysine specific antibody, and at the same time, reduces IQGAP1 cleavage.

Conclusions

Based on our data, we suggest a model in which IQGAP1 is cleaved upon ERK1/2 activation, and cleavage is regulated by acetylation of the cleavage sites. Activation of ERK1/2 by ceramide, which is known to activate acetyltransferases, appears to be mediated by acetylation‐dependent stabilization of IQGAP1. This novel mechanism could open new possibilities for therapeutic intervention in cardiovascular diseases. Funding: Dudley Allen Sargent Grant, PO1 HL086655.
Effects of ageing on sympathetically‐mediated cerebrovascular tone and autoregulation
Authors: Thompson Emma , Coney Andrew , Marshall Janice
Published: June 2021

The role of sympathetic fibres in cerebral circulation is unclear. Evidence suggests sympathetic activity exerts a tonic constrictor influence on cerebral blood flow (CBF) and protects against increases in arterial blood pressure (ABP) at the upper limit (UL) of autoregulation. Ageing impairs sympathetic functioning, but how this affects cerebral circulation is unknown.

In anaesthetised, young male Wistar rats (Y: 6‐8 weeks, n=7), we isolated and stimulated the sympathetic superior cervical ganglion (SNS) at 1‐50Hz for 5s. CBF recorded from common carotid artery after external carotid ligation, was 2.5±0.2ml/min and fell in a frequency‐dependent way to 1.1±0.2ml/min; a decrease of 58±7%. In 4 Y rats, phentolamine (10mg/kg i.v.) decreased basal ABP to near the lower limit, and CBF from 2.3±0.2 to 1.4±0.1ml/min and attenuated the response to SNS by 72±3%. In n=9 Y rats, sympathectomy increased basal CBF by 0.6±0.1ml/min. Phenylephrine was infused (0.1–200µg/kg/min i.v.) to raise ABP, and the autoregulatory UL determined by dual‐line linear regression analysis of CBF vs ABP. The UL was higher than intact Y rats (178±3* vs 168±2mmHg; P<0.05).

In old rats (O: 52‐58 weeks, n=6), basal CBF was higher than Y rats; 3.3±0.2ml/min*, but was similarly decreased by SNS (to 1.6±0.2ml/min; P=0.06 vs Y: a 51±6% decrease). Phentolamine decreased basal CBF from 3.1±0.2, to a lower level than in Y rats (1.4±0.2ml/min*), but the response to SNS was similar (77±7% decrease).

We propose that sympathetic fibres have similar capacity to induce vasoconstriction in O as Y rats and a similar proportion is mediated by α‐adrenoceptors. Further, sympathetic vasoconstriction limits the autoregulatory UL, at least in Y rats.

British Heart Foundation funding is gratefully acknowledged.
Inactivation of a Potassium Channel
Authors: McDermott Ann , Bhate Manasi , Wyle Benjamin , Xu Yunyao
Published: June 2021

Ion binding in a potassium ion channel is studied, yielding insights into inactivation. At high potassium the selectivity filter is in a conductive form, and at low potassium it collapses into a long‐lived nonconductive structure with reduced ion occupancy. Solid state NMR methods are applied to full length wild type channel in membrane bilayers, and to the inactivation‐less mutant E71A. We test the hypothesis that a universal important channel‐inactivation process has as its central step the evacuation of ions from the selectivity filter.
Hypertension in NBCe2 Deficient Mice Caused by Enhanced ENaC Activity
Authors: Wen Donghai , Yuan Yang , Warner Paige , Wang Bangchen , Cornelius Ryan , Li Huaqing , Wang Jun , Boettger Thomas , Sansom Steven
Published: June 2021

Mutations of the electrogenic Na‐HCO3 cotransporter NBCe2 are associated with hypertension but the detailed pathogenesis is not well understood. Here we showed that up‐regulation of the epithelial Na channel (ENaC) in the distal nephron plays a critical role in hypertension caused by NBCe2 deficiency in mice. Wild type (WT) and NBCe2 knock out (KO) mice were fed an acid diet (1.5% NH4Cl) for 7‐10 days. Mean arterial pressure (MAP) was measured by tail cuff before and after the treatment with amiloride (Amil, 25 mg/L in drinking water). The MAP (mmHg) was higher in KO compared with WT before treatment (KO: 124.5 ± 2.2 vs WT: 110.6 ± 4.4). After treatment, the MAP in both groups dropped to a similar level (KO: 98.4 ± 3.7 vs WT: 99.1 ± 4.4). Western blot showed that the ENaC‐α expression in the kidney cortex was higher in KO compared with WT. Metabolic cage experiments showed that urinary Na excretion increased 3‐fold after Amil treatment (5 mg/kg, ip) in KO, while increasing only 20% in WT. The urinary K excretion also decreased significantly after Amil treatment in the KO but was similar before and after treatment in WT. Micropunture experiments showed that the [K] was significantly higher in the connecting tubule (CNT) of the KO compared with WT (KO: 21.9 ± 0.6 vs WT: 17.9 ± 1.5 mM), while the transepithelial potential (Vte, mV) was significantly lower (KO: ‐3.2 ± 0.2 vs WT: ‐1.6 ± 0.2). After Amil treatment, the Vte increased to ‐0.1 ± 0.2 in KO and 0.7 ± 0.4 in WT. These results show that both the ENaC expression and activity are increased in the KO, which contribute to the hypertension caused by NBCe2 deficiency.
Feedforward Mechanisms Adjust Cerebral Blood Flow During Anticipated Postural Changes
Authors: Bourdages George , Yates Bill
Published: June 2021

Head‐up tilt can result in a decrease in venous return to the heart and a decline in cerebral perfusion. Although feedback mechanisms such as vestibulosympathetic and baroreceptor reflexes compensate for orthostatic hypotension, we postulated that feedforward mechanisms also adjust cerebral blood flow (CBF) during anticipated postural changes. To test this hypothesis, cats were instrumented to record blood flow from the carotid arteries (cerebral blood flow, CBF) and acclimated for restraint on a tilt table. We trained the animals to associate 60° head‐up tilt (HUT) with a visual cue, which was provided 10 sec before tilt onset. Within 10 days following pairing of the light cue and 60° HUT, there was a significant attenuation (p<0.05, ANOVA) in lability of CBF, which changed <5% at the onset of the tilt. After animals were well‐trained, a false cue (light cue before 20° HUT or a light cue but no tilt) was provided during 10% of trials. Such false cues did not result in a significant change in CBF. These data support the hypothesis that anticipation of movement acts to stabilize CBF and decreases the likelihood of orthostatic hypotension. However, since anticipation of movement without a postural change did not affect brain perfusion, we concluded that feedback signals can override inappropriate feedforward signals. These data suggest that feedback and feedforward signals are integrated by the nervous system to provide for homeostasis during postural alterations.
Estrogen Induces Coronary Arterial Dilation via Downregulation of Voltage‐gated, Ca2+ Channels
Authors: Niyonsaba Edouard , Moussa Mohamed , Rusch Nancy , Hill Brent
Published: June 2021

Gender studies have suggested that the female sex protects against abnormal vascular tone. Our lab has previously shown that estrogen (E2) can downregulate voltage‐gated, L‐type Ca2+ channels (VGCCs) to prevent excessive vasoconstriction. The aim of this study is to determine the mechanisms associated with this E2‐induced downregulation. The right coronary artery was obtained from hearts of female pigs. Coronary arteries were sectioned into longitudinal strips (Western blots, Real‐time PCR) or rings (isometric tension) and cultured for 24 hrs in 1nM E2 or EtOH (E2 solvent). The role of the endothelium was evaluated by removing the endothelium of the artery with a toothpick before the 24 hr incubation period. E2 decreased the protein expression of the pore‐forming α1C subunit of the VGCC by 35%, but did not affect the mRNA encoding the α1C subunit. This decrease was not affected by the presence of the endothelium. Isometric contractions were also measured to the VGCC agonist, FPL64176, in endothelial intact and denuded rings. Although E2 decreased the FPL64176 contraction by 50%, the presence of the endothelium had no effect. To determine the role of estrogen receptors (ER) the arterial strips were incubated with either an ER α/β antagonist (ICI 182,780), or a G‐protein‐coupled ER antagonist (G‐15). Using Western blots, only ICI 182,780 prevented the E2‐induced decrease in the α1C subunit expression. Overall, our results suggest that E2 posttranscriptionally downregulates VGCCs via activation of ER α/β; the downregulation is endothelium‐independent. Support: Grant #P20 GM103429‐11.
Effects of Liraglutide on Cardiac Function and Myocardial Infarct Size in the Setting of Obesity
Authors: Goodwill Adam , Mather Kieren , Noblet Jillian , Sassoon Daniel , Conteh Abass , Tune Johnathan
Published: June 2021

Glucagon like peptide‐1 (GLP‐1) based therapies have been shown to improve cardiac function and protect against myocardial ischemic injury in non‐obese animals. However, whether these therapies confer protection against ischemic damage in the setting of obesity has not been established. Obese Ossabaw swine were subjected to a gradually developing coronary occlusion by placement of an ameroid occluder on the left anterior descending coronary artery. Animals then received daily subcutaneous injections of saline or the stable GLP‐1 analogue, liraglutide (0.005‐0.015 mg/kg/day) for 30 days. Following this treatment period, animals were anesthetized and an open chest procedure was performed to assess cardiac and systemic responses to administration of the sympathomimetic compound, dobutamine (0.3‐30 μg/kg/min). Liraglutide treatment had no effect on baseline hemodynamic variables, including mean pressure (P = 0.32), stroke volume (P = 0.80), heart rate (P = 0.26), or ejection fraction (P = 0.80). Dobutamine administration dose‐dependently increased heart rate, systolic ejection pressure, dP/dtmax, stroke work, and decreased contraction time, left ventricular end diastolic volume, and stroke volume. Dobutamine‐induced changes were unaffected by liraglutide administration. Excised hearts were sliced into 1cm thick sections and stained with tetrazolium to quantify the area of myocardial infarction. Overall, total myocardial infarct size was not significantly different in between groups (P = 0.41). These findings indicate that liraglutide does not significantly affect cardiac function or myocardial infarct size in the setting of obesity.
Endothelial Kir channels amplify the actions of endothelium‐dependent vasodilators in systemic resistance arteries
Authors: Sonkusare Swapnil , Dalsgaard Thomas , Bonev Adrian , Nelson Mark
Published: June 2021

Smooth muscle cells (SMCs) in systemic resistance (mesenteric) arteries lack strong inward rectifier K+ (Kir) channels, which are responsible for external K+‐induced dilations of cerebral arteries. Here we report that pressurized, resistance‐sized (3rd‐order branches) mesenteric arteries from mice dilate to an elevation of external K+ from 6 to 14 mM, which is prevented by Kir blockers Ba2+ (100 μM) and ML 133 (20 μM) or removal of the endothelium. Freshly isolated endothelial cells (ECs) exhibited robust Kir currents (‐7 pA/pF at ‐140 mV, 60 mM external K+). Kir channel currents and K+‐induced dilations were absent in myocytes or arteries from EC‐specific Kir2.1 knockout mice. We have recently shown that muscarinic receptor activation causes vasodilation through membrane hyperpolarization via stimulation of EC TRPV4 (transient receptor potential vanilloid 4) and IK (intermediate conductance calcium activated potassium) channels (Sonkusare et al, Science, 2012; Science Signaling, 2014). We therefore tested the hypothesis that EC Kir channels act as amplifiers to this signaling pathway to enhance EC‐dependent vasodilation. Indeed, vasodilation to stimulation of each element of this pathway (muscarinic receptors, TRPV4, IK) was attenuated by EC Kir channel blockers or in the absence of EC‐Kir2.1. These results suggest that EC Kir2.1 channels have a central role in vasodilation to external K+ and endothelial‐dependent vasodilators.
Blunted Nocturnal Blood Pressure Dipping and Exaggerated Morning Blood Pressure Surge in Response to a Novel Repetitive Sleep Restriction Challenge
Authors: Yang Huan , Haack Monika , Lamanna Mackenzie , Mullington Janet
Published: June 2021

The risk for cardiovascular disease increases with attenuated nocturnal blood pressure (BP) dipping and an exaggerated morning BP surge. Sleep deprivation has been associated with increased prevalence of hypertension, however, the evidence for a relationship between insufficient sleep and BP dipping/morning surge is lacking. In a 22‐day protocol, 43 healthy participants (age 32±2 yrs; BMI 24±1 kg/m2; 21 men and 22 women) were randomly assigned to 4 cycles of repeated sleep restriction (SR); (permitted 4h of sleep/night for 3 nights followed by a recovery sleep, repeated 4 times), or a sleep control (SC) group (8h/night). Beat‐to‐beat BP was recorded during six 24h periods via Portapres: baseline (BL), experimental (3rd day of each of the 4 cycles), and recovery. Mean arterial BP (MAP) dipping was calculated as [1‐ sleep MAP/wake MAP] x 100, while morning surge was determined as difference between MAP 0.5h after and 2h before wake. Nocturnal MAP dipping (19±4% in SR and 18±2% in SC, p>0.05) and morning MAP surge (10±2mmHg in SR and 11±2mmHg in SC, p>0.05) were not different between two groups at BL. Repetitive SR significantly blunted MAP dipping compared to SC (10±2% in SR and 16±2% in SC, P=0.02). Morning MAP surge was significantly increased in SR, but decreased in SC (15±3mmHg in SR and 8±2mmHg in SC, p=0.02). Attenuated MAP dipping reached the maximum changes from BL after the 1st SR cycle, and stabilized. Increases of morning MAP surge showed a trend of continuous rising over the 4 cycles. In conclusion, repeated SR induced significant sustained attenuation of nocturnal dipping, and increased morning surge of MAP progressively through 4 cycles. Supported by NIH (HL‐106782).
Mathematical model of renal hemodynamic and structural consequences of increased proximal sodium reabsorption in early diabetic kidney disease
Authors: Hallow K Melissa
Published: June 2021

A mathematical model of integrative renal and cardiovascular function was used to evaluate the potential role of increased sodium reabsorption through sodium glucose cotransporters (SGLT) in the proximal tubule (PT) in driving hemodynamic and structural changes in the kidney in early diabetic kidney disease. First, the effect of glomerular pressure (GP) on adaptive hypertrophy of the glomerulus was modeled based on literature data from subtotal nephrectomy studies. Increased GP following nephrectomy was assumed to drive glomerular hypertrophy, increasing capillary surface area and thus the ultrafiltration coefficient (Kf). As Kf increased, GP returned to close to normal levels, and blood pressure and glomerular filtration rate (GFR) were maintained near pre‐nephrectomy levels. This effect of GP on hypertrophy was assumed to be a general adaptive mechanism, not specific to nephrectomy. Next, increased sodium reabsorption through SGLT resulting from high glucose levels in diabetes was modeled as an increase in the rate of PT sodium reabsorption. This resulted in an initial elevation in both GP and GFR through tubuloglomerular and neurohormonal feedback mechanisms. Over time, Kf increased while GP returned toward baseline. However, maximum hypertrophy occurred before GP completely normalized, indicating that SGLT‐driven PT sodium reabsorption can lead to sustained elevations in GP. This sustained increase in GP, as well as repeated spikes in glucose that elevate GP further, may cause cumulative damage to the glomerular membrane, leading to the progressive decline in GFR that follows the hyperfiltration phase in diabetic kidney disease. An interactive interface to the model is being developed and is available at qsp.engr.uga.edu:3838/CVRmod.
Effects of Endothelin‐A Receptor and Angiotensin Converting Enzyme Inhibition on the Development of Progressive Proteinuria in Diabetic Dahl SS Rats with Pre‐existing Renal Disease
Authors: Spires Denisha , Taylor Lateia , McPherson Kasi , Williams Jan
Published: June 2021

The endothelin (ET) system has recently emerged as an interesting therapeutic target for the treatment of diabetic nephropathy (DN). Recently, we observed that ETA receptor blockade prevented the progression of renal disease in diabetic Dahl salt‐sensitive (STZ‐SS) rats with pre‐existing renal disease. Since angiotensin converting enzyme inhibitors (ACEi) are the first‐line of therapy for patients with DN, the present study examined whether treatment with an ACEi (lisinopril) in combination with an ETA receptor blocker (ABT‐627) would have a more beneficial effect on the progression of renal disease in STZ‐SS than ETA receptor blockade alone. Nine week‐old SS rats were treated with streptozotocin (STZ, 50 mg/kg, i.p.) to induce diabetes. After 3 weeks of diabetes, proteinuria increased to 353±34 mg/day. The rats were then separated into three groups: (1) vehicle (drinking water) and (2) ABT‐627 (5mg/kg/day) and (3) ABT‐627+lisinopril (10mg/kg/day). After 6 weeks of treatment, MAP (via telemetry) and proteinuria decreased by 15% and 40%, respectively, in STZ‐SS rats treated with ABT‐627 alone. However, we observed a greater effect with combination therapy which produced a 20% and 70% reduction in MAP and proteinuria, respectively, in STZ‐SS rats. These results indicate that chronic ETA receptor blockade alone or in combination with an ACEi delays the development of progressive proteinuria during diabetes‐induced renal injury by primarily reducing arterial pressure.This research was supported by NIGMS NIH P20GM104357 and AHA 12SDG9440034.
Expression of Toll‐like Receptor 4 Is Augmented in the Kidney with Chronic Partial Ureteral Obstruction and Further Stimulated by Lipopolysaccharide
Authors: Ma Hongbao , Yang Yan , Kheradnam Sharon , Chou Shyan‐Yih
Published: June 2021

Urinary traction infection frequently occurs in the obstructed kidney. Toll‐like receptor 4 (TLR‐4) plays a critical role in recognizing pathogen‐associated molecular patterns and actives innate immunity by mediating production of inflammatory cytokines. In the present study we examined the expression of TLR‐4 in Sprague‐Dawley rats with partial ureteral obstruction (PUO) for 30 days. After removal of the right kidney, the left ureter was diverted into the psoas muscles to create PUO. In an additional group of PUO rats, lipopolysaccharide (LPS)(1 mg/kg BW) was administered intraperitoneally 24 hr before removal of the kidney for immunoblot and RT‐PCR analyses. Immunoblot analysis showed that TLR‐4/b‐actin in the renal cortex of 8 PUO rats was 10.1±0.7 (mean±SE)(densitometry units), significantly greater than 5.3±0.7 in the 8 sham‐operated rats, and increased significantly to 12.5±2.7 in 8 PUO rats receiving LPS. TLR‐4/b‐actin in the medulla of the PUO kidney was 9.6±1.8, significantly greater than 5.5±1.2 in the sham‐operated rats, and increased significantly to 13.1±0.9 in PUO rats receiving LPS. In the RT‐PCR analysis, TLR‐4 mRNA expression in the cortex increased significantly by 1.2±0.1(2‐exp‐DD Ct) in PUO rats when compared with sham‐operated rats and increased further by 1.4±0.3 in PUO rats receiving LPS. These results show that TLR‐4 expression is augmented in the obstructed kidney and further stimulated by LPS, suggesting an important role of TLR‐4 in the defense against urinary tract infection in obstructive uropathy.
Expression/Phosphorylation of the Renal NaCl Cotransporter (NCC) in Transplant Patients with Hypertension
Authors: Rojas‐Vega Lorena , Jimenez Aldo , Gomez‐Ocadiz Ruy , Alberú Josefina , Morales‐Buenrostro Luis , Gamba Gerardo
Published: June 2021

Tacrolimus‐induced hypertension in mice is associated with increased activity of the renal NaCl cotransporter (NCC). It is not known if this occurs in humans. Here, we performed a prospective, longitudinal and observational study to assess the prevalence of hypertension in patients undergoing renal transplantation and the expression/phosphorylation of NCC in urinary exosomes. From January 2013 all adult patients receiving a kidney allograft were enrolled. All patients received tacrolimus. At six and 12 months after surgery we assessed general clinical and laboratory variables, tacrolimus blood levels, and arterial blood pressure, which at six months was determined by ambulatory blood pressure monitoring (ABPM). At six and twelve months urinary exosomes were extracted to perform Western blot analysis using total and phospho‐NCC antibodies (T45‐50‐55‐NCC). At the moment 43 patients (69% male) have completed six months of follow up and ABPM. Mean age 36.7 ± 13.5 years. Of 17 women three had hypertension (17%), while of 26 males, 15 had hypertension (57%). Hypertensive men were older than normotensive (44.2 ± 14.2 vs. 30.7 ± 9.7, p<0.001), but body mass index, allograft rejection rate, serum tacrolimus and creatinine levels were similar. Western blot analysis has been performed in urinary exosomes from 9 hypertensive and 5 normotensive men. Values in normotensive men were taken as 1 and in hypertenvise normalized accordingly. Values in hypertensive vs. normotensive were: for NCC expression: 2.94 ± 0.5 vs. 1.0 ± 0.2 and pNCC 1.8 ± 0.4 vs. 1.0 ± 0.3, respectively (p<0.05). Our data suggest that NCC expression/phosphorylation is increased in hypertensive postranplant patients treated with tacrolimus.
Bicarbonate Therapy Alleviates Hypertension‐Induced Renal Injury In Dahl Salt‐Sensitive Rats Independent of Systemic Blood Pressure
Authors: Irsik Debra , Ocasio Hiram , Sun Jingping , Chen Jian‐Kang , O'Connor Paul
Published: June 2021

Lower serum HCO3‐ concentrations are associated with a higher risk of progressive renal function loss and alkaline therapy improves renal outcomes in hypertensive patients. Experimental models are needed to better understand the mechanisms that mediate the beneficial outcomes of HCO3‐ supplementation on the kidney. We tested whether bicarbonate supplementation attenuates hypertension‐induced renal injury in the Dahl salt‐sensitive (SS) rat model. 10 week old male Dahl SS rats received either 0.1 M NaHCO3or equimolar NaCl (control) given through drinking water over the course of the experiment (n=6‐7 rats/group). After 4 days of measurement on 0.4% NaCl (low salt (LS)) chow, rats were fed a high salt (8% NaCl (HS)) diet for 2 additional weeks. Blood pressure was continuously measured via radio‐telemetry and urine collected weekly. Urinary Na excretion was not different between groups. High salt feeding resulted in a similar increase in mean arterial pressure (MAP) in control (Day 14 HS; 142.5±6.8) and HCO3‐ treated groups (Day 14 HS: 138.9±3.4; p=NS). Despite similar MAP responses, HCO3‐ supplemented animals had reduced glomerular sclerosis (4.1±0.5 vs 8.3±2.0 % sclerosed glomeruli; P=0.052), outer medullary protein casts (1.2±0.3 vs 5.1±1.3 % medullary cast area; P=0.014) and 24 hour protein excretion on Day 14 of HS, 12.8±3.1 vs 47.4 ±18.7 mg day 14 HS; P=0.03) respectively, compared to control group. We conclude that HCO3‐ supplementation protects from renal injury in high salt fed Dahl salt‐sensitive rats, independent of systemic blood pressure.
Regulation of Blood Pressure by the Calcineurin Homologous Protein‐1
Authors: Di Sole Francesca , Escano Crisanto , Babich Victor
Published: June 2021

Hypertension has high incidence and health care cost. Its treatments are often ineffective; therefore, we are in need of new strategies to prevent, limit or reverse hypertension. Long‐term regulation of blood pressure (BP) has fundamental renal components; in particular, the causes of impaired renal Na+ handling and possible strategies to overcome disturbances in renal Na+ balance in hypertension are not well defined. Recently, we have shown that a Ca2+‐binding protein, the Calcineurin Homologous Protein‐1 (CHP1), is a regulatory binding partner of a key player in the control of Na+ homeostasis, the epithelial brush‐border Na+/H+ exchanger‐3 (NHE3). Here, we proposed that CHP1 expression controls BP as a regulatory co‐factor of NHE3 transport. Indeed, selective renal silencing of Chp1 via renal subcapsular infusion of Chp1 siRNA in Balb/cJ mice significantly reduced NHE3 protein expression (‐50%). Importantly, Chp1 siRNA treated mice had a reduced systolic blood pressure compared to scrambled siRNA treated mice (‐30%). Chp1 siRNA treated mice also had markedly reduced serum Na+ and increased urinary Na+ excretion compared to scrambled siRNA treated mice. Serum K+ and Cl‐ did not change while urinary K+ and Cl‐ excretion were increased in Chp1 siRNA treated mice. Glomerular Filtration Rate estimated by creatinine clearance was reduced in Chp1 treated mice possibly as consequence of tubuloglomerular feedback. This is the first animal model in mammals where the effect of a reduction in CHP1 protein expression in the kidney was studied. Our findings provide new insights into the action of CHP1 on renal tubular Na+ transport and propose CHP1 protein expression as a novel tool to significantly control blood pressure.
Hypertensive and Renal Injury Responses to Nitric Oxide deficiency are Unaffected by Tyrosine Kinase Inhibition in Mice
Authors: Majid Dewan , Kadowitz Philip , Castillo Alexander
Published: June 2021

Tyrosine kinases act as second messengers that play a prominent role in intracellular signaling induced by inflammatory responses. Nitric oxide (NO) deficiency leads to hypertension (HTN) and associated inflammatory renal injury (RI). To examine the role for TKs in NO deficient form of HTN and RI, the responses to chronic administration of a NO synthase inhibitor, nitro‐L‐arginine methyl ester (L‐NAME; 100 mg/kg/day) for 4 weeks were evaluated in mice (n=7 in each group) treated with or without a tyrosine kinase inhibitor, Imatinib (75 mg/kg/day). Both the drugs were given in the drinking water. Systemic blood pressure (SBP) was measured by tail‐cuff plethysmography and a 24 hr urine collection was made using metabolic cages at the start (0 day) as well as every 7th day of the experimental period. At the end of the 4 wk period, the mice were sacrificed and kidneys were isolated to determine the renal injury scores (glomerulosclerosis, GS by PAS staining and renal interstitial fibrosis, RIF by Trichrome staining). L‐NAME treatment for 4 wks increased mean SBP (107± 3 mmHg) compared to that in control mice (88±2 mmHg). Imatinib co‐treatment did not alter significantly this SBP response to L‐NAME (103±4 mmHg). No significant differences were observed between the changes in urinary sodium, potassium or protein excretion rates in the L‐NAME and the L‐NAME+Imatinib treated mice. Compared to control mice, L‐NAME treated mice have significantly higher scores for GS (7.5±1.5 vs 3.7±0.4%) and RIF (3.0±0.7 vs 0.8±0.1%) which is similar in mice co‐treated with Imatinib (GS, 6.2±0.5% and RIF, 2.2±0.4%). These data suggest that the mechanism involved in the HTN and RI responses to NO inhibition is mostly independent of tyrosine kinase activation.
Effects of fructose feeding on mice with dual knockout of the insulin and insulin‐like‐growth factor, type 1 (IGF1) receptors from proximal‐tubule
Authors: Doh Kwame , Li Lijun , Ecelbarger Carolyn
Published: June 2021

The proximal tubule (PT) metabolizes fructose. How insulin and/or IGF1 regulate this metabolism is unclear. We bred mice with dual knockout (KO) of receptors for insulin and IGF1 from PT by Cre‐lox recombination using a g‐glutamyl transferase promoter. Wild‐type (WT) and KO mice (n = 5‐7/genotype) of both sexes were fed control (C) or high fructose (Fr) diet (60%) for 4 weeks in 2 studies. Data for males and females were combined except when sex differences were found. In Study 1 (young mice, 3‐4 month‐old) semi‐fasting blood glucose (BG) was significantly higher in KO (20‐30%, p = 0.007, by 2‐way ANOVA), but not affected by fructose. In Study 2 (mid‐aged, 6‐10 month‐old), BG was increased by fructose, but only in KO mice (significant interaction). Western blotting of whole kidney homogenates (WKH) in Study 2 revealed that Fr increased band density for IGF1R over 2.5‐fold, but only in WT mice. In contrast, KOFr mice actually showed a reduction in band density with fructose (~30% of KOC, p <0.001 for interaction). Similarly, ketohexokinase (KHK), the first enzyme in fructose metabolism, was significantly increased in expression by fructose (2‐fold p <0.014) in WT mice, but decreased in KO (significant interaction, p = 0.022). In contrast the expression of GLUT5, a fructose transporter, was significantly increased by Fr (6‐20%) in both genotypes (p = 0.007 for diet). These studies suggest IR or IGF1R may have a role in mediating fructose metabolism by the PT. Furthermore the absence of the receptor(s) in PT may predispose individuals to hyperglycemia. Whether metabolism of fructose in PT affects gluconeogenesis at this site is in need of further study.