bluuebunny/crossref_metadata_2025 huggingface dataset:
PGC‐1α Activation Confers Plasticity in the Mediator of Dilation in Healthy and Diseased Human Arterioles
Authors: Kadlec Andrew , Hockenberry Joseph C. , Beyer Andreas M. , Gutterman David D.
Published: November 2023

Background

Coronary artery disease (CAD) and increased intraluminal pressure (IILP) shift the mediator of flow‐induced dilation (FID) from nitric oxide (NO) to hydrogen peroxide (H2O2) in the human microcirculation. PGC‐1α, a master regulator of mitochondrial biogenesis, regulates reactive oxygen species (ROS) production and blood pressure. PGC‐1α is decreased in vessels from CAD patients. It is not known whether this important regulator of cell function is critically involved in endothelial‐mediated changes in vascular tone.

Objective

To determine whether a stimulated increase in PGC‐1α levels can restore NO as the mediator of dilation in healthy vessels exposed to IILP, and in CAD vessels.

Methods

Human adipose arterioles were incubated overnight with ZLN005, a novel transcriptional activator of PGC‐1α, and subsequently cannulated on glass micropipettes. Healthy (non‐CAD) vessels were exposed to physiological pressure conditions (60mmHg) or IILP (150mmHg for 30 min). Diseased (CAD) vessels were only exposed to 60mmHg pressure. Dilation was elicited by flow in the absence and presence of a nitric oxide synthase inhibitor, L‐NAME (10−4 M), a H2O2 inhibitor, PEG‐catalase (500 units/mL), or both to determine the mediator of dilation. Fluorescence microscopy using intraluminal MitoPY1 probed for H2O2 production in response to IILP.

Results

In healthy vessels treated with ZLN, a trend toward a reduction in FID from control was observed after addition of either L‐NAME or PEG‐catalase under physiological pressure conditions (n=6–8; NS). PEG‐catalase alone reduced FID after IILP (n=7; P < 0.05), with a similar trend in unstressed vessels from patients with CAD (n=9; NS). Complete inhibition of FID was observed in PGC‐1α‐activated vessels after addition of both L‐NAME and PEG‐catalase and in vessels from subjects with CAD (n=8; P < 0.05) or without CAD under physiological pressure conditions (n=6; P < 0.05). Fluorescence data confirmed that H2O2 production persisted after IILP in healthy treated vessels.

Conclusion and Significance

In contrast to the exclusively NO‐or H2O2‐mediated dilation seen in healthy or diseased conditions, respectively, activation of PGC‐1α with ZLN005 allows both NO and H2O2 to simultaneously contribute to dilation under basal pressure conditions and in the presence of CAD, but not after acute high pressure stress. These data provide support for the notion that dilation may be potentiated by more than one factor in the human microcirculation and that PGC‐1α may regulate plasticity in the mechanism of dilation in health and disease.

Support or Funding Information

Funding support provided by R01‐HL‐113612 (to D. D. Gutterman) and T32‐GM‐08020206 [Medical Scientist Training Program Grant] (to J. T. Barbieri)
Effect of pulmonary flow heterogeneity and impaired diffusing capacity on oxygen uptake
Authors: Roy Tuhin K , Secomb Timothy W
Published: November 2023

Severe impairment of oxygenation in critically ill patients is a major cause of morbidity and mortality, and can occur even with normal alveolar ventilation and cardiac output under conditions of decreased diffusing capacity or increased flow heterogeneity. A theoretical model of pulmonary oxygen uptake under resting conditions is used to simulate decreased diffusing capacity (DL) as well as increased heterogeneity (characterized by an increase in the coefficient of variation [CV] of pulmonary capillary blood flow), with the assumed normal value of CV based on observations of microvascular networks. Under resting conditions with nominal values of DL and CV, the model predicts an oxygen saturation (SO2) of 97% (PO2 = 94 mmHg). Simulating a 10‐fold reduction in DL leads to an SO2 of 85% (PO2 = 51 mmHg), whereas doubling the CV from its normal value leads to an SO2 of 95% (PO2 = 78 mmHg); both of these predictions suggest a high degree of reserve in the healthy resting lung. However, simulating these conditions simultaneously leads to a large reduction in SO2 to 71% (PO2 = 37 mmHg), exhausting the reserve capacity of the lung and demonstrating the detrimental synergistic effect of heterogeneity in the context of an attenuated diffusing capacity. These results imply that a combination of increased heterogeneity and decreased diffusing capacity can explain the severe impairment in pulmonary oxygen uptake and decreased saturations seen in critical illness.

Support or Funding Information

Supported by NIH grant HL070657.
Geometric and Topological Analysis of Arteriolar Networks in the Rat Gluteus Maximus Muscle: One Network to Rule Them All?
Authors: Al Tarhuni Mohammed , Goldman Daniel , Jackson Dwayne N
Published: November 2023

Introduction

A detailed evaluation of in vivo geometry and topology of skeletal muscle arteriolar networks is essential to understanding microvascular blood flow regulation. Beyond increasing understanding of skeletal muscle hemodynamics, such data provides critical experimental inputs for theoretical blood flow simulation studies. Generally, past studies have relied on data collected from vascular casting experiments or data collected from incomplete microvascular trees or segments. The objective of this study was to comprehensively analyze the geometry and topology of complete arteriolar networks within the rat gluteus maximus (GM) muscle. The data generated were used to generate an index of geometric/topological homology across GM networks and produce essential experimental data to use as inputs for future theoretical studies of hemodynamics.

Methods

The rat GM provides the ideal experimental model to study locomotive skeletal muscle. Its planar geometry and uniform thinness enable access (within a single focal plane) to its entire microcirculation for microscopic imaging and perturbation. Using intravital videomicroscopy, the GM (n=4) was scanned under baseline conditions and photomontages were compiled (~400 images per network). Photomontages were registered to a MATLAB x–y coordinate system and scaled digital networks were generated. Arteriolar diameters and lengths were measured along the arteriolar network and a centrifugal ordering algorithm was applied, resulting in arterioles ranging from 1st (feed) to 9th (terminal) order. Mean diameters, lengths, and number of segments were outputted and grouped with respect to arteriolar order.

Results

The coefficients of variation at each order were consistently greater for lengths than diameters. The relationships of arteriolar diameter and segment length as a function of vessel order were fitted with an exponential decay function and resulted in relatively stronger goodness of fit values for diameters (R2 = 0.62 to 0.75) than lengths (R2 = 0.32 to 0.53), suggesting greater predictability and homology between arteriolar diameter and vessel order. Topological analyses were extended to plotting the logarithm of diameters and lengths as a function of vessel order in an effort to validate Horton's laws in the GM and derive diameter, length, and bifurcation ratios. Finally, a “mean” arteriolar network that describes all relevant geometric and topological parameters was explored.

Conclusion

This study provides the first comprehensive analysis of rat GM topology and geometry. The data presented herein will serve as ideal experimental inputs for future computational studies of skeletal muscle hemodynamics and microvascular blood flow regulation.

Support or Funding Information

NSERC
Global Cerebrovascular Dysfunction in the Metabolic Syndrome Following Ischemic Stroke
Authors: Branyan Kayla , Brooks Steve , DeVallance Evan , Asano Shinichi , Frisbee Jefferson , Chantler Paul
Published: November 2023

Insulin resistance is suggested to impact endothelial function by attenuating nitric oxide (NO) synthase activity, which is important for blood flow control. This reduction in insulin sensitivity and decrease in endothelial function leads to an increased risk for poor cardiovascular outcomes such as stroke. Many studies have examined the ipsilateral middle cerebral artery (MCA) to determine the effect of stroke on the cerebral microvasculature. Neither the contralateral MCA, nor the posterior cerebral arteries (PCA) have been thoroughly scrutinized to determine the more global impact of stroke on cerebrovascular function. Obese Zucker rats (OZRs) are used as a representative model of insulin resistance, where their lean counterparts (LZRs) are considered healthy controls. To look at the possible effect of decreased NO bioavailability on the ipsilateral and contralateral hemispheres of the brain, OZRs and LZRs were induced with stroke by transient middle cerebral artery occlusion (tMCAO) for 60 minutes. The purpose of this study was to compare the reactivity of both the ipsilateral and contralateral MCAs and PCAs at 24 hours post‐stroke to determine if stroke impacted the cerebral hemispheres differently. OZRs and LZRs were separated into sham and tMCAO groups. The ipsilateral and contralateral MCA and PCA were isolated and hung in a pressurized microvessel myobath. To assess endothelial function, the MCAs and PCAs were exposed to increasing doses of acetylcholine. A DAF‐FM diacetate assay was used to detect the amount of NO production in the aorta as a representative measure of NO synthesis within the vasculature. After 24 hours, LZR tMCAOs had lower NO production than the sham animals (p<0.05) but OZR tMCAOs did not have a significant decrease in NO release. LZR and OZR tMCAOs had similar NO production values after 24 hours. Both groups had decreases in their MCA and PCA reactivity 24 hours post‐stroke (p<0.05). In the MCAs, ipsilateral reactivity was lower in OZRs than in LZRs. This effect was not seen in the PCA, where both the contralateral and ipsilateral had similar decreases in reactivity in LZRs. OZR ipsilateral PCA reactivity was further attenuated from the contralateral (p<0.05). OZR MCA reactivity was improved by incubation with TEMPOL but not LZRs. This same effect was not seen in PCAs where TEMPOL did not improve dilation in either group. The results from this study suggest that NO bioavailability is important for endothelial function after an ischemic stroke. It also suggests that both hemispheres of the brain are affected by stroke, although not to the same degree. Likewise, vessels such as the PCA are also impaired by occlusion of the MCA suggesting a more global effect on the cerebral microvasculature.

Support or Funding Information

AHA

NIH
Activation of RhoA, but not Rac1, mediates early stages of S1P‐induced endothelial barrier enhancement
Authors: Zhang Xun , Adderley Shaquria , Breslin Jerome
Published: November 2023

Compromised endothelial barrier function is a hallmark of inflammation. Rho family GTPases are critical in regulating endothelial barrier function, yet their precise roles, particularly in sphingosine‐1‐phosphate (S1P)‐induced endothelial barrier enhancement, remain elusive. We tested the roles of Rac1 and RhoA in this study. Confluent cultures of human umbilical vein endothelial cells (HUVEC) or human dermal microvascular endothelial cells (HDMEC) were used to model the endothelial barrier. Barrier function was assessed by determining the transendothelial electrical resistance (TER) using an electrical cell‐substrate impedance sensor. The results show that pharmacologic inhibition of Rac1 with 50 μM Rac1 Inhibitor II failed to block barrier enhancement elicited by 2 μM S1P. Likewise, expression of a dominant negative form of Rac1, or knockdown of native Rac1 with siRNA, failed to block S1P‐induced elevations in TER. In contrast, blockade of RhoA with the combination of the inhibitors Rhosin and Y16 (6.25 μM respectively) significantly reduced S1P‐induced increases in TER. Assessment of RhoA activation in real time using a fluorescence resonance energy transfer (FRET) biosensor showed that S1P increased RhoA activation primarily at the edges of cells, near junctions. This was complemented by myosin light chain‐2 phosphorylation at cell edges, which could be blocked with Y16 and Rhosin treatment. The results suggest that S1P causes activation of RhoA at the cell periphery, stimulating local phosphorylation of MLC, and resulting in endothelial barrier enhancement. S1P‐induced Rac1 activation, however, does not appear to have a significant role in this process.

Support or Funding Information

Supported by NIH Grant R01HL098215
Nrf2 Deficiency Attenuates Synaptic Plasticity in Mice, Mimicking the Aging Phenotype
Authors: Valcarcel‐Ares Marta Noa , Tucsek Zsuzsanna , Tarantini Stefano , Hertelendy Peter , Gautam Tripti , Sonntag William E , Deak Ferenc , Ungvari Zoltan , Csiszar Anna
Published: November 2023

There is increasing evidence that Nrf2/ARE signaling regulates lifespan and/or health span both in model organisms and laboratory rodents. Aging is associated with progressive Nrf2 dysfunction, impairing cellular resilience and promoting oxidative stress and inflammation. Age‐dependent impairment in the induction of hippocampal long‐term potentiation (LTP) is well documented, providing a likely neural basis for age‐related decline in learning and memory. While previous studies showed that Nrf2 dysfunction promotes neuronal death and administration of Nrf2 activators improve learning and memory in aged rodents, the effects of age‐related Nrf2 dysfunction on synaptic function are not well understood. To determine the effect of Nrf2 deficiency on cognition and synaptic plasticity, we compared performance of Nrf2−/− and control mice on various behavioral tests including the elevated plus maze, the radial arm water maze (RAWM) and novel object recognition test. To determine whether Nrf2 deficiency compromises neuronal mechanisms of learning and memory, extracellular recordings were performed from acute hippocampal slices using multi‐electrode arrays. Field excitatory post‐synaptic potentials were invoked through stimulation of the Schaffer collateral and obtained from the CA1 area. We found that Nrf2−/− mice have a reduced LTP elicited by high frequency stimulation in hippocampal slices. Reduced LTP in Nrf2−/− mice was associated with a compromised performance in the elevated plus maze learning test and the novel object recognition test. Together, these results provide additional evidence that intact Nrf2 signaling importantly contributes to brain health, preserving hippocampal synaptic plasticity and cognitive function. Further studies are needed to elucidate the neuronal mechanisms impacted by Nrf2 deficiency, determining the potential roles of oxidative stress and inflammatory processes.

Support or Funding Information

This work was supported by grants from the American Heart Association and the National Institute on Aging
Effects of Serelaxin on Renal Microcirculation in Rats under Control and High Angiotensin Environments
Authors: Shao Weijian , Prieto Minolfa C. , Gonzalez‐Arancibia Camila , Navar L. Gabriel
Published: November 2023

Serelaxin is a novel recombinant human relaxin‐2 that is being investigated for the treatment of heart failure. However, the effects on renal function, especially on renal microcirculation remain uncertain. Immunofluorescence studies localized RXFP1,2 and 3 receptors on endothelial cells, vascular smooth muscle cells, mesangial and collecting duct cells. Therefore we investigated the effects of serelaxin on the renal microvasculature under normal conditions and in presence of exogenous angiotensin (Ang) II levels. Clearance experiments were performed in male pentobarbital anesthetized Sprague‐Dawley normotensive (n=5) and Ang II infused rats (3ng/min, n=5). In control rats, serelaxin (5ug/100g body weight/hr) significantly increased mean arterial pressure (119±1.7 vs. 135±1.1 mmHg; P<0.05), renal blood flow (7.5±0.2 vs. 9.5±0.2 ml/min/g; P<0.05), urine flow (5.1±0.1 vs. 9.9±0.9 μl/min/g; P<0.05) and sodium excretion rates (0.12±0.01 vs. 2.15±0.19 μmol/min/g; P<0.05) without significant changes in GFR (1.26±0.04 vs. 1.38±0.03 ml/min/g). During infusion with subthreshold Ang II infused rats, serelaxin did not alter mean arterial pressure (122±1.3 vs. 126±0.7 mmHg), renal blood flow (9.3±0.2 vs. 10.1±0.3 ml/min/g) or urine flow (4.7±0.2 vs. 4.9±0.3 μl/min/g). However, the increases in sodium excretion rate were sustained (0.4±0.05 vs. 1.18±0.16 μmol/min/g; P<0.05). Serelaxin did not significantly alter GFR in Ang II infused rats (1.27±0.12 vs. 1.4±0.09 ml/min/g). Heart rates were elevated by serelaxin infusion in both control rats (373±8.2 vs. 508±2.9 beat/min; P< 0.05) and in Ang II infused rats (460±7.4 vs. 512±5.1 beat/min; P<0.05). Using the in vitro isolated juxtamedullary nephron preparation, the effects of serelaxin on afferent and efferent arteriolar diameters from control rat kidneys and during Ang II superfusion were assessed with videomicroscopy. In control rat kidneys, serelaxin (20, 40 ng/ml infusion in blood) significantly dilated afferent arterioles (10.8±1.2 vs. 12.2±1.2 and 13.7±1.2 μm; n=5; P<0.05) and efferent arterioles (9.7±0.9 vs. 11.4±1.1 and 12.0±0.9 μm; n=5; P<0.5). During Ang II superfusion (0.5nM), serelaxin (20, 40 ng/ml infusion in blood) had no effects on afferent arteriolar diameters (11.5±0.1 vs. 11.7±0.1, 11.8±0.1 μm; n=4). These results demonstrate that serelaxin has direct dilating actions on both pre‐ and post‐glomerular arterioles. In the presence of exogenous Ang II levels, the effects of serelaxin were prevented. The responses of the renal microvasculature may be related to changes in NO bioavailability and oxidative stress. In conclusion, serelaxin increases overall renal blood flow, urine flow and sodium excretion by dilating both pre and post glomerular arterioles in control conditions, but these effects are attenuated in the presence of exogenous Ang II.

Support or Funding Information

This study was supported by Novartis Pharmaceuticals Corporation.
Role of cerebrovascular endothelial dysfunction and oxidative/nitrative stress in impaired functional hyperemia: implications for age‐related vascular cognitive impairment
Authors: Tarantini Stefano , Toth Peter Joseph , Davila Antonio , Valcarcel‐Ares Marta Noa , Tucsek Zsuzsanna , Varamini Behzad , Ballabh Praveen , Sonntag William E , Baur Joseph A , Csiszar Anna , Ungvari Zoltan
Published: November 2023

Previous studies demonstrate that aging and pathological conditions associated with accelerated cerebromicrovascular aging (e.g. hypertension, obesity) promote cerebrovascular dysfunction by decreasing bioavailability of NO and increasing production of O2. − and reactive nitrogen species. Impairment of moment‐to‐moment adjustment of cerebral blood flow (CBF) via neurovascular coupling is thought to play a critical role in the genesis of cognitive impairment associated with the aforementioned conditions and previous studies demonstrate that endothelial dysfunction plays a critical role in neurovascular uncoupling in these conditions. Despite these advances, the role of endothelial NO mediation in neurovascular coupling responses is not well understood. To establish the link between endothelial function and functional hyperemia, neurovascular coupling responses were studied in mutant mice overexpressing or deficient in eNOS and the role of P2Y1 receptors in purinergic glioendothelial coupling was assessed. We found that genetic depletion of eNOS (eNOS−/−) and pharmacological inhibition of NO synthesis significantly decreased the CBF responses in the somatosensory cortex evoked by whisker stimulation and by administration of ATP, mimicking oxidative/nitrative stress‐mediated impairment of functional hyperemia and microvascular endothelial responses observed in aged mice. Overexpression of eNOS enhanced NO mediation of functional hyperemia. In control mice the selective and potent P2Y1 receptor antagonist MRS2179 attenuated both whisker stimulation‐induced and ATP‐mediated CBF responses, whereas in eNOS−/− mice the inhibitory effects of MRS2179 were blunted. Collectively, our findings provide additional evidence for purinergic glio‐endothelial coupling during neuronal activity, highlighting the role of ATP‐mediated activation of eNOS via P2Y1 receptors in functional hyperemia.

Support or Funding Information

This work was supported by grants from the American Heart Association, the National Center for Complementary and Alternative Medicine, and the National Institute on Aging
Mitochondrial Mechanisms of Nelfinavir Toxicity in Human Brain Microvascular Endothelial cells
Authors: Unis Graham , Baker Tyler P , Rajaprabhakaran Gowthamram , Sure Venkata N , Jain Neelesh P , Abraham Vihas M , Peterson Nicholas R , Gordon Angellica O , Chen Allen L , Cama Zeinab , Mondal Debasis , Katakam Prasad VG
Published: November 2023

Antiretroviral therapies with combinations of mechanistically different classes of drugs resulted in reduced HIV‐associated neurocognitive disorders, however, milder forms of cognitive disorders continue to be disabling in AIDS patients. Toxicity resulting from long‐term use of antiretroviral drugs have been implicated in the cognitive disorders but the exact underlying mechanisms are poorly understood. We hypothesized that nelfinavir, a protease inhibitor, causes the disruption of blood brain barrier (BBB) by promoting mitochondrial oxidative stress and impairing mitochondrial respiration. Our studies examined the effects of nelfinavir in human brain microvascular endothelial cells (BMECs). Cell viability following 48 h Nelfinavir treatment of hBMECs was determined using CCK‐8 assay. Measurements of superoxide levels were made by electron spin resonance spectrometery using spin probes for total (1‐Hydroxy‐3‐methoxycarbonyl‐2,2,5,5‐tetramethyl‐pyrrolidine) and mitochondrial superoxide (mito‐Tempo‐H). Oxygen consumption rates (OCR) were measured by Seahorse Analyzer. Transcellular endocytosis measurements were performed by using 40 kDa‐FITC‐dextran transfer in BMECs grown in transwells. Nelfinavir treatment caused an increase in cell proliferation of BMECs at low doses (0.5 μM‐1.5 μM) but decreased viability at high doses (5 μM‐10 μM). Nelfinavir at therapeutic doses promoted the generation of total and mitochondrial superoxide in BMECs. In addition, nelfinavir dose‐dependently diminished the basal OCR and reserve mitochondrial respiratory capacity in BMECs. Moreover, nelfinavir dose‐dependently promoted increased transcellular permeability in BMECs. Thus, nelfinavir induced mitochondrial oxidative stress promotes diminished mitochondrial respiratory capacity and decreased cell proliferation leading to the disruption of BBB.

Support or Funding Information

Support: PVK: Louisiana BoRSF‐RCS (LEQSF(2014‐17)‐RD‐A‐11) and AHA Scientist Development Grant (14SDG20490359); IR: AHA Postdoctoral Fellowship Grant (15POST23040005); and DWB: NIH grants (HL‐077731and HL093554).
Cardiovascular Implications of Environmental Stressors, a Health Call to Protect the Planet
Authors: Cabrales Pedro , William Alexander
Published: November 2023

A class of air pollutants known as atmospheric ligands (oxygen, O2; carbon monoxide, CO; nitric oxide, NO; and hydrogen sulfide, H2S) are associated to a variety of physiological process. At atmospheric concentrations below regulatory limits, these atmospheric ligands can be physiologically active. Previous studies have examined their implication on cardiovascular health outcomes at concentrations above US Environmental Protection Agency (EPA) limits. Our studies have focused on cardiovascular effects these gases within good to moderate EPA limits. Hamsters instrumented with dorsal window chambers, or with a miniaturized left ventricle pressure volume (LVPV) were used to study microvascular and systemic implications of acute and chronic exposure to these gases. Our results present the implications of atmosferic polutans on cardiovascular function. Due to the direct implications on health, humanizing the protection of the planet will emphasize the gravity of environmental preservation.

Support or Funding Information

P01‐HL110900, R01‐HL52684, and R56‐HL123015.
Nocturnal Blood Pressure Dipping in Normotensive Adults: Effect of Dietary Sodium and Sex
Authors: Brian Michael , Dalpaiz Ameg , Matthews Evan , Lennon‐Edwards Shannon , Edwards David , Farquhar William
Published: November 2023

Normal nocturnal blood pressure (BP) dipping is arbitrarily defined as a decrease in mean daytime to mean nighttime BP by 10% to 20%. Individuals that have impaired nocturnal BP dipping (i.e., <10%) have an increased risk of cerebrovascular and cardiovascular diseases. Excess sodium consumption is associated with increased cardiovascular disease risks and no studies have examined nocturnal BP dipping under a controlled sodium diet.

PURPOSE

To assess nocturnal BP dipping during low (LS) and high sodium (HS) diets in men and women. We hypothesized that a HS diet would impair nocturnal BP dipping, and men would have a greater impairment than women.

METHODS

Eighty‐seven healthy normotensive men (n = 41; age: 35 ± 2 years) and women (n = 46; age: 40 ± 2 years) participated in a controlled feeding study where LS (20 mmol Na+/day) and HS (300 mmol Na+/day) diets were provided for 7 days each in random order. Subjects wore a 24‐hour ambulatory BP monitor, and we collected a 24‐hour urine sample and fasted blood sample on the final day of each diet. Nocturnal BP dipping was calculated as: ((mean daytime BP – mean nighttime BP)/mean daytime pressure)*100.

RESULTS

As expected, there was a significant increase in urinary sodium excretion during the HS diet (women: LS = 26.0 ± 2.1 vs. HS = 238.4 ± 14.1 mmol/24hr; men: LS = 31.5 ± 4.4 vs. HS = 234.4 ± 13.3 mmol/24hr; p < 0.01) and serum sodium (women: LS = 137.7 ± 0.3 vs. HS = 139.7 ± 0.2 mmol/L; men: LS 137.9 ± 0.4 vs. HS = 139.8 ± 0.3; p < 0.05) with no differences observed between the sexes. Nocturnal BP dipping was not different between the diets (women: LS = 10 ± 1% vs. HS = 10 ± 1% mmHg; men: LS = 9 ± 1% vs. HS = 10 ± 1% mmHg; p > 0.05) with no differences observed between the sexes.

CONCLUSION

Our findings suggest that increased dietary sodium does not influence nocturnal BP dipping responses in normotensive men and women.

Support or Funding Information

NIH Grant R01 HL104106
Divergent response of circulating CTRP3 levels to obesity between males and females
Authors: Peterson Jonathan M. , Wagner Roy Marshall , Sivagnanam Kamesh , Clark William Andrew
Published: November 2023

C1q TNF alpha related Protein 3 (CTRP3) is a novel adipose tissue derived secreted factor, or adipokine. CTRP3 has been linked to a number of beneficial biological effects on metabolism, inflammation, and survival signaling in a variety of tissues. However, very little is known about CTRP3 in regards to human health. The purpose of this project was to examine circulating CTRP3 levels in a clinical population. It was hypothesized that serum CTRP3 levels would be decreased with obesity and diabetes.

Methods

body mass index (BMI), diabetes status, and plasma samples were collected from 100 patients who were >30 years of age and presented at the East Tennessee State University Heart Clinic with symptoms requiring heart catheterization in order to identify the presence of cardiovascular blockages (n=51 male, n=49 female). Circulating CTRP3 levels were quantified using commercially available ELISA.

Results

Circulating concentrations of CTRP3 were significantly higher in normal weight (BMI <30) females (1.65 ± 0.24 μg/ml) compared with males (1.05 ± 0.12 μg/ml). Interestingly obesity (BMI >30) resulted in an increase in circulating CTRP3 levels in male subjects (1.52 ± 0.16 ug/ml) but showed a significant decrease in female subjects (1.11 ± 0.15 μg/ml). Additionally, there was a significant reduction in circulating CTRP3 levels in female subjects who were diagnosed with diabetes compared with patients without diabetes (1.50 ± 0.12 vs. 0.812 ± 0.10 μg/ml). There was no relationship between diabetes status and circulating CTRP3 levels in male subjects.

Conclusion

Circulating CTRP3 levels had a different relationship with diabetes and obesity status between male and female patients. It is possible that circulating CTRP3 levels are controlled by hormonal status, however more research is needed to explore this relationship.

Support or Funding Information

College of Clinical and Rehabilitative Health Sciences, East Tennessee State University, Dean's Student Research Award
Wild Type p53 Regulates Endothelial Barrier Function by mediating Rac1 signaling and inhibiting RhoA activity
Authors: Barabutis Nektarios , Birmpas Charalampos , Thangjam Gagan , Gregory Betsy W , Clements Mary Ann , Newton Joseph , Catravas John D.
Published: November 2023

The tumor suppressor and heat shock protein 90 (hsp90) client protein, p53, is a transcription factor which is frequently mutated in human cancers. An emerging body of evidence suggests that p53 also induces strong anti‐inflammatory responses, both in vivo and in vitro. Such activities maintain and preserve vascular barrier function, a key element of lung integrity and defense against endogenous or exogenous insults. We have recently reported that p53 is a major regulator of vascular integrity and endothelial permeability mostly due to its inhibition of the barrier disruptive RhoA signaling. In the present study we further investigated the mechanisms underlying the barrier protective effects of p53. Nutlin‐ or hsp90 inhibitor‐ induced p53 overexpression increased Rac1 activity (GTP‐bound Rac1), a small GTPase with known barrier‐protective effects. Nutlin or hsp90 inhibitor also increased downstream LIMK1/2 phosphorylation/activation as well as cofilin phosphorylation/deactivation thus preventing actin stess fiber formation and promoting cortical actin. When p53 expression was suppressed by siRNA, the opposite effects were observed. Hsp90 inhibitor (AUY‐922)‐induced p53 overexpression also caused an induction of the RhoA negative regulator p190Rho‐GAP that led to inhibition of RhoA activity as well as inhibition of downstream MLC phosphorylation. Real time measurements of endothelial barrier function by continuous monitoring of transendothelial electrical resistance (TER) of human lung microvascular endothelial monolayers revealed a prominent role of p53 in endothelial barrier regulation. Downregulation of p53 by pifithrin attenuated AUY‐922‐induced barrier enhancement, whereas siRNA‐mediated p190Rho‐GAP silencing led to an enhanced LPS‐induced decrease in TER. In conclusion, we propose that p53 regulates vascular barrier function by manipulating the balance of the actin remodeling Rac1 and RhoA pathways.

Support or Funding Information

This study was supported by National Heart, Lung, and Blood Institute Grants HL101902 and HL93460.
High intensity one‐legged cycling improves functional sympatholysis and aerobic fitness in chronic heart failure
Authors: Munch Gregers Druedal Wibe , Jepsen Ulrik Winning , Pedersen Bente Klarlund , Rosenmeier Jaya , Mortensen Stefan Peter
Published: November 2023

Exercise intolerance and fatigue during daily activities are primary symptoms in patients with chronic heart failure (CHF). The poor correlation between the hemodynamic parameters of left ventricular performance and perceived symptoms suggests that other factors such as muscle mal perfusion plays a role in determining exercise capacity. The purpose of this study was to investigate the peripheral hemodynamic response to high intense one‐legged cycling. Leg hemodynamics were measured before and after 6 weeks of high intensity interval one‐legged cycling (90% one‐legged cycling max 4×4 min intervals with each leg, 3 times per week) in seven heart failure patients (age: 58±4 years; LVEF 34±5%; BMI 25.8±1.8 kg/m2; VO2 peak: 2.1±0.2 l/min) at rest and during one‐legged knee extensions with without arterial tyramine infusion. Data were analyzed by repeated measures two‐way ANOVA and Tuckey's honestly significant difference (HSD) post hoc procedure. Exercise training increased VO2 peak (2.2±0.2 vs. 2.5±0.3 l/min: P<0.05), Wattmax during two‐legged cycling (153±14 vs. 163±24 Watt; P<0.05), Wattmax during one‐legged knee extensor exercise (36±10 vs. 52±9 Watt; P<0.05) and 6 min walking distance (553±48 vs. 595±59 m; P<0.05). Arterial tyramine infusion lowered leg blood flow and leg vascular conduction at rest (P<0.05) with no difference before and after the training intervention. Arterial tyramine infusion during one‐legged knee extensions, lowered leg blood flow before the training intervention (P<0.05), whereas tyramine did not lower leg blood flow after the training intervention. These results suggest that high intensity one‐legged cycling improves functional sympatholysis during exercise and is beneficial for patients with chronic heart failure in regards to exercise capacity and functionality.
Sex Differences in Hypertension: A Modeling Study
Authors: Chen Ying , Edwards Aurelie , Sullivan Jennifer , Layton Anita
Published: November 2023

The goal of this study was to investigate sex differences in spontaneously hypertensive rats (SHR) and their effects on medullary oxygenation and oxidative stress. To accomplish that goal, we developed a detailed mathematical model of solute transport in the renal medulla of the rat kidney. The model represents the radial organization of the renal tubules and vessels, which centers around the vascular bundles in the outer medulla and around clusters of collecting ducts in the inner medulla. In addition, the model accounts for the biochemical reactions among O2, nitric oxide (NO), and superoxide (O2−). Model simulations yield significant radial gradients in interstitial fluid oxygen tension and NO and O2− concentration in the outer medulla and upper inner medulla. We conducted model simulations to assess the extent to which sex differences in SHR, including O2− production rate and anti‐oxidant capacity, contribute to the higher levels of oxidative stress and the lower levels NO bioavailability reported in male SHR.

Support or Funding Information

This research was supported in part by NIH grant DK‐89066.
Leptin‐Mediated Increases in Sympathetic Tone Decreases Alpha(1D)‐Adrenergic Receptor Expression in Arteries and Adrenals
Authors: Newell Maegan , Momtahan Mina , Kennard Simone , Belin de Chantemele Eric J.
Published: November 2023

Obesity is a major risk factor for hypertension with adipocyte‐derived leptin causing sympathoactivation. Deletion of protein tyrosine phosphatase 1B (PTP1B) is known to increase leptin sensitivity, making it an ideal model for studying the cardiovascular effects of leptin separate from obesity. Our lab has previously characterized the reduction of a1D‐adrenergic receptor expression and reactivity in the aorta that accompanies leptin‐mediated increases in vascular sympathetic tone. Directly implicated in sympathetic regulation of blood pressure through vasoconstriction, the decreased expression and reactivity of the α1D receptor is suggestive of adrenergic desensitization as a protective mechanism against the development of hypertension. This study tested the hypothesis that, in addition to the aorta, leptin‐induced, sympatho‐mediated decreased adrenergic receptor expression occurs in vascular beds and most prominently in those associated with blood pressure regulation as well as in the norepinephrine‐and epinephrine‐releasing adrenals. Real‐time PCR conducted on tissues collected from wild‐type (WT) and PTP1B knockout animals (KO) revealed that leptin‐mediated increases in sympathetic tone decreased α1D‐receptor expression in aorta (WT: 1.08±0.15 vs. KO: 0.84±0.15), adrenals (WT: 1.08±0.12 vs. KO: 0.67±0.10), and renal (WT: 1.08±0.11 vs. KO: 0.87±0.11) and mesenteric arteries (WT: 1.15±0.24 vs. KO: 0.71±0.12). Additionally, this study investigated the distribution of α1D receptors among tissues and found tenfold and thirtyfold increased α1D receptor expression in the adrenals and renal arteries, respectively, and no statistical difference of the expression levels in the mesenteric arteries as compared to the aorta. These data support the hypothesis that leptin‐mediated sympatho‐activation decreases adrenergic receptor expression and highlights the adrenals and renal arteries as potential pathway targets for leptin‐induced sympathoactivation.
ACE2 Deletion is Associated with Increased ADAM17 and Reduced Inhibitory Currents to Pre‐sympathetic Hypothalamic Neurons
Authors: Mukerjee Snigdha , Xu Jiaxi , Sriramula Srinivas , Gao Hong , Zsombok Andrea , Lazartigues Eric
Published: November 2023

Deletion of the Angiotensin Converting Enzyme type 2 (ACE2) leads to a genetic background‐dependent increase in baseline blood pressure in mice, which can reach hypertensive levels with age. Recently, we identified a disintegrin and metalloprotease 17 (ADAM17) as a new member of a signaling pathway leading to the development of neurogenic hypertension. In an attempt to pinpoint the origin of developing hypertension in ACE2 knockout mice, we hypothesized that enhanced sympathetic drive could originate from elevated ADAM17 in pre‐sympathetic neurons of the paraventricular nucleus (PVN) of hypothalamus. Adult (10–12 week‐old) wildtype (WT) and ACE2 knockout male mice were used to assess ADAM17 protein expression (immunohistochemistry, Western blot and qPCR) in the PVN while another group was injected in the kidney with a pseudorabies virus encoding a green fluorescent protein, for retrograde labeling of sympathetic neurons. After 4 days, whole‐cell patch‐clamp recordings were conducted from labeled pre‐sympathetic PVN neurons. The resting membrane potential of pre‐sympathetic PVN neurons in WT mice was −49.01 ± 2.09 mV, while −48.9 ± 0.2 mV in ACE2 knockout mice, which may suggest an increased threshold for excitability in pre‐sympathetic PVN neurons. Interestingly, when the inhibitory inputs were analyzed, miniature IPSC frequency was reduced in ACE2 KO compared to WT (0.68 ± 0.29 vs. 1.56 ± 0.28 Hz; P<0.05) suggesting that the ACE2 knockout mice might be more susceptible to excitation, thus contributing to a sympathetic overdrive. Within the hypothalamus, ADAM17 expression showed a 2‐fold increase in ACE2 knockout compared to WT mice (P<0.05). Using immunohistochemistry, increased ADAM17 expression was confirmed in parvocellular neurons of the PVN. Taken together, our data suggest that enhanced expression of ADAM17 in the parvocellular region of the PVN could be associated with increased excitability of pre‐sympathetic neurons in ACE2 knockout mice. This dysregulation in neuronal activity might alter the intricate pressor homeostasis leading to increased blood pressure. These results suggest that ADAM17 could be a potential new target for the reduction of enhanced sympathetic activity in neurogenic hypertension.

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NIH/NHLBI (HL093178) COBRE (P30GM106392)
G Protein‐Coupled Estrogen Receptor (GPER) Expression in The Kidney Of L‐NAME‐Induced Hypertension and 2K‐1C Rats
Authors: de Oliveira Sales Elizabeth Barbosa , Maruyama Nadia Oliveira , Varela Vanessa Araujo , Lucas Thais F. , Boim Mirian Aparecida , Porto Catarina Segreti , Bergamaschi Cassia Toledo , de Campos Ruy Ribeiro
Published: November 2023

Recent studies show that estrogen plays an important role in the structural and functional processes of the central nervous system and peripheral organs in the control of blood pressure. And also, provides renoprotective effects, which are dependent on the direct action of G protein‐coupled estrogen receptor (GPER) in the renal tubules. Here we evaluated the GPER protein expression levels and its location in the kidneys of rats with L‐NAME‐induced hypertension (n=6), 2 Kidney‐1Clip (2K‐1C) hypertension (n=5) and 2K‐1C treated with Losartan (n=5). The rats were treated with L‐NAME (20mg/Kg/day) and Losartan (30mg/Kg/day) by gavage for 7 consecutive days. The systolic blood pressure (SBP) was monitored using tail cuff recording method before and after the treatment to confirm the levels of blood pressure. The hypertension induced by L‐NAME was followed by up regulation of GPER (74,8%) in the kidney compared to SHAM group analyzed by western blotting. In addition, the immunohistochemistry analyses showed that this GPER increase was specific to renal medulla in this animals (L‐NAME: 32,5 % ± 2,6 vs. SHAM: 19,0 % ± 0,5). However, a significant decrease in GPER was showed in clipped kidney compared to the contralateral kidney in 2K‐1C model (Clipped: 110,0 % ± 5,8 vs. Contralateral:7 5,1% ± 6,5). And also, this reduction was specific to renal medulla in the clipped kidney (Contralateral: 14,6 % ± 0,6 vs. Clipped: 10,2 ± 1,6, P<0,05). Despite the Losartan reduced of SBP, the treatment unchanged the GPR30 expression in the kidney of 2R‐1C animals. Therefore, our findings suggest that the GPER shows protective function by increasing its expression in the hypertensive rats treated with L‐NAME. On the other hand, the reduction of GPER in the clipped kidney could be involved in the deleterious effects of renovascular hypertension on this organ. The mechanisms by which the GPER is modulated still need to be further investigated. However, our results demonstrate that GPER is not dependent of Ang II in renal tissue of renovascular animals.

Support or Funding Information

Supported by CAPES and FAPESP.
P2X Receptor‐Mediated Inhibition Of NaCl Absorption In The Thick Ascending Limb: No Evidence For Nitric Oxide As Second Messenger
Authors: Svendsen Samuel Levi , Olsen Jeppe Steen , Preatorius Helle , Leipziger Jens G
Published: November 2023

Background

Basolateral (bl.) P2X receptors acutely and markedly reduce NaCl absorption in mouse medullary thick ascending limb (mTAL). It has been proposed that P2X receptor mediate NO synthesis and subsequent NKCC2 inhibition. P2X receptor stimulation causes an increase in cytosolic Ca2+ and therefore this could be proximal to the generation of NO.

Objective

Here we tested if blocking NO synthesis, adding an NO donor or hindering Ca2+ influx affects the ATP‐mediated (P2X) transport inhibition.

Methods

We used isolated, perfused mTALs from mice to electrically measure NaCl absorption. By microelectrodes we determined the transepithelial voltage (Vte) and the transepithelial resistance (Rte) and via these the transepithelial Na+ absorption (equivalent short circuit current, I′sc).

Results

We confirm that bl. ATP (100μM) induced a marked, acute and reversible inhibition of Na+ absorption (28% ± 6%, n=6). In the presence of the NO synthase blocker L‐NAME (100 μM, ~4 min preincubation) the ATP effect remained unaffected (23% ± 9%, n=6). Also higher concentrations and longer incubation with L‐NAME (1 mM, 15min incubation) were without effect. High concentrations of L‐NAME (1 mM) per se reduced transport significantly. Acute addition of the NO donor SNAP (100μM, ~10 min) did not affect tubular transport. Furthermore, the removal of extracellular Ca2+ (100 nM, 2 min preincubation) had no effect on the ATP‐induced transport inhibition ([Ca2+ ]o=100nM: 21% ± 6%, n=5, [Ca2+]o=1μM: 24% ± 4%, n=6).

Conclusion

We find no evidence for nitric oxide (NO) as second messenger for P2X receptor‐dependent transport inhibition. Similarly, Ca2+ signaling appears not involved in the ATP effect. It remains undefined how P2X receptors trigger the marked reduction of transport in the TAL.
Expression of a Diverse Array of Ca2+‐Activated K+ Channels are Functionally Coupled to the Mechanosensitive TRPV4 Channel in the Late Distal Tubule
Authors: Li Yue , Hu Hongxiang , O'Neil Roger G
Published: November 2023

The voltage‐ and Ca2+‐activated, big conductance K+ channel (BK, maxi‐K channel) is known to be expressed in the distal tubule of kidney where it underlies flow‐ and Ca2+‐dependent K+ secretion in the connecting tubule (CNT) and cortical collecting duct (CCD). While the mechanosensitive TRPV4 channel is central for controlling Ca2+ influx, the potential role of other Ca2+‐activated K+ channels, KCa, in regulating K+ secretion in these cells is largely unknown. Using qPCR mRNA analysis and immunoblots of mouse kidney and the CCD cell line, mCCDcl1 (a K+ secreting cell line; Fodstad H et al., Am J Physiol 296:F966–75, 2009) an array of KCa channels was identified. Subsequent immunohistochemical staining for expressed ion channel proteins in CCD, CNT, and the mCCDcl1 cells, revealed expression of TRPV4 and three subfamilies of KCa channels: the small‐conductance SK channels (SK1 and SK3), the intermediate conductance IK channel (IK1), and the BK‐alpha channel. Intracellular Ca2+ imaging of mCCDcl1 cells demonstrated that the KCa channels were functionally regulated by TRPV4 and that each of the KCa channels displayed a potent functional cross‐talk with TRPV4 upon TRPV4 activation (GSK1016790A, 3–10 nM). Indeed, upon KCa channel activation induced by TRPV4, intracellular Ca2+ levels were suppressed upon inhibition of each given KCa channel subtype, SK, IK, BK, by addition of selective K+ channel inhibitors‐‐apamin (300 nM), TRAM‐34 (300 nM), or Iberiotoxin (100 nM), respectively. Further, for mCCDcl1 cells grown on permeable supports, activation of TRPV4 (GSK1016790A) induced a rapid decrease in transepithelial electrical resistance (TEER) that was partially restored by selective inhibition of each KCa subtype, SK, IK, and BK, as above. Immunohistochemcial staining of mouse CCD demonstrated expression of these channels in most cells, although significant differential staining of principle cells (PC) versus intercalated cells (IC) was apparent with the following staining patterns: TRPV4 PC>IC, BKa PC=IC, IK1 PC=IC, SK1 IC>>PC, and SK3 PC>>IC. It is concluded that an array of KCa channels are expressed in CNT and CCD and, like BK‐alpha, are functionally regulated by TRPV4‐mediated Ca2+ influx where strong cross‐talk between the KCa and TRPV4 exists. Further, it is postulated that with the high Ca2+ binding affinity of SK1/3 and IK1, these KCa channels will be activated early on during the initial induction of TRPV4. The observed functional cross‐talk will lead to early elevation in intracellular Ca2+ levels which will enhance activation of the low Ca2+ binding affinity channel, BK, and, in turn, give rise to enhanced BK‐mediated K+ secretion. Whether SK1/3 and IK1 directly participate in K+ secretion is likely, but remains to be verified in future studies.

Support or Funding Information

NIH R01 DK098401 AHA 14GRNT20380916