bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered electrolyte homeostasis in mice with collecting‐duct‐principal‐cell select knockout of the mammalian‐target‐of‐rapamycin (mTOR)
Authors: Ecelbarger Carolyn M. , Byrd Marcus , Tiwari Swasti , Li Lijun 
Published: November 2023

The mammalian‐target‐of‐rapamycin (mTOR) is a central sensor of energy status in many cell types. One of its primary regulators is insulin. In cell culture, mTOR has been demonstrated to play a role in insulin activation of the epithelial sodium channel (ENaC). To assess the role of mTOR on electrolyte homeostasis by the collecting duct (CD), we generated mice with CD‐principal‐cell select mTOR knockout (KO) by Cre‐lox recombination using the aquaporin‐2 promoter to drive Cre‐recombinase. No differences in body or kidney weights between KO and wild‐type (WT) littermates were observed. Adaptation to a low‐sodium (Na+) diet was assessed in young, male mice. As compared to WT, KO mice (n = 8/genotype) fed the low Na+ diet for one‐week had significantly lower plasma potassium (K+) levels (mM): 4.97 ± 0.24 (wild‐type, WT) versus 3.89 ± 0.14 (KO), p < 0.005, with no significant differences in plasma chloride (Cl−) or Na+. Likewise, no significant differences were found between genotypes for urine excretion of Na+, K+, or Cl− on days 1–3 of the low‐Na+ diet; however, there was a strong trend for a relatively higher urine K‐to‐Cl ratio on day 2 in the KO: 1.64 ± 0.18 (WT) versus 2.26 ± 0.24 (KO), p = 0.053 suggesting impaired homeostatic balance between K+ and Na+ in the KO. A benzamil‐sensitivity test was applied to KO and WT mice, as an assessment of basal ENaC activity, by administering 4.3 mg/kg·bw benzamil, intraperitoneally, and collecting urine for 4 hours. KO mice had significantly reduced urine Cl− concentrations (mM), as well as, absolute excretion of both Na+ and Cl− (mmol/4 hours), as compared to the WT, suggesting reduced basal ENaC activity. However, their urinary ratio of Na‐to‐Cl was higher: 1.37± 0.07 (WT) versus 1.71± 0.11 (KO), p = 0.023, supporting independent and distinct regulation of these two electrolytes by the mTOR pathway. Overall, these findings support a role for mTOR in the modulation of CD electrolyte homeostasis by ENaC and related but distinct Cl− and K+ transporters and channels.Support or Funding InformationSupported by Georgetown University CTSA award and internal funding.
Intermittent and Sustained Hypoxia Exacerbate the Neonatal Microglial Inflammatory Response to TLR4 Ligands
Authors: Kiernan Elizabeth A. , Gardner Alyssa , Langenstroer Elizabeth A. , Watters Jyoti J. 
Published: November 2023

Chronic intermittent hypoxia (IH) is a hallmark of sleep disordered breathing, a condition that occurs in approximately 2–4% of the pediatric population, and in over 50% of premature infants. IH is characterized by increased reactive oxygen species formation, peripheral and CNS inflammation, neuronal death and neurocognitive deficits. However, although IH alone does not promote neuroinflammation in the neonate to the extent it does in adults, few studies have investigated the possibility that IH may exacerbate the neonatal CNS response to systemic inflammation, a common clinical co‐morbidity, especially in premature infants. In neonatal rats, we tested the hypothesis that IH will prime both the peripheral and central immune system leading to potentiation of inflammation. To test this hypothesis, we exposed P1 rat pups to one night of IH (2 min cycles of 10.5% O2). The following morning the pups were challenged with an intraperitoneal injection of the toll‐like receptor 4 (TLR4) ligand lipopolysaccharide (LPS) for 3 hrs. CD11b+ microglia and macrophages were harvested from the brain and spleen, respectively, and iNOS and IL‐1 beta gene expression was analyzed. Preliminary results demonstrated that IH exposure prior to LPS injection increased microglial (but not spleen macrophage) iNOS mRNA levels compared to LPS alone. These findings were confirmed in vitro by exposing murine N9 and primary microglia to sustained hypoxia (1% O2 for 16 hrs) followed by application of multiple TLR4 ligands (LPS, Hsp60, HMGB1) for 3 hrs. Hypoxia potentiated TLR4‐dependent iNOS and IL‐1b mRNA levels, changes that were consistent with increased transcriptional activation marks at the iNOS gene promoter (trimethylation of histone H3 lysine 4; H3K4me3). Future studies will investigate if similar epigenetic modifications also occur in vivo. These data suggest differential responses of peripheral and CNS macrophage populations to the priming effects of hypoxia, and indicate that the CNS may be more vulnerable. By resolving mechanisms whereby hypoxia primes microglial inflammation, novel therapeutic targets can be identified that may be beneficial to an already susceptible pediatric population.Support or Funding InformationThis work was supported by NIH R01 HL111598 and NS085226
Counter‐regulation of the HIF‐dependent adaptive response to hypoxia by hypercapnia
Authors: Taylor Cormac , Selfridge Andrew , Cavadas Miguel , Scholz Carsten , Cambpell Eric , Welch Lynn , Lecuonah Emilia , Colgan Sean , Barrett Kim , Sporn Peter , Sznajder Jacob , Cummins Eoin 
Published: November 2023

Molecular O2 and CO2 are the primary substrate and product of oxidative metabolism respectively. Hypoxia (low O2) and hypercapnia (high CO2) are co‐incidental features of the microenvironment in a diverse range of pathophysiologic states including cancer, respiratory disease and inflammation. Hypoxia inducible factor (HIF) is the master transcriptional regulator of the response to low oxygen. Despite the close relationship between O2 and CO2 levels, the potential impact of CO2 on HIF remains unclear. Recent studies have demonstrated the ability of CO2 to regulate gene expression. The purpose of this work was to investigate the effect of hypercapnia on the HIF pathway.HIF‐2α protein and the HIF targets erythropoietin and carbonic anhydrase IX were decreased by hypercapnia in vivo. Hypercapnia suppressed HIF‐1α and HIF‐2α protein stabilization in a variety of cell lines of diverse origin. High CO2 diminished the activity of HIF‐dependent genes. CO2 did not impact the canonical, oxygen‐dependent HIF degradation pathway. Hypercapnia caused intracellular acidosis, and levels of HIF‐1/2α protein were lower when intracellular pH (pHi) was reduced by means other than CO2. Low pHi is required for optimal lysosomal degradation and a lysosomal inhibitor antagonised the ability of hypercapnia to reduce HIF‐1/2α.In conclusion, we have demonstrated a novel CO2‐dependent suppression of HIF signalling. As HIF regulates the transcription of a host of genes that have angiogenic, glycolytic and inflammatory functions, manipulating HIF with CO2 could be exploited for therapeutic gain.Support or Funding InformationThis work was supported by a grant from Science Foundation Ireland (11/PI/1005)
Can Augmented Sympathetic Activity in Rosacea be Tracked by Cutaneous Flowmotion?
Authors: Wilson Thad E. , Eaton Emily , Toma Kumika , Jurovcik Andrew , Sammons Dawn , Metzler‐Wilson Kristen 
Published: November 2023

Recent supraorbital microneurography evidence indicates that sympathetic outflow to the face is augmented in rosacea (Metzler‐Wilson & Toma, et al, J Neurophysiol, 2015). Our aim was to identify if non‐invasive assessment of skin blood flow (SkBF; laser‐Doppler flowmetry) can be used to track facial sympathetic outflow differences between subjects with and without rosacea and during symptom‐triggering events. To this end, we assessed spectral power (fast Fourier transform) in the sympathetic (low frequency (LF); 0.02–0.06 Hz) and vascular endothelial (very‐low frequency (VLF); 0.009–0.02 Hz) frequency ranges in forehead skin during systemic heating (50° C water delivered through a high density tube‐lined suit to increase mean skin and internal temperature). We hypothesized that compared to healthy age‐sex matched controls (n=9), Individuals with rosacea (n=9) would demonstrate greater changes in LF, but not VLF ranges. SkBF increased to a greater extent during heat stress in rosacea compared to controls (451±40 vs. 352±33% increase from baseline; p=0.04). Heat stress also increased spectral power within both the VLF and LF ranges in both groups (change from baseline to heating in VLF: 0.17±0.16 vs. 0.67±0.32 au; LF: 1.17±0.62 vs. 0.39±0.36 au; rosacea and control, respectively), but significant group difference were not observed (VLF: p=0.21; LF: p=0.16). High between‐subject variance existed in patients and controls. Thus, until better variability controls among subjects during symptom‐triggering events are developed, cutaneous flowmotion does not appear to be a viable surrogate for skin sympathetic nerve activity measurements in this population.Support or Funding InformationNational Rosacea Society
ATP Maintains the Ability to Blunt α1‐Adrenergic Vasoconstriction During Combined Blockade of Nitric Oxide, Prostaglandins, Na+/K+‐ATPase, and KIR Channels
Authors: Hearon Christopher M , Richards Jennifer C , Luckasen Gary J , Larson Dennis G , Joyner Michael J , Dinenno Frank A 
Published: November 2023

The vasoactive properties of exogenous adenosine triphosphate (ATP) are unique because it has the dual ability to induce robust vasodilation as well as blunt sympathetic vasoconstriction, similar to what is observed in contracting human skeletal muscle. ATP‐mediated vasodilation and exercise hyperemia are dependent, in part, on activation of inwardly rectifying potassium (KIR) channels and subsequent smooth muscle cell hyperpolarization, with a modest reliance on the production of nitric oxide (NO) and prostaglandins (PGs). However, recent studies from our laboratory indicate that these pathways are not obligatory for contracting skeletal muscle to blunt α1‐adrenergic vasoconstriction. Given the specific role of KIR channels in ATP‐mediated vasodilation, the primary purpose of this study was to determine whether the ability of ATP to blunt α1‐adrenergic vasoconstriction is dependent upon KIR channel activity in humans. A secondary purpose was to determine whether the ability of ATP to blunt α1‐adrenergic vasoconstriction is dependent upon activation of KIR channels and Na+/K+‐ATPase, as well as the synthesis of NO and PGs. In a total of 13 young subjects we measured forearm blood flow (Doppler ultrasound) and calculated changes in vascular conductance (FVC) to local intra‐arterial infusion of phenylephrine (PE; α1‐agonist) during infusion of ATP or a control vasodilator(s) (Protocol 1 (n=7): adenosine (ADO), and sodium nitroprusside (SNP); Protocol 2 (n=6): ADO). Vasomotor responses were assessed before and after blockade of signaling pathways that contribute to ATP‐mediated vasodilation (Protocol 1: KIR channels (barium chloride); Protocol 2: combined blockade of KIR channels, Na+/K+‐ATPase (ouabain), NO (L‐NMMA), PGs (Ketorolac)). Protocol 1: ATP significantly attenuated PE‐mediated vasoconstriction relative to both SNP and ADO (Δ FVC: ATP: −16 ± 2; ADO: −38 ± 6; SNP: −59 ± 6%; P<0.05 vs ADO and SNP). Blockade of KIR channels significantly attenuated ATP mediated vasodilation ~40% (P<0.05 vs. control), but had no effect on the ability of ATP to blunt PE‐ mediated vasoconstriction (Δ FVC: −6 ± 5%; P>0.05 vs. control). Protocol 2: Despite combined blockade of KIR, Na+/K+‐ATPase, NO, and PGs resulting in profound attenuation of ATP‐mediated vasodilation (−~60%; P<0.01 vs. control), ATP was still able to blunt PE‐mediated vasoconstriction (Δ FVC: −4 ± 14%; P=0.50 vs. control). Together these studies highlight that while NO, PGs, and vascular smooth muscle hyperpolarization (via KIR channel activation) are contributors to the normal vasodilatory response to exercise and exogenous ATP, these pathways are not obligatory for exercise or ATP to blunt α1‐adrenergic vasoconstriction in humans.Support or Funding InformationSupport: HL119337, HL095573
ARMAX‐based Method Extends Knowledge of the Baroreflex
Authors: Lund Morten Toft , Salomonsson Max , Jonassen Thomas EN , von Holstein‐Rathlou Niels‐Henrik 
Published: November 2023

IntroductionThe arterial baroreceptor‐heart rate reflex (baroreflex) is a key mechanism in regulating the cardiovascular system, and alterations in baroreceptor function are seen in many disease states, including heart failure, obesity and hypertension. Recent studies have identified impairment of the baroreflex early in the clinical course of hypertension. We propose a new and simple method for analyzing these alterations in baroreceptor function. The method is validated to describe dynamic relationships in causal systems with feedback, and in addition to the traditional estimate of baroreflex sensitivity (BRS) it adds information on two new valuable components of the reflex. Firstly, the average time for the baroreflex to reach its maximal effect on heart rate (HR) following a change in blood pressure (BP), and secondly, the average maximal change in HR produced by the baroreflex. This study aims to validate the method against a traditional method of estimating BRS in both healthy animals and in a verified model of diet‐induced obesity and hypertension.Methods48‐hour data series of continuous BP and HR recordings were collected with telemetry and used for analysis. 16‐weeks‐old SD rats on standard chow (n=11) served as healthy controls, while a similar group of rats on a high‐fat, high‐fructose (HFHC) diet from 4 weeks of age (n=6) constituted the obese hypertension model. An Autoregressive–moving‐average model with exogenous inputs (ARMAX)‐based algorithm was applied to the data series and compared with the α‐coefficient.ResultsThe ARMAX‐based method matched the traditional method, and interestingly when comparing the obese hypertension group with controls (body weight 531±27 vs. 458±19 g, p<0.05; mean arterial pressure 119±3 vs. 102±1 mmHg, p<0.05) the same degree of attenuation in BRS of ~50 % could be observed in the obese hypertensive group compared with controls with both methods (ARMAX: −0.08±0.01 vs. −0.15±0.01 Δbpm/heartbeat, p<0.05; α‐coefficient: 0.51±0.07 vs. 0.89±0.07 ms/mmHg, p<0.05). The ARMAX‐based method additionally demonstrated the maximal change in HR following a BP change to be reduced by ~50 % in the obese hypertensive group compared with controls (1.3±0.2 vs. −2.6±0.2 Δbpm, p<0.05), while the time until the maximal change in HR was reached was similar between groups.ConclusionThe ARMAX‐based method confirms traditional methods and presents an unbiased method of characterizing HR changes in response to changes in BP. The method further contributes to our understanding of the reflex by providing information on time to maximal change in HR as well as the degree of maximal change in HR. The presented algorithm can potentially be applied to other species including humans.Support or Funding InformationPregraduate Research Scholarship from The Danish Council for Independent Research, Grant from Fru Ruth König Petersens Foundation, Helge Peetz and Verner Peetz and Hustrus Scholarship.
Sleep Apnea Worsens Muscle Vasoconstriction During Central and Peripheral Chemoreceptors Stimulation in Patients with Systolic Heart Failure
Authors: Lobo Denise M L , Trevizan Patricia F , Toschi‐Dias Edgar , Oliveira Patricia A , Piveta Rafael B , Mady Charles , Bocchi Edimar A , Almeida Dirceu R , Lorenzi‐Filho Geraldo , Middlekauff Holly R , Negrão Carlos E 
Published: November 2023

We tested the hypothesis that muscle vasoconstriction in response to hypercapnia and hypoxia would be more pronounced in patients with chronic heart failure (CHF) and sleep apnea than patients with CHF alone. Ninety consecutive CHF patients, Functional Class II‐III NYHA, LVEF≤40% were selected to the study. Forty‐two patients who fulfilled all the inclusion criteria were enrolled in the study: No Sleep Disordered Breathing (NoSDB, n=13, 47±3y), Obstructive Sleep Apnea (OSA, n=22, 57±1y) and Central Sleep Apnea (CSA, n=07, 53±3y). Sleep apnea was characterized by apnea‐hypopnea index≥15 events/hour (polysomnography). Central (7%CO2 and 93%O2) and peripheral (10%O2 and 90%N2, with CO2 titrated) chemoreceptors were stimulated for 3 min. Muscle sympathetic nervous activity (MSNA) was evaluated by microneurography technique, forearm (FBF) and calf (CBF) blood flow by venous occlusion plethysmography, and blood pressure by beat‐to‐beat noninvasive technique. Baseline MSNA, FBF, forearm vascular conductance (FVC), CBF, and calf vascular conductance (CVC) were similar among groups. FBF (hypercapnia: P=0.001; and hypoxia: P=<0.001) and CBF (hypercapnia: P=<0.001; and hypoxia: P=0.002) responses were significantly lower in OSA and CSA groups compared to NoSDB group. FVC (hypercapnia: P=0.001; and hypoxia: P=<0.001) and CVC (hypercapnia: P=<0.001; and hypoxia: P=0.001) responses were also significantly lower in OSA and CSA groups compared to NoSDB group. MSNA responses were not different in all groups studied (hypercapnia: P=0.12; and hypoxia: P=0.17). Patients with CHF and obstructive or central sleep apnea have more severe muscle vasoconstriction during hypercapnia and hypoxia than patients with CHF alone. The similarities in MSNA suggest that these responses are associated with endothelial dysfunction.Support or Funding InformationCNPq #140265/2013‐9 and FAPESP #2010/50048‐1
High Salt Challenge Augments Expression of Proinflammatory Cytokines and Contributes to Elevated Neuronal Activity in the Hypothalamic Paraventricular Nucleus
Authors: Zhu Fengli , Larson Robert A , Shi Peng , Li Ningjun , Chen Qinghui , Shan Zhiying 
Published: November 2023

Previous studies have demonstrated that brain proinflammatory cytokines (PIC) play an important role in neurogenic hypertension. However, little is known about the role of brain inflammation in salt sensitive hypertension (SSHTN). In this study, we tested the hypothesis that the PIC expression is increased in the hypothalamic paraventricular nucleus (PVN) and contributes to increased neuronal activity in SSHTN. To test this hypothesis, 8‐week‐old Dahl salt sensitive (DS) rats were divided into two groups (n=3~ 5/group) and fed with either a high salt (HS, 4% NaCI) or normal salt (NS, 0.4% NaCl) diet. Four weeks following diet treatment, rats were euthanized, the PVN was punched out, and real time PCR were performed to assay genes of interest. HS treatment resulted in respective 8 fold, 4 fold, and 7 fold increases in TNFα, IL1β and IL6 mRNA levels in the PVN. In addition, Fra1, a chronic neuronal activation marker, was also increased by 4 fold. Additionally, in order to examine the action of acute hypertonic NaCI on the expression of PIC and neuronal activation marker, adult male SD rats were divided into two groups (n=3~4 per group) and received intracerbroventricular infusion of either hypertonic (2M, 2μl), or isotonic (0.15 M, 2μl) NaCI under anesthetized condition. Three hours following the infusion, rats were euthanized and PVN mRNA levels of PIC and Fra1 assayed. Results indicate that hypertonic saline infusion induced significant increases in mRNA levels of PIC including TNFα (6‐fold), IL1β (13‐fold) and IL6 (21‐fold), as well as neuronal activation marker Fra1 (8‐fold). Finally, we tested whether or not the increase in PIC expression occurred in neurons. Incubation of hypertonic saline (10 mM NaCI plus full medium) for 3 hours resulted in a 12‐fold increase in IL6 and 2.8 fold increase in Fra1 mRNA levels in neuronal cultures from the hypothalamus containing the PVN of neonatal SD rats. These observations suggest that HS intake induced inflammation in the PVN may contribute to increased sympathetic nerve activity and therefore to SSHTN developmentSupport or Funding InformationFunding support: AHA 11SDG7420029, Zhiying Shan; R15‐HL122952, Qinghui Chen
Central Anti‐inflammatory and Neuronal Effects of Butyrate in Wistar Kyoto and Spontaneously Hypertensive Rats
Authors: Yang Tao , Rodriguez Vermali , Colon‐Perez Luis , Redler Ty , Febo Marcelo , Sumners Colin , Zubcevic Jasenka 
Published: November 2023

IntroductionEmerging evidence demonstrates a significant link between gut dysbiosis and hypertension (HTN). Recently, we observed a reduction in the butyrate‐producing bacteria in the gut of spontaneously hypertensive rats (SHR) compared to Wistar Kyoto (WKY) control, suggesting reduced butyrate availability in HTN. Butyrate, one of the major fermented end‐products of gut microbiota, reportedly produces beneficial effects in multiple dysbiosis‐related diseases, partly through its role in the regulation of inflammatory responses. Considering the established link between neuroinflammation and HTN, we hypothesized that some of the beneficial effects of butyrate may be via a central regulatory mechanism.MethodsIn situ rat preparation was used to test the effects of systemic butyrate application (500mg/kg in sterile saline) in juvenile SHR and control rats (4 weeks old). WKY and SHR primary astrocytes from two days old pups were cultured in DMEM, supplemented with 10% FBS and 1% pen/strep, for 14 days, prior to treatment with 1mM butyrate for 4 hours. Cells were collected for real time PCR analysis. Total RNA was isolated from the PVN region of 8 WKY and 8 SHR rats (12–14 weeks old) for real time PCR analysis of inflammatory factors. For functional magnetic resonance imaging (fMRI), adult WKY and SHR rats were briefly anaesthetized with 4% Isoflurane, and kept at 1.0%–1.5% during imaging. ICV catheters were implanted in all rats using the established Paxinos‐Watson coordinates. Images were collected prior to and immediately after a single butyrate injection (100 ng in aCSF), on an actively shielded 470MHz (4.7T‐Tesla) Magnex Scientific MR scanner controlled by Agilent Technologies VnmrJ 3.1 console software.ResultsSystemic application of 500 mg/kg butyrate produced an immediate reduction in BP in normotensive controls (Δ=18±1 mmHg). This effect of butyrate on BP was modestly but significantly lower in the juvenile SHR (Δ=12±1 mmHg, P<0.05, n=3 per group). Real time PCR revealed a ~56% reduction in expression of the butyrate‐sensing olfactory receptor (Olfr) 59 in the hypothalamus of SHR compared with WKY. In line with this, fMRI demonstrated reduced brainstem neuronal activation (by~40%) in the SHR compared to the WKY following a single ICV injection of butyrate (n=3 per group). In addition, butyrate treatment significantly lowered expression levels of Ccl2 (by 33 %, P value= 0.0082) and Tlr4 (by 48 %, P value =0.01) in the primary astrocyte culture from the SHR.ConclusionButyrate reduced inflammatory mediators in the SHR astrocytes in vitro, and produced lower effects on the neural activation and BP in the SHR, possibly due to decreased expression of Olfr59. Therefore, effects of butyrate may also be mediated via a central regulatory mechanism.Support or Funding InformationAHA 14SDG18300010;UF College of Veterinary Medicine