bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibiting Cyclooxygenase Activity Attenuates the Exaggerated Exercise Pressor Reflex in Male UCD-Type 2 Diabetes Mellitus Rats
Authors: Samora Milena , Huo Yu , Graham James , Stanhope Kimber , Havel Peter , Harrison Michelle , Stone Audrey
Published: May 2023

It is well established that prostaglandins, a product of cyclooxygenase (COX) enzymes contribute to evoking the exercise pressor reflex. Previous studies suggest that COX expression is upregulated in the peripheral nerves of those with type 2 diabetes (T2D), likely due to low grade inflammation associated with the disease. The purpose of this study was to determine if COX activity in the exercising skeletal muscle exaggerates the exercise pressor reflex in T2D. We hypothesized that inhibiting COX activity in the hindlimb would reduce the exaggerated pressor response to muscle contraction in T2D rats. To do this, we evoked the exercise pressor reflex by statically contracting the skeletal muscle for 30s in unanesthetized, decerebrate rats. Experiments were performed on male University of California Davis (UCD)-T2D (n=8; body weight: 526 ± 42g) and Sprague Dawley rats (n=3; body weight: 473 ± 10g). Changes (Δ) in peak mean arterial pressure (MAP) and heart rate (HR) responses to exercise were compared before and after locally injecting indomethacin (1 mg/kg in 0.2 mL of 100 mM sodium carbonate), a COX 1 and 2 inhibitor, or its vehicle (0.2 mL of 100 mM sodium carbonate) into the arterial supply of the ipsilateral (contracting) and contralateral (non-contracting) hindlimb. Data are presented as mean ± SD. We found that local injection of indomethacin into the contracting hindlimb reduced the exaggerated peak pressor (ΔMAP: 30 ± 14 mmHg to 18 ± 8 mmHg; P<0.01) but not cardioaccelerator (ΔHR: 21 ± 8 bpm to 19 ± 11 bpm; P=0.59) responses in T2D rats, but did not reduce these responses in healthy rats (ΔMAP 14 ± 3 mmHg to 14 ± 6 mmHg; P>0.99; ΔHR: 10 ± 5 bpm to 13 ± 7 bpm; P=0.67). Conversely, local injection of indomethacin into the non-contracting hindlimb (n=4), as well as injection of the vehicle in the contracting hindlimb (n=4), did not affect the pressor response to muscle contraction in T2D rats. Developed tensions during muscle contraction were similar for all comparisons. In summary, our findings suggest that COX activity contributes to the exaggerated pressor response to muscle contraction in T2D rats. This project was supported by NIH R01 HL144723.

This project was supported by NIH R01 HL144723.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Visfatin-Induced Smooth Muscle Cell Stiffness Syndrome during Lysosomal Acid Ceramidase Deficiency
Authors: Li Guangbi , Zhang Fan , Huang Dandan , Zou Yao , Li Pin-Lan
Published: May 2023

Recent studies have reported that intrinsic stiffness of smooth muscle cells (SMCs) plays an important role in contributing to arterial wall stiffness, which led to the concept of smooth muscle cell stiffness syndrome (SMCSS). However, the molecular mechanisms regulating the intrinsic stiffness of SMCs are still poorly understood. The present study tested whether lysosomal acid ceramidase (AC) determines intrinsic stiffness of mouse aortic SMCs via regulation of actin polymerization and integrin recycling. Atom force microscopy was used to study mechanical properties of SMCs. As an injurious adipokine, visfatin was found to reduce SMC height, but elevate cortical stiffness and focal adhesion in SMCs, indicating the augmentation of intrinsic stiffness. Moreover, visfatin-induced elevation of cortical stiffness was associated with increased actin polymerization in peripheral areas of SMCs. These pathological changes were much more remarkable in SMCs from smooth muscle-specific Asah1 gene (gene code of AC) knockout (Asah1fl/fl/SMcre) mice compared to SMCs from WT/WT mice. Super-resolution microscopy showed that multivesicular bodies (MVBs) as integrin degrading organelles were much less interacted or fused with lysosomes in SMCs from Asah1fl/fl/SMcre mice than WT/WT mice upon visfatin stimulation. In contrast, MVB-α5 integrin encounters increased more in SMCs from Asah1fl/fl/SMcre mice compared to SMCs from control littermates, suggesting that AC deficiency increases α5 integrin accumulation in MVB, which may enhance recycling endosome moving to cell membrane. Given the vital role of lysosomal transient receptor potential mucolipin 1 (TRPML1) channel in the regulation of lysosome trafficking and its interaction with MVB, we tested whether this lysosomal channel is disturbed by visfatin. By GCaMP3 Ca2+ imaging and whole-lysosome patch clamp recording, we found that ML-SA5 (TRPML1 channel agonist) induced remarkable lysosomal Ca2+ release in WT/WT SMCs, which was attenuated by visfatin. In SMCs lacking Asah1 gene, however, ML-SA5 induced much less Ca2+ release from lysosomes, which was almost abolished by visfatin. Lysosome trafficking analysis showed that ML-SA5 activation of lysosomal TRPML1 channels markedly increased lysosome movement in SMCs, which was significantly inhibited by visfatin and Asah1 gene deletion. Based on these results, we concluded that lysosomal AC deficiency leads to dysregulation of actin polymerization and integrin recycling in SMCs, which may be a novel molecular mechanism of SMCSS and ultimate arterial wall stiffening during obesity.

This study was supported by NIH grants HL057244 and HL075316.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Understanding the role of Cysteinyl leukotriene receptor signaling in cancer progression and metastasis
Authors: Sabu Kattuman Emma Elizabeth , Teegala Lakshminarayan Reddy , AV Thanusha , Thodeti Charles , Paruchuri Sailaja
Published: May 2023

Background: Cysteinyl leukotrienes (cys-LTs) are pro-inflammatory mediators which enhance inflammation through cysteinyl leukotriene receptor 1 (CysLT1R) and cysteinyl leukotriene receptor 2 (CysLT2R). Although cys-LTs and their receptors are mainly implicated in asthma and inflammation, recent association of inflammation with cancer has led to enhanced interest in understanding these players in cancer progression and metastasis. However, the exact molecular mechanisms underlying key processes in cancer- proliferation, migration and invasion ( in vitro), tumor progression and metastasis (in vivo) by these mediators remain unexplored. Further, the contribution of these receptors in tumor vs stromal microenvironment, and their interactions is unknown. A thorough investigation of these receptor signaling can reveal their therapeutic potential in cancer progression and metastasis. Objective: To study how cysteinyl leukotriene receptors contribute to melanoma and breast cancer initiation, progression, and metastasis Methods: Expression and functional analysis of CysLTR was determined by transcript (qPCR), western blotting (protein) and by calcium flux assays. Cancer cell survival and proliferation were analyzed by XTT and BrDU assays. Activation of intracellular signaling molecules was determined by western blotting using phospho-specific antibodies. Migration and invasion were analyzed using trans-well assays. Tumors were induced in WT, Cysltr1-/- and Cysltr2-/- mice and their progression and metastasis were evaluated. Results: Breast cancer (EO771) and melanoma (Luc-B16F10-GFP) cells express high levels of CysLT2R compared to CysLT1R. Further, stimulation of tumor cells with cys-LTs caused phosphorylation of Erk, p38, JNK, Akt, and CREB independent of epidermal growth factor receptor (EGFR). Notably, treatment of tumor cells with CysLTR antagonists significantly reduced migratory capability of the cells suggesting the vital role played by CysLTRs in tumor cell migration. Finally, we observed a significant reduction in the tumor volume in mice deficient in CysLTR ( Cysltr1-/- and Cysltr2-/-) mice compared to the WT mice, indicating a role for CysLTR in mediating tumor growth in vivo. Conclusion: Cysteinyl leukotrienes play an important role in promoting tumor proliferation, and metastasis via CysLTR and therefore, understanding their signaling and targeting them can offer potential targets for cancer therapy.

This work was supported by National Institutes of Health (R01AI144115 and R01HL148585)

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Activation of select airway afferent subpopulations evokes cardiopulmonary reflexes
Authors: Darcey Teresa , Taylor-Clark Thomas
Published: May 2023

Activation of airway sensory nerves causes respiratory and autonomic reflexes. The majority of the sensory nerves are only sensitive to noxious stimuli, such as inflammation, infection, irritants and pollutants. Activation of these nociceptive sensory nerves evokes protective mechanisms such as apnea, cough and bradycardia. However, these reflexes may also contribute to disease morbidity when excessively or inappropriately activated. Airway nociceptive sensory nerves, which are largely projected from the vagal ganglia (nodose and jugular ganglion), are heterogeneous with respect to gene expression and neuroanatomy, and our objective is to characterize the reflexes evoked by activation of specific afferent subsets. To selectively activate vagal afferent subpopulations in vivo, mice were exposed to nebulized selective stimuli such as capsaicin (transient receptor potential (TRP) vanilloid 1 (V1) agonist), allyl isothiocyanate (AITC, TRP ankyrin 1 (A1) agonist), adenosine (nodose-selective agonist) and clozapine-N-oxide (CNO, selective agonist for the designer receptors exclusively activated by designer drugs (DREADD) stimulatory receptor hM3Dq). hM3Dq expression was selectively expressed in sensory subpopulations under the control of Cre recombinase in TRPV1-cre (all nociceptors), Tac1-cre (peptidergic/jugular-originating nerves) and P2X2-cre (nodose-originating nerves). ECGs were recorded via radiotelemetry following implantation of biopotential sensing modules, and respiration was measured via whole body plethysmography. Dose response experiments have been performed for capsaicin, AITC and CNO to determine the minimum dose required to evoke the cardiopulmonary reflex, all of which produce significant bradypnea and bradycardia. Capsaicin and AITC produced comparable levels of bradypnea, but AITC evoked a stronger bradycardia than capsaicin. Bradypnea also appeared at lower doses for both capsaicin and AITC compared to the higher doses required to evoke bradycardia. Adenosine administration produced minimal bradypnea and bradycardia compared to CNO administration on the P2X2+ nodose population which produced a larger bradypnea and bradycardia. CNO-driven activation of the Tac1+ jugular population also evoked significant bradypnea and bradycardia. Our data indicate that stimulation of nociceptive afferents (TRPV1+ and/or TRPA1+) selectively evokes bradypnea and bradycardia in freely moving mice. However, our data also suggests that functionally-distinct nociceptive subpopulations may differentially regulate cardiopulmonary reflexes.

NIH R01: HL152219; NIH T32: HL160529

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Loss of Claudin-3 Impairs Intestinal Barrier Function and Gut Microbiota to Promote Colitis
Authors: Singh Amar , Ahmad Rizwan , Thapa Ishwor , Kumar Balawant , Bastola Dhundy , Dhawan Punita
Published: May 2023

Objective: Inflammatory Bowel Disease (IBD) is multifactorial autoimmune disorder where dysregulation of the gut barrier and gut microbiota (Dysbiosis) play critical role in disease onset and progression. A leaky gut often coexists with the dysbiotic gut microbiota, however a pathobiological integration is not well understood. Intestinal claudin-3 expression is robust, and we have reported that its loss promotes gut permeability and colon cancer. Increased gut permeability and colon cancer risk characterize Inflammatory Bowel Disease (IBD). The current study was undertaken to delineate the status and role of claudin-3 expression in IBD. Methods: Multiple murine models of colitis and IBD patient biopsy were used. Claudin-3KO mice were used to determine causal role. Multiplex ELISA, RNAseq and 16S DNA sequencing helped determine inflammatory cytokines, transcriptomic changes, and gut microbiota diversity, respectively. Fecal microbiota transplantation (FMT) and antibiotic treatment studies were done to test the role of claudin-3/gut dysbiosis axis in promoting IBD. Results: A significant decrease in claudin-3 expression was observed in IBD patient samples or the colon of mice subjected to DSS- (2.5% w/v) or C. rodentium-colitis (5 x108 CFU/oral). colitis (p<0.001). To test the causal role, claudin-3KO mice were subjected to DSS-colitis (acute and chronic), and infectious colitis. A significant change in the body weight, colon thickness, and mucosal injury score (p<0.001) characterized the colitis challenged claudin-3KO versus WT mice. P-Stat3 expression was highly upregulated in colitis challenged claudin-3KO mice. Interestingly, administration of an antibiotic cocktail rescued the colitis severity in claudin-3KO mice. The 16s metagenomics further revealed that the gut microbiota of claudin-3KO mice is diverse and clustered distinctly from the WT mice. To determine if gut dysbiosis in claudin-3KO mice promotes susceptibility to colitis, we performed FMT from naïve Claudin-3KO mice to germ-free WT mice. When subjected to DSS-colitis, germ-free mice transplanted with Claudin3-KO gut microbiota showed significantly higher colitis severity versus WT (p<0.05). Conclusion: We summarize that the loss of colonic Cldn3 deregulates mucosal barrier integrity to induce gut dysbiosis and susceptibility to IBD. We propose that claudin-3 can be a novel therapeutic target in strengthening the gut barrier integrity to diminish IBD susceptibility.

National Institute of Health, Veterans Administration

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Insight on the loading-mediated regulation of Runx1 in skeletal muscle
Authors: Koopmans Pieter , Jones Ronald , von Walden Ferdinand , Vechetti Ivan , Murach Kevin
Published: May 2023

Skeletal muscle adaptation during conditions of dynamic muscle loading such as resistance-type exercise occurs in conjunction with pronounced changes in gene expression. The objective of this study was to comprehensively evaluate gene expression at the onset of rapid muscle hypertrophy in mice. We analyzed the global, nascent, stable, and myonuclear transcriptome utilizing RNA-sequencing. C57BL6/J mice were treated with 5-ethenyl uridine at the end of 72 hours of synergist ablation mechanical overload of the plantaris muscle to assess transcriptional dynamics; sham mice served as controls. Mice with in vivo fluorescent myonuclear labeling were used to obtain RNA-sequencing in exclusively myonuclei from overloaded and sham mice. In these analyses, RUNX family transcription factor 1 ( Runx1, or Aml1) was significantly elevated in all conditions (adj. p<0.05x10-15) and was among the most induced genes across datasets. These findings allude to Runx1 as a highly regulated mediator of muscle hypertrophy that is enriched specifically in muscle fibers during loading. Myonucleus-specific global DNA methylome analysis also report exon and intron CpG hypomethylation in the Runx1 gene after overload. As gene body methylation can mediate alternative splicing, we subsequently hypothesized Runx1 may be subject to alternative splicing and conducted preliminary analyses of RNA splice isoforms present after acute overload. We found that a non-canonical isoform of Runx1 ( Runx1-202, coding for a 387 amino acid protein) was relatively more induced than the Runx1-201 transcript that codes for the full-length 465 amino acid protein (30- versus 17-fold induction, respectively), while Runx1 is essentially not expressed in sham muscle. Ongoing analysis will validate Runx1 splice variant expression during overload in muscle, the potential influence of DNA methylation, and the impact of the Runx1 short isoform on muscle hypertrophy.

This work is supported by the National Institutes of Health under grant R00 AG063994 to Kevin A. Murach.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Sex differences in swallowing response to Gaussian stochastic surface electrical stimulation
Authors: Morimoto In , Frazure Michael , Iceman Kimberly , Koike Takuji , Pitts Teresa
Published: May 2023

One of the rehabilitation methods in practical use for dysphagia is electrical stimulation therapy, usually by stimulating the anterior neck muscles via surface electrodes. Electrostimulation therapy does not directly induce swallowing, but is used as resistance training or to alter drive to swallow muscles. Techniques to stimulate the sensory nervous system have been investigated as possible rehabilitation methods to activate the entire swallowing reflex circuit (such as direct magnetic stimulation of the primary somatosensory cortex). We hypothesized that electrical stimulation of the posterior thoracic region using surface electrodes on the back could work in a similar way to magnetic stimulation therapy to improve swallowing movements. We placed stimulating electrodes at three different locations on the back, neck, and subclavian region of adult Sprague Dawley rats ( n = 18). Using a stochastic paradigm, Gaussian probability electrical stimulation was applied to each site at a median frequency of 300 Hz. Natural swallow was evoked by oral water infusion, and swallow activity was recorded with electromyogram (EMG) wires placed in three swallow-related muscles: mylohyoid (laryngeal elevator), thyroarytenoid (laryngeal adductor), and thyropharyngeus (pharyngeal constrictor). A total of four 120 second electrical stimulus trials were applied with a median frequency of 300 Hz in a Gaussian distribution. EMG amplitudes during swallows after each stimulus were compared to those generated during control swallows. Results showed stimulator placement on the back facilitated all three muscles (mylohyoid, thyroarytenoid, and thyropharyngeus) in all male rats, and in some female rats. Stimulation placed on the lateral neck affected only the thyropharyngeus in male rats, and only the thyroarytenoid in female rats. EMG amplitudes were unchanged following subclavian stimulation. In conclusion, our finding that Gaussian electrical stimulation of the back activated a complement of swallowing muscles in male rats suggests that this may represent a novel swallowing treatment method. Additionally, male and female rats responded differently to simulation, indicating that potential sex differences need to be further elucidated.

This work was supported by NIH grants HL 111215, HL 103415 and OT20D001983, the Craig H. Neilsen Foundation Pilot Research Grant 546714, Kentucky Spinal Cord and Head Injury Research Trust, and the Commonwealth of Kentucky Challenge for Excellence.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Chronic exercise in pigs shifts post-transcriptional control of the myocardial inflammasome
Authors: Samani Stephanie , Barlow Shayne , Freeburg Lisa , Jones Traci , Sarzynski Mark , Zile Michael , Shazly Tarek , Spinale Francis
Published: May 2023

Background: Chronic exercise protocols have demonstrated a beneficial effect on overall cardiovascular health, however, the direct effects on left ventricular (LV) function and the relation to changes in post-transcriptional regulatory checkpoints, that is the microRNAs (miRs), and what downstream processes may be affected, remains unexplored. Accordingly, this study developed a chronic exercise protocol in mature pigs and examined LV function and myocardial mRNA profiles. Methods and Results: Pigs (n=9; 25 Kg) underwent a treadmill protocol (4 weeks, 10° elevation, 2.5 mph, 10 minutes) in which LV ejection fraction (LV EF) and end-diastolic volume (LV EDV) were measured by echocardiography. Age matched, non-exercise pigs (n=6) served as referent controls. LV myocardial samples were subjected to an 84 miR array using rt-PCR. All results are reported as mean ± SEM. LV EDV (54.8 ± 3.1 vs 67.4 ± 3.3 mL, p≤0.05) and LV EF (66.4 ± 1.8 vs 82.0 ± 0.7 %, p≤0.05) increased with exercise indicative of a successful training effect. A total of 25 miRs were significantly upregulated (56%) or downregulated (44%) following exercise. Using miR mapping algorithms, miR-22 and miR-30e, which fell by over 3-fold change with exercise (rt-PCR, -3.07 ± 0.92 and -3.28 ± 1.08 respectively, p≤0.05), mapped to the NLRP3 inflammasome. NLRP-3 mRNA (rt-PCR) levels fell by over 2-fold with exercise (-2.65 ± 0.62, p≤0.05). Conclusion: A chronic exercise protocol in pigs induced a unique miR profile that was associated with changes in LV geometry and function. In particular, several miRs mapped to regulatory elements of the local inflammatory pathway- the inflammasome. These unique findings demonstrated a clear shift in post-transcriptional pathways occur with chronic exercise and reduces LV myocardial inflammasome profiles.

This work was supported in part by National Institutes of Health grant R01HL130972-01A1 (F.G.S.) & R01HL5949 (F.G.S.) as well as a Merit Award from the Veterans Health Administration, BX000168-10A1 (F.G.S.) & BX005320 (F.G.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Prospective assessment of nighttime respiratory disturbance in multiple myeloma patients
Authors: Jedlicka Charles , Haasl Calista , Witherell Carly , Tomasson Michael , Bates Melissa
Published: May 2023

Chronic intermittent hypoxia, a feature of sleep apnea, is a potent driver of solid tumor cancers and promotes lethal engraftment of malignant plasma cells in a mouse model. The objective of this study was to investigate if nighttime respiratory disturbances affect clinical outcomes in a multiple myeloma patient population. To do so, we prospectively assessed nighttime respiratory disturbance index (RDI) in 44 patients (27 male, 17 female) diagnosed with multiple myeloma at the University of Iowa Hospitals and Clinics. Following this assessment, we categorized patients by RDI and utilized electronic medical records to explore differences in routine myeloma clinical measures. We found 93% of the patients had an RDI equal to clinical sleep apnea. 39% of patients had a moderate or severe RDI. In comparing these patients to those with low RDI, there were no statistical differences in any clinical performance indicator. Additionally, there were no differences in disease symptoms, multiple myeloma staging, or antibody type between these groups. However, patients with a higher nighttime RDI were less likely to respond to induction chemotherapy (p=0.046), a predictor of poor disease prognosis. These data support the hypothesis that nighttime respiratory disturbances negatively impact multiple myeloma patients, but this impact may not be evident in routine clinical tests of patient performance.

This research is supported by NIH award R01CA244271

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Age and sympathetic transduction to blood pressure
Authors: Bigalke Jeremy , Cleveland Emily , Young Benjamin , Fadel Paul , Carter Jason
Published: May 2023

Aging has been associated with reduced sympathetic transduction using multiple methodologies, including signal-averaging, in which the change in mean arterial pressure (MAP) following a muscle sympathetic nerve (MSNA) burst is tracked for 10-15 cardiac cycles. Recent reports suggest that this methodology is impacted by the location of an MSNA burst relative to the average resting blood pressure. The current study examined age differences in MSNA burst dispersion around the average MAP and its potential impact on sympathetic transduction. We hypothesized that aging would be associated with more MSNA bursts occurring at MAP values above mean resting MAP, contributing in part to reductions in sympathetic transduction. Beat-to-beat blood pressure and MSNA were recorded during 5-minute supine rest in 27 young (YA; 13F, age: 25±1 yrs, BMI: 25±1 kg/m2) and 26 older (OA; 15F, age: 59±1 yrs, BMI: 26±1 kg/m2) adults. Resting beat-to-beat MAP values were split into low (T1), middle (T2), and high (T3) tertiles, and transduction of bursts occurring within each tertile was calculated using signal-averaging. OA exhibited higher resting MSNA burst frequency (YA: 24±2 vs. OA: 33±2 bursts/min, P<.001). OA exhibited blunted overall sympathetic transduction (YA: Δ1.5±0.1 vs. OA: Δ0.9±0.1 mmHg, P=.005). When separated by MAP tertiles, age differences in transduction were only observed in T3 (YA: Δ-0.4±0.1 vs. OA: Δ-1.0±0.1 mmHg, P=.005) but not T1 (YA: Δ2.3±0.1 vs. OA: Δ2.2±0.2 mmHg, P=.456) or T2 (YA: Δ0.7±0.1 vs. OA: Δ0.4±0.1 mmHg, P=.337). Since age differences were only observed at T3, we next examined only bursts occurring above the average MAP. A greater proportion of bursts occurred above the average MAP in OA (YA: 30±2 vs. OA: 40±1 %, P<.001), and a larger proportion of these bursts were associated with a depressor response in OA (65±2%) compared to YA (56±2%, P=.005). Nevertheless, assessment of bursts occurring above the average MAP that were associated with a pressor response revealed a blunted transduction in OA (YA: Δ2.7±0.3 vs. OA: Δ1.7±0.2 mmHg, P=.016). These results indicate an age-related increase in MSNA burst occurrence above the average resting MAP, with a greater majority of these bursts being associated with depressor responses in OA. Further, age-associated reductions in transduction are observed following MSNA bursts associated with a pressor response occurring above the average resting MAP.

Support: NIH (AA-024892, U54GM115371; P20GM103474, 2TL1 TR002318)

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Manipulating thyroid hormone levels alters development of skeletal muscle mitochondria in nestling red-winged blackbirds
Authors: Dzialowski Edward , Sirsat Tushar , Sirsat Sarah , Pineda Megan , Price Edwin , Crossley Janna
Published: May 2023

Thyroid hormones are key regulators of development and metabolism in vertebrates. Red-winged blackbirds are an altricial species that exhibit an increase in plasma 3,3’, 5-triiodo-L-thyronine (T3) levels during the first 5 days post-hatch (dph), begin to develop endothermic metabolic responses by 7 dph, and fledge within 10 days of hatching. To better understand the role thyroid hormones play in the endothermic metabolic development in an altricial species, we treated nestling red-winged blackbirds on 2, 3, and 5 dph with either methimazole to induce hypothyroidism or supplemental T3 to induce hyperthyroidism. We examined mitochondria function in breast and thigh skeletal muscle at 5, 7 and 9 dph in permeabilized muscle fibers. Hypothyroid conditions prior to day 5 post-hatching induced lower oxygen flux during oxidative phosphorylation through complexes I and II than controls in both breast and thigh skeletal muscles of 7 and 9 dph nestlings. Elevating thyroid hormones during the first 5 dph resulted in greater leak respiration but no change in oxidative phosphorylation respiration later in the nestling period. These data suggest that thyroid hormone levels play a role in development of skeletal muscle mitochondrial function and may be a foundational mechanism by which endothermic capacity is achieved by neonate altricial birds.

NSF 1146758

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Effects of chronic neonatal hyperoxia-induced bronchopulmonary dysplasia on breathing, energy expenditure, and growth in young, adolescent, and adult mice
Authors: Mouradian Gary , Dir Brooke , Grobe Connie , Reho John , Grobe Justin , Segar Jeffrey
Published: May 2023

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease associated with preterm birth. Growth failure is common in infants with BPD and is associated with increased resting metabolic rate (RMR). Whether increased RMR and growth failure are a consequence of BPD lung pathology per se, or a consequence of clinical interventions remains unknown. Herein, we sought to determine the effects of BPD-like lung injury on breathing, growth, and energy expenditure in C57BL/6J male mice exposed to chronic hyperoxia (Hx; 70% O2; n=5) or normoxia (Nx; n=6) in the neonatal period (postnatal day (P) 0-14). Consistent with prior reports and human BPD, Hx lungs at P21 had reduced alveoli and alveolar density indicated via H&E lung sections. Also, Hx mice had altered respiratory responses to acute hypoxia (10 min; 12% O2) including a reduced hypoxic ventilatory response (108±6 Nx vs 89±4 % Hx; p<0.05) and drive to breathe (tidal volume/inspiratory time; 0.98±0.06 vs 0.76±0.04; p<0.05). The pattern of breathing during the acute challenge favors longer inspiratory time (132±6 vs 170±9 ms, p<0.05) which may reflect a compensatory response to reduced alveoli. Despite these differences, no differences in body composition (body, fat and fat-free masses, and total body water) were observed at P21, 6wks, or 8wks of life. Furthermore, there were no differences in ingestive behaviors, or total or resting aerobic heat production (kcal/h) at 8 wks of age, yet Hx mice had reduced locomotor activity (199±10 vs 154±11 m/d; p<0.05) which may indicate reduced exercise capacity. In a subset of mice (n=2/group), a 20% increase in right ventricular mass was noted, consistent with some degree of pulmonary hypertension, along with a 3% decrease in hematocrit, which may reflect a programmed change in hematopoiesis after early-life Hx. Together, these data document the impact of BPD-like lung injury on key physiological parameters and support the iconoclastic concept that BPD pathology per se does not drive increased RMR or growth failure. By extension, other factors – possibly including side-effects of well-intentioned clinical interventions – may underly growth failure in children with BPD. We speculate that sodium depletion resulting from diuretic therapy, which is common for this condition and known to impact infant growth, may be an important contributor to growth failure in infants with BPD.

GCM: AHA 20CDA35310121; JLG: DK133121, HL134850, and HL084207; JLS: DK133121

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Embedding design thinking, career planning and teamwork into the curriculum better prepares life science students for research and alternate science careers
Authors: French Michelle , Miliotis Helen , Andreopoulos Stavroula , Laposa Rebecca , Arnot Michelle
Published: May 2023

Many undergraduates have either a narrow or vague idea of their career path which causes stress and can result in them leaving science. In addition, they often lack confidence or the knowledge needed to pursue independent research project courses in their senior year. To broaden student career perspectives, promote adaptability and build research skills, we developed a third-year course: Research Readiness and Advancing Biomedical Discoveries. This flipped course features online pre-class modules and extensive in-class group work. Online module topics include: writing a research proposal, project management and attributes of a successful scientist ( https://experientialmodules.utoronto.ca/research-readiness/ ). We also incorporated design-your-life ( http://lifedesignlab.stanford.edu/ ) team activities (DYL) such as brainstorming, articulating alternate life plans (Odyssey planning), and networking to help students develop novel scientific research proposals and to support their own creative career planning. To assess student perceptions of course components, we conducted anonymous student surveys three times in each offering of the course using both 5-point Likert scales and open-ended prompts for student feedback (Univ. Toronto REB#18345). Responses to open-ended survey questions were independently analyzed for broad themes by two third-party research assistants. Over the three years of course offerings, 86% of students reported feeling better prepared for research and other opportunities after graduation, 87% of students reported being encouraged to consider flexible career paths, and 87% reported they have realized the importance of teamwork (n=121). Written comments included: “ The research proposal was an incredible assignment because it gave me insight into what I would be doing in research and let me think of my own idea.” and “ [Odyssey planning] helps me to rethink my choices. Why can’t I make different choices? What is holding me back?. I think I need more diverse experience in area of biomedical science to answer these questions. ” Thus, students perceive that our novel course better prepares students for research and alternate science careers.

Learning and Education Advancement Fund (LEAF) Impact grant, University of Toronto, Career Readiness Fund, Faculty of Arts and Science, University of Toronto, Online Undergraduate Course Initiative Fund, University of Toronto

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Beneficial cardiovascular-renal effects of exercise on aging male and female obese TallyHo/Jng mice
Authors: Wadhwa Vishwas , Gadicherla Arushi , de Souza Aline , Korolowicz Kyle , Ecelbarger Carolyn
Published: May 2023

The benefits of aerobic exercise on cardiorenal health in aging, insulin-resistant individuals are not fully understood. We hypothesized that chronic treadmill exercise (aerobic training) of overweight aging (10-month old) insulin-resistant TallyHo/Jng (TH) mice (prone to type 2 diabetes) would improve the comprehensive cardiovascular phenotype and metabolism. Male (M) and female (F) TH mice (n = 10/group) underwent treadmill running exercise (Ex, 10-19 meters/min) for 15-30 minutes, 4X/week or remained sedentary (Sd) for 9 weeks. Final body weights were 20 and 30% lower in M and F Ex, relative to same sex Sd groups, respectively. Ultrasound conducted a week prior to euthanizing showed renal blood flow (external velocity, pulse wave doppler) was significantly increased by Ex on average 26 and 24% in M and F, respectively (2-way ANOVA for Ex, p = 0.0089). With regard to cardiac features, while cardiac output was not significantly different between groups, stroke volume was increased in both sexes by Ex (9% in M, 5% in F). Whereas, cardiac ejection fraction and fractional shortening were significantly increased by Ex in female, but not male mice (p < 0.03 between FEx and FSd groups by Šidák's multiple comparisons testing). Left ventricular mass was not altered by Ex, but about 20% higher in M than F mice. Dual X-Ray Absorptiometry (DEXA) scanning revealed increased bone mineral content and density, in both sexes due to Ex, as well as, reduced body fat, but only in the F mice (p < 0.0001). Body fat was (%): 26.1 ± 0.4 (MSd); 26.1 ± 0.6 (MEx); 31.7 ± 1.8 (FSd); 20.8 ± 1.1 (FEx). Total lean mass was significantly higher in M, but not affected by Ex. Ex reduced final blood glucose (4-hour fasted, p = 0.0007 for Ex, mg/dl): 142 ± 5 (MSd); 128 ± 5 (MEx); 137 ± 4 (FSd); 117 ± 4 (FEx). Most fat pads (weighed at euthanasia) were reduced in mass in the F by Ex, but not necessarily in the M. Brown fat was increased by exercise in M, but reduced in F (g/40 g·bw): 0.34 ± 0.02 (MSd); 0.44 ± 0.03 (MEx); 0.37 ± 0.03 (FSd); 0.25 ± 0.04 (FEx), p = 0.0007 for interaction of exercise with sex (2-way ANOVA). Kidney, liver, and heart final wet weights were not affected by Ex, but lower in F (p < 0.0001 for sex for all 3). In conclusion, treadmill exercise to obese, aging TH M and F mice resulted in a several improved cardio-renal indices in addition to reducing weight, visceral fat mass, and increasing bone density. These studies support the prescription of vigorous cardiovascular exercise in aging, obese, insulin-resistant individuals.

Funding to CE provided by the Marriott Foundation, the NIH CTSA Award pre-pilot, and internal Georgetown University sources

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Effects of the thromboxane receptor antagonist S18886 in the porcine coronary circulation
Authors: Tucker Selina , Warne Cooper , Essajee Salman , Goulopoulou Styliani , Dick Gregory , Tune Johnathan
Published: May 2023

Thromboxane A2 (TxA2) is a potent coronary vasoconstrictor that has been implicated in promoting decreases in myocardial perfusion in a variety of (patho)-physiologic conditions. S18886 is a promising orally-active TxA2 receptor antagonist currently approved for investigational clinical use. However, the coronary vascular effects of S18886 are unknown and its specificity and affinity for the thromboxane receptor in the coronary circulation remain unclear. We tested the hypothesis that administration of S18886 dose-dependently attenuates coronary vasoconstriction to the TxA2 mimetic U46619 without influencing coronary responses to prostaglandin F2α, acetylcholine, or smooth muscle depolarization (K+). Experiments to test this hypothesis were performed in male (n = 5) and female (n = 6) domestic swine. Hearts were excised and the left circumflex coronary artery isolated, cleaned of periadventitial fat, and cut into 3 mm rings. Isometric tension of coronary artery rings was measured in response to log order increments of U46619 (1 nM to 1 μM) with and without S18886 (0.1-100 nM). Similar isometric studies were conducted with prostaglandin F2α (10 nM-10 μM), acetylcholine (0.1-10 μM), and KCl (5-90 mM). U46619 induced concentration dependent increases in tension development of isolated coronary artery rings (average EC50 of 42 ± 19 nM). Incubation of coronary arteries with S18886 (1 nM) significantly attenuated coronary vasoconstriction to U46619 resulting in a rightward shift of the EC50 to 187 ± 38 nM (P < 0.02). Vehicle had no effect on U46619-induced contractions. Higher concentrations of S18886 (10nM and 100nM) dose-dependently reduced U46619-induced contractions by 77% ± 3 and 93% ± 6 respectively. S18886 (1 nM) antagonized coronary vasoconstriction of prostaglandin F2α (10 μM) by 68% ± 5 (P < 0.0001) but had no effect on either acetylcholine or KCl-induced contraction. Data from this investigation indicate that S18886 is an effective antagonist of U46619-induced vasoconstriction in the porcine coronary circulation. While S18886 does not influence coronary smooth muscle response to either acetylcholine or activation of L-type Ca2+ channels, attenuation of prostaglandin F2α suggests the antagonists specificity may extend beyond TxA2 receptor signaling.

NIH R01HL158723

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Exertional heart stroke causes long-term obesity and cardiac hypertrophy in mice
Authors: Alzahrani Jamal , Gambino Bryce , Delgado Cristina , Rua Michael , Young Iris , Cusack Kevin , Clanton Thomas
Published: May 2023

Exertional heat stroke (EHS) is a life-threatening illness that can lead to short- and long-term adverse health outcomes. Several human epidemiology studies have shown that heat stroke exposure is highly associated with the development of cardiovascular disease later in life. However, whether EHS causes heart disease or individuals with predispositions to heart disease are more susceptible to EHS is unknown. Previously, our laboratory demonstrated metabolic abnormalities in the myocardium of mice, two weeks after EHS, characterized by lipid accumulation. In this study, we hypothesized that EHS exposure in mice leads to long-term susceptibilities to cardiovascular disease that is accelerated by co-exposure to a Western diet. METHODS: Sixty-four male (n=32) and female (n=32) C57BL/6 mice were exposed to either EHS (forced wheel running in 34.5°C for males and 37.5°C for females) or sham exercise controls (EXC, forced wheel running in ~22.5°C). Fourteen days later, mice were placed on either a Western diet (WD) or a standard diet (SD) and then followed for 9 additional weeks. At week 12, post interventions (EHS or EXC), animals were euthanized and samples collected for analysis. RESULTS: Male mice exposed to EHS with either WD ( P = 0.0001) or SD ( P = 0.0001) gained more body mass over the 9-week diet period compared to diet matched EXC controls. Also, regardless of diet, male mice exposed to EHS consumed more food compared to matched EXC (WD: P < 0.005 and SD: P < 0.04). However, only female mice exposed to EHS with WD gained more body mass compared to female EXC mice with WD ( P < 0.04). At the end of the study, and regardless of diet, male mice exposed to EHS showed enlarged hearts in terms of absolute mass (WD: P=0.0241, SD: P=0.0069) and relative mass/tibia length (WD: P=0.013, SD P=0.03). On the other hand, EHS female mice exposed to WD showed enlarged heart mass compared to EHS on SD ( P=0.0005). CONCLUSIONS: These results demonstrate that EHS exposure in mice leads to a long-term metabolic disorder characterized by greatly accelerated weight gain, greater appetite and cardiac hypertrophy. Effects were more evident and consistent in males. Such a response is typical of early stages of metabolic syndrome and would likely contribute to eventual cardiac disease. Therefore, the data is consistent with EHS exposure being a risk factor for long term heart disease.

U.S. Army Grant BA180078 and from King Saud University, Saudi Arabia

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Rare Single-Nucleotide Variants that Impact Human ENaC Function
Authors: Chen Mindy , Chen Jingxin , Wang Xueqi , Sheng Shaohu , Kleyman Thomas
Published: May 2023

While single-nucleotide variants (SNV) in ENaC coding region occur throughout functional domains, only a few SNVs exhibit pathophysiological phenotypes with mendelian inheritance. Since a SNV that alters ENaC’s ability to sense extracellular Na⁺ has been linked to hypertension, we hypothesize that other ENaC SNVs that alter channel activity will also affect blood pressure. To identify novel low-frequency ENaC SNVs that change ENaC activity, we heterologously expressed human ENaC gamma subunit variants together with wildtype alpha and beta subunits in Xenopus oocytes. We performed two-electrode-voltage clamp (TEVC) to record amiloride-sensitive currents of these channels. We characterized rare human SNVs found in multiple genomic databases covering various γENaC domains. Among the selected SNVs, we identified three gain-of-function variants (γV110I, γG149A, γV619L) with significantly greater amiloride sensitive currents (P<0.001, n=25~55) than wildtype channels. In addition, two loss-of-function variants (γG58R, γH280R) displayed significantly decreased currents (P<0.001, n=20~25) than wildtype channels. Future studies investigate the functional effects of these SNVs by assessing the gating behavior and surface expression of these channels. These data suggests that: Although low in prevalence but high in coverage throughout the ENaC coding region, rare SNVs directly modify the channel function. Our results add the growing list of human ENaC variants that alter channel activity and could impact blood pressure in humans.

National Institutes of Health Grants R01 HL147818 and P30 DK079307

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.