bluuebunny/crossref_metadata_2025_split huggingface dataset:
Independent and Pleiotropic Gene Effects on Hypertension and Metabolic Syndrome in Lyon Hypertensive Rats
Authors: Kwitek Anne E , Pettus Janette M , Jakoubek Jessica A , Ma Man Chun John 
Published: November 2023

The Lyon Hypertensive (LH) rat is an inbred selection model of spontaneous hypertension. However through the selection and inbreeding of the LH strain for high blood pressure, genes causing salt‐sensitivity and several features of the Metabolic Syndrome (MetS) including obesity and dyslipidemia were also fixed; thus the LH rat is a genetic model of MetS associated hypertension. Conversely, the Lyon Normotensive (LN) control strain is normotensive, salt‐resistant and displays no features of MetS. Both strains were selectively bred from the same outbred Sprague Dawley founders, based on divergent blood pressures, yet their genomes are >99.98% identical. Our overall goal is to identify novel genes and pathways linking disparate phenotypes in MetS. We performed comprehensive systems genetic studies in LH rats and determined that rat chromosome (RNO) 17 contributes not only hypertension but also obesity and dyslipidemia. Genetic mapping studies identified overlapping quantitative trait loci (QTL) for blood pressure, body weight, and plasma lipids on RNO17 in the LH rat. Whole genome sequencing of LH and LN strains revealed large blocks of RNO17 are of shared ancestry; haplotype fine‐mapping refined a list of 26 candidate causal genes. Consomic and congenic studies determined that the whole chromosome substitution of LH RNO17 with that of the LN was sufficient to reduce blood pressure, lipid levels, and body weight. Interestingly, a congenic strain substituting only the distal end of LH RNO17 with the LN allele reduces blood pressure and serum lipids independent of body weight, suggesting both independent and pleiotropic gene effects in LH hypertension. We used RNA‐seq to identify transcriptome differences between LH and LN strains, and to map genetic regulation of gene expression (eQTL). Proximal RNO17 was found to regulate the expression of over 60 genes located elsewhere in the genome (a trans‐eQTL hotspot). A single candidate gene in this locus (RGD1562963), is cis‐regulated, has sequence variation between LH and LN rats, is differentially expressed in multiple tissues between LH and LN, and controls the expression of downstream genes mapping to the trans‐eQTL hotspot that are associated with hypertension and MetS. Our integrative studies suggest that genetic variation in LH RNO17 has independent and pleiotropic effects on hypertension and features of MetS.Support or Funding InformationThis work is supported by NIH grants R01HL089895 and R21DK089417, AHA grant 14GRNT20410043, and the Fraternal Order of Eagles Diabetes Research Center at the University of Iowa.
The Hypercapnic Ventilatory Response and Behavior in Ca2+‐activated K+ (BK) Channel knock Out Mice
Authors: Putnam Robert W , Patrone Luis G.A. , Ratliff Christine A. , Gargaglioni Luciane H. 
Published: November 2023

In locus coeruleus (LC) neurons, the firing rate response of CO2/pH chemosensitive neurons has been suggested to be modulated by the activity of BK channels. Hypercapnic acidosis (HA) activates Ca2+ channels which lead to increased intracellular Ca2+ and activation of BK channels. When BK channels are inhibited, the firing rate response to HA increases (Imber et al. 2014. Biochim. Biophys. Acta 1842:2569–2578). In the current study, we examined the hypercapnic ventilatory response in mice with the BK channel knocked out (BK KO mice). We also studied the firing rate response of LC neurons to hypercapnia in wild type (WT) and BK KO mice. Finally, we studied the phenotype of these mice with respect to overall locomotion and anxiety responses. Elevated inspired CO2 (7%) reversibly increased ventilation in both WT and KO mice (increase about 3 fold in WT, n=8, and 4–5 fold in KO mice, n=6; P<0.05). The increased ventilation was due to increased tidal volume and respiratory frequency in both WT and KO mice, but the larger ventilatory increase induced by inspired CO2 in KO vs. WT mice was entirely due to a larger tidal volume response. Hypercapnia‐induced increases in ventilation were not due to increased metabolism, which was the same in both WT and KO mice in normocapnia and in hypercapnia (about 5 ml/100g‐min). The firing rate response to 10% CO2 (from a control level of 5% CO2) increased about 74% (from 0.42–0.73 Hz) in LC neurons from male WT mice while it increased by greater than 3 fold (from 0.30–1.26 Hz) in LC neurons from male BK KO mice. BK KO mice showed an increased activity level and an unusual hopping behavior compared to WT mice. When total distance traveled and average velocity were measured over a 30 minute period, BK mice showed significantly greater distance traveled (P<0.02; n=6) and faster average velocity (P<0.02; n=6) compared to WT mice. However, at room air there was no evidence for anxiety behavior in the performance of BK mice in either the open field test or the elevated plus maze test. Our data show that the lack of a BK channel in LC neurons from mice results in increased firing rate in response to hypercapnia. Further, the lack of BK channels in KO mice leads to an increased hypercapnic ventilatory response. These findings support the hypothesis that BK channels act as a brake on the hypercapnic response of chemosensitive neurons. Our findings also suggest that there is an activity phenotype in BK KO mice although we find no evidence of increased anxiety, at least under normocapnic conditions, in BK KO mice.Support or Funding InformationSupported by a Wright State University Emerging Science Seed Grant (to RWP) and CNPq and Fapesp grants (to LGAP and LHG).
Effects Of 5‐HT2A And 5‐HT7 Receptors In The RTN Region On Breathing During Eupnea And Hypercapnia
Authors: Muere Clarissa , Hodges Matthew 
Published: November 2023

Raphé‐derived neuromodulators, such as serotonin (5‐HT), increase the excitability of many neurons, including Phox2b‐expressing retrotrapezoid nucleus (RTN) neurons. Here, we sought to test the hypothesis that unilateral blockade of 5‐HT receptors in the RTN region will decrease ventilation at rest and during hypercapnia. We chronically implanted guide cannulae targeting the RTN in Sprague‐Dawley (SD, n=2) and Dahl salt‐sensitive (SS, n=2) rats. After >7 days recovery, we inserted a probe for reverse microdialysis of mock cerebrospinal fluid (mCSF) and serotonergic receptor antagonists, while measuring breathing in room air and in 7% CO2 in unrestrained, conscious animals. Preliminary results show that dialysis of the 5‐HT2A receptor antagonist, MDL 11,939 (20 μM), consistently reduced eupneic (−19 ± 2%) and CO2 breathing (−29 ± 5%) compared with control conditions (dialysis of mCSF alone) in SS rats. Furthermore, dialysis of MDL 11,939 consistently reduced eupneic breathing (−37 ± 16%) and had mixed effects on CO2 breathing (−20 ± 25%) in SD rats. Dialysis of the 5‐HT7 receptor antagonist, SB258719 (100 μM), reduced eupneic breathing (−11.2 to −43%) and enhanced the CO2 chemoreflex (+65 to +248%) in one rat from each strain. Combined dialysis of MDL 11,939 and SB258719 in these same rats, however, reduced eupneic (−34 ± 8%) and CO2 breathing (−26 ± 10%) compared with control conditions. Thus, unilateral blockade of 5‐HT2A receptors, 5‐HT7 receptors, or both consistently decreases eupneic ventilation, but has mixed effects on the CO2 chemoreflex. These data suggest that 5‐HT2A and 5‐HT7 receptors in the RTN may modulate breathing at rest and during hypercapnia in vivo.Support or Funding InformationThis study was supported by National Institutes of Health grant HL122358.
Orexin 1 Receptors Are necessary for Phase‐Specific Enhancement of The Hypercapnic Ventilatory Response in Female Rats Subjected to Neonatal Stress
Authors: Lopes Luana Tenorio , Gulemetova Roumiana , Drolet Guy , Bretzner Frédéric , Kinkead Richard 
Published: November 2023

Panic disorder (PD) is an anxiety disorder that affects ~3 times more women than men. Respiratory manifestations of PD appear after puberty and include an increased sensitivity to CO2. This observation suggests that ovarian function contributes to the onset of PD. In humans and rodents, exposure to stress during early life alters brain development and is considerate a risk factor for PD. Using Neonatal Maternal Separation (NMS) as a stressor, we showed that NMS augments the ventilatory response to CO2 in adult female rats but these effects are not present in pre‐pubertal rats. Based on these observations we first tested the hypothesis that cyclic hormone fluctuations influence chemosensitivity. In addition to their involvement in fear and vigilance responses, orexin neurons (ORX) are CO2 sensitive. Based on these properties, ORX has been linked to PD. Thus, we also tested the hypothesis that ORX receptors are necessary for stress‐related enhancement of the CO2 response.Pups subjected to NMS were placed in an incubator for 3 h/day from postnatal day 3 to 12. Control pups remained undisturbed. Female rats were reared until adulthood (P60–70), and the ventilatory response to CO2 was measured by whole‐body plethysmography (FICO2 = 0.05, for 10 min). OX1 antagonist (SB334867; 15mg/kg) or vehicle (ip) was injected 45 to 60 minutes before start the recordings. After the experiment, the oestrus cycle was verified by vaginal smear.In controls, the ventilatory response to CO2 did not change across the estrus cycle. The hypercapnic ventilatory response of NMS females was phase‐dependent with the greatest responsiveness observed during proestrus. Pharmacological inactivation of OX1 receptors had not effect on the hypercapnic response of controls, but reduces the respiratory response to CO2 in NMS females, the most important effects were observed during proestrus and metaestrus phases.Based on the phase‐dependent increase in NMS females, we conclude that stress interferes with the influence that sex‐hormones exert on respiratory control. These effects may take place in the hypothalamic region that contain ORX neurons since activation of OX1 receptors are necessary for stress‐related enhancement of the hypercapnic ventilatory response. These results provide new insight into the pathophysiology of PD.Support or Funding InformationCanadian Institutes of Health Research and CNPq ‐ Brazil.
Role of central serotonin in sleep architecture and arousal in infant rat pups
Authors: Young Jacob , Hodges Mathew , Cummings Kevin 
Published: November 2023

Sudden Infant Death Syndrome (SIDS) occurs during sleep and is the leading cause of infant death in the post‐neonatal period. SIDS cases have more active sleep (AS), a sleep state associated with apnea and cardiovascular instabilities. It is also thought that SIDS involves a failure to arouse from an apneic event during sleep. Defects within the brainstem serotonin (5‐hydroxytryptamine, 5‐HT) system (including a loss of 5‐HT content) are associated with SIDS, and a causal role 5‐HT deficiency is suggested by recent studies using rodents deficient in central 5‐HT. However, how a specific loss of central 5‐HT in neonatal life affects sleep, respiratory control across sleep states and arousal from sleep has not been investigated. We hypothesized that 5‐HT deficiency increases the amount of active sleep (AS), compromises breathing mostly during quiet sleep (QS) when 5‐HT neurons still fire, and blunts the arousal response to hypercapnia. We monitored sleep and breathing over ~2hrs in two groups of unanaesthetized, 2 week‐old rat pups deficient in tryptophan hydroxylase‐2 (TPH2−/−) and wild‐type controls (WT). One group (n=6 WT, 5 TPH2−/−) was kept in normoxic conditions and the other group (n=10 WT, 8 TPH2−/−) was given intermittent challenges of 5% CO2 at the beginning of episodes of AS and QS until arousal. Sleep state was determined using nuchal electromyography and behavioral observation. Breathing was monitored using whole body plethysmography. We measured the duration of AS and QS episodes (i.e. latency to arousal) in normocapnia and hypercapnia, and in normocapnia measured respiratory variables in each sleep state: frequency (fB), tidal volume (VT), ventilation (VE) and the co‐efficient of variation of the respiratory period (CV%). While the duration of QS episodes was not influenced by 5‐HT deficiency, TPH2−/− pups experienced episodes of AS that were ~2‐times longer than those of controls (~190 vs 90 sec; p=0.003). In AS, hypercapnia had no effect on the latency to arousal of either WT or TPH2−/− pups. In QS, hypercapnia reduced the arousal latencies of WT pups (from ~108 sec to 72 sec), but had no influence on the latencies of TPH2−/− pups (state × gas × genotype: p=0.02). 5‐HT deficiency significantly reduced fB and VE in both sleep states (p<0.001 for both). Breathing stability was significantly compromised by 5‐HT deficiency, but only in AS (genotype × state: p<0.001). We conclude that at an age close to infancy, central 5‐HT deficiency increases the duration of AS episodes, destabilizes breathing during AS, and delays arousal from hypercapnia during QS. These findings lend support the hypothesis that reduced 5‐HT signaling alters sleep architecture and breathing in a way that increases SIDS risk.Support or Funding InformationFunding for this research was provided by the American Physiological Society Undergraduate Student Research Fellowship Program (to J.Y.) and by an American Heart Association Scientist Development Grant (14SDG18560022; PI: KJC).
Role of central serotonin (5‐HT) in sleep architecture and the control of breathing during sleep in adult rats
Authors: Magnusson Jennifer , Li Aihua , Hodges Mathew , Cummings Kevin 
Published: November 2023

5‐HT neurons have a relatively high firing frequency during wakefulness (QW), a reduced firing rate during quiet sleep (SWS), and are essentially quiescent during rapid eye movement sleep (REMS). Studies have shown that mice lacking tryptophan hydroxylase 2 (TPH2), the rate limiting enzyme in central 5‐HT synthesis, have a reduced arterial blood pressure (BP) and breathing frequency (fB). However, the specific role of brainstem 5‐HT in sleep architecture and cardiorespiratory regulation across sleep states is unclear. We hypothesized that, relative to control littermates, TPH2‐deficient adult rats (TPH2−/−) would have increased sleep, and that during QW and QS they would have reduced arterial blood pressure (BP), fB and ventilation (VE) and a destabilized respiratory pattern relative to controls. To test these hypotheses, we used electroencephalography and electromyography to monitor the sleep state of adult rats deficient in tryptophan hydroxylase 2 (TPH2−/−; n=17) and littermate controls (TPH2+/+; n=13). Femoral arterial catheters were used to measure BP and heart rate (HR), and whole body plethysmography was used to measure respiratory variables, including fB, tidal volume (VT), ventilation (VE), and metabolic rate (VO2). We also measured the coefficient of variability in breathing (CV%) as an index of respiratory stability. TPH2−/− rats experienced episodes of REMS and SWS that, on average, were ~110s and ~40s longer than controls, respectively (p<0.0001 and p=0.028, respectively). 5‐HT deficiency had no effect on BP or HR in any sleep‐state. A loss of central 5‐HT reduced breathing fB in REM sleep (10 bpm; p<0.001), but not in QW or QS. TPH2−/− rats had a significantly increased VT compared to controls (~0.0015ml/g ; p=0.013) but, contrary to our hypothesis, genotype had no significant effect on VE or VE/VO2 in any state. However, across all states female TPH2−/− rats displayed a significantly destabilized breathing pattern compared to female TPH2+/+ (p=0.003). In summary, our data suggest that central 5‐HT signaling regulates the duration of REM sleep as well as the respiratory rhythm and pattern during REM sleep.Support or Funding InformationFunding for this research was provided by an American Heart Association Scientist Development Grant (14SDG18560022; PI: KJC).
Caffeine improves survival in autoresuscitation‐impaired serotonin deficient rats
Authors: Lee Stella , Nattie Eugene 
Published: November 2023

Our previous investigation demonstrated that an existing underlying vulnerability in rat neonates (i.e. brainstem 5‐HT deficiency) in combination with a stressor (i.e. pre‐ and early post‐natal nicotine exposure) exacerbates autoresuscitation failure from an anoxic event at a critical developmental period (P10 rats). During this critical period, we hypothesize that caffeine, a respiratory stimulant, will improve successful autoresuscitation rates in the 5‐HT deficient, nicotine exposed P10 neonates and reduce mortality. Preliminary data demonstrate that an intraperitoneal injection of 10mg kg−1 caffeine prior to anoxic challenge improves autoresuscitation rates (survival rate approximately 40%) in the 5‐HT deficient, nicotine exposed P10 rats in comparison to the rats who received IP saline vehicle injections (survival rate of 25%). Prior investigation suggests that eupnea and heart rate recovery following an anoxic event (which elicits an apnea accompanied by a bradycardia) is significantly delayed in 5‐HT deficient rats treated with nicotine, making them more susceptible to failure of autoresuscitation (p<0.05). Presence of caffeine is likely facilitating successful autoresuscitation by shortening apnea duration and promoting an early onset of gasping post‐apnea for a faster eupnea and heart rate recovery.Support or Funding InformationResearch is supported by the NIH Program Project Grant HD036379 (NICHD, PI, Dymecki, S. M.; Project PI, Nattie, E. E.). The authors would also like to acknowledge the generous support of the Tenney Fund and the Ryan Fellowship (awarded to S. Lee).
New Theory of Holistic Integrative Physiology and Medicine IV: Fetus Does Not Breathing and How We Start It After Birth
Authors: Sun Xing‐Guo 
Published: November 2023

ObjectiveThe fetus does not have any true breathing. After birth, we have to start breathing and breathing is our vital sign for life before we expired. Just the short period before and after birth we should have the same system and same mechanism of breathing control. However, the knowledge of traditional respiratory systemic physiology could not explain these clearly. Based on new constructed HOLISTIC INTEGRATIVE PHYSIOLOGY AND MEDICINE, we explained how we control our breathing after birth (see II abstract), but we did not talk about those before birth and short period after birth.MethodsNow we plan to use the different arterial blood gas signals (trinity of PO2, PCO2 and [H+]) at different time period to discuss mechanisms of why fetus no breathing and how we start our first breathing after birth.ResultsWhy fetus does not need breathing? Mother is normal breathing with mean PaO2=~100mmHg, PaCO2=~40mmHg and pHa=~7.40 of up‐down waveform in artery as described in II abstract. The fetus obtains oxygen and nutrients from the mother through the placenta and the umbilical cord. When the uterus arterial blood goes through the placenta capillary, the magnitude of waveform in umbilical vein decreases, and then the blood pass through PFO from RA into LA was diluted more than 10 times by venous return blood, so that mean PfO2=~30mmHg, PfCO2=~45mmHg and pHf=~7.38 in fetus artery without up‐down waveform. Even if they are very low O2, high CO2 and [H+]; the stable mean levels of them do not change the stimulation via peripheral chemical receptors and nerve net. So fetus does not have any true breathing.How we start our first breathing after birth? After birth, newborn's cell is metabolic and circulation is running, so that before breathing its arterial blood gases will go to much lower O2 and higher CO2 and [H+], progressively. The newborn mean are PaO2=6–30mmHg, PaCO2=42–66mmHg and pHa=7.18–7.38, before first breathe. While the PaO2, PaCO2 and pHa reach some threshold, the stimulation via peripheral chemical receptors and nerve net to start our first breathing. The mind is meaning that “we are air hunger, do we breathe or die? After our first breathing started, we breathing by arterial blood gases up‐down signals switching ins‐ and expiration via peripheral chemical receptors and nerve net; and maintaining stability via central chemical receptors and nerve net (see II abstract).ConclusionWe can explain the mechanisms of stable arterial blood gases (none waveform) in fetus does not need any true breathing, and after birth, the decreasing of O2 and increasing of CO2 and [H+] will start our first breathing via chemical receptors and nerve net. Based on it, we also explain some existing questions in physiology of respiration and circulation: How we set of FRC and why we close our PFO after birth etc. in different abstracts.Support or Funding InformationCNSF‐Medical Science Program (81470204); NCCVD Fuwai Hospital Start Program (2012‐YJR02)
Hypoxia Reduces HUWE1 by Downregulating PPARγ in Mouse Lungs and Human Pulmonary Artery Endothelial Cells
Authors: Kang Bum‐Yong , Kleinhenz Jennifer M , Murphy Tamara C , Sutliff Roy L , Hart C Michael 
Published: November 2023

RationalePulmonary hypertension (PH) causes significant morbidity and mortality. Hypoxia is an important mediator in the pathogenesis of PH. We recently reported that the peroxisome proliferator‐activated receptor gamma (PPARγ) ligand, rosiglitazone (RSG), attenuates hypoxia‐induced: a) increases in nuclear factor kappa‐B p65 (NF‐κB p65) activation and b) decreases in lung microRNA‐98 (miR‐98) levels.ObjectiveWe hypothesized that reductions in PPARγ reduce levels of a homology to E6‐AP C terminus E3 ubiquitin ligase (HUWE1), an E3 ubiquitin ligase and host gene of miR‐98, leading to increased NF‐κB p65 expression in hypoxia‐induced PH.Methods and ResultsMale C57BL/6 mice were exposed to hypoxia (10% O2) or normoxia (21% O2) for 3 weeks. Hypoxia reduced HUWE1 levels in mouse lungs. In contrast, in mice treated with RSG (10 mg/kg/d by gavage) for 10 days, RSG attenuated reductions in HUWE1 in mouse lung. In vitro, human pulmonary artery endothelial cells (HPAECs) were exposed to hypoxia (1% O2) or normoxia (21% O2) for 72 hours. Hypoxia reduced HUWE1 expression. These alterations were attenuated by treatment with RSG (10 μM) during the last 24 hours of hypoxia exposure. Loss of PPARγ function reduced HUWE1 levels and gain of PPARγ function increased HUWE1 levels in vivo and in vitro. Furthermore, while knockdown of NF‐κB p65 does not regulate HUWE1 levels, the depletion of HUWE1 increases NF‐κB p65 levels. These novel findings are consistent with the postulate that PPARγ increases HUWE1 to induce ubiquitination of p65 and termination of NF‐κB signaling.ConclusionCollectively, these findings suggest that PPARγ attenuates hypoxia‐induced reductions in HUWE1 levels by inhibiting activation of hypoxia‐responsive transcription factors, such as NF‐κB p65. Targeting PPARγ represents a novel therapeutic strategy to inhibit NF‐κB p65 that contributes to PH pathogenesis.Support or Funding InformationSupported by Atlanta VA Merit Review 1I01BX001910, NIH HL 102167 (RLS and CMH), AHA‐SDG 13SDG14150004 (BYK).