bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deoxycorticosterone-acetate salt-sensitive hypertension initiates with intracellular K+ and water loss
Authors: Minegishi Shintaro , Morisawa Norihiko , Wild Johannes , Takase-Minegishi Kaoru , Marton Adriana , Lim Tzy Tiing , Walsh Stephen 
Published: May 2024

Background: Textbook teaching pretends that Na+-driven extracellular fluid and blood volume expansion may cause hypertension. We tested the alternative hypothesis, namely that K+ loss-driven intracellular volume contraction causes hypertension. Methods: We tested the effect of deoxycorticosterone acetate (DOCA; 25 mg pellet) in mice on low Na+ diet (0.02-0.03%) without (tap water), or with Na+ in their drinking water (1% NaCl or 1.44% NaHCO3). We measured BP with radio-telemetry, and analysed body Na+, K+, and water content 2, 6, and 12 days after initiation of DOCA treatment. We monitored food intake, solute and water excretion in urine and stool, and quantified renal and cutaneous blood flow by pulse-wave/laser Doppler spectroscopy. Results: DOCA NaCl treatment initially reduced intracellular K+ and water content, and elevated BP without accompanying Na+ retention. To re-hydrate the intracellular volume space, hypertensive DOCA NaCl−treated mice secondarily replaced lost intracellular K+ by Na+ solutes, increased fluid intake, reduced renal solute-free water clearance, constricted renal blood vessels, and reduced dermal blood flow. Normotensive DOCA NaHCO3-treated mice similarly lost intracellular K+, but immediately compensated by intracellular Na+ accumulation, and therefore experienced no intracellular volume contraction. Without prolonged under-hydration of their K+-space, DOCA NaHCO3-treated mice neither showed augmentation of renal or dermal water conservation, nor vasoconstriction and blood flow reduction, and their BP remained normal despite body Na+ excess. Conclusions: DOCA salt-sensitive hypertension is caused by K+-driven under-hydration, and not by Na+-driven over-hydration. The BP increase is explainable by secondary-adaptive multi-organ water conservation physiology, but not by Na+-driven water excretion physiology. National Medical Research Council (NMRC) of Singapore to the Duke-NUS Medical School, the German Federal Ministry for Economics and Technology/DLR Forschung unter Weltraumbedingungen (Mars500-III; 50WB2024). This is the full abstract presented at the American Physiology Summit 2024 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.
Deleting the Ribosomal Prolyl Hydroxylase OGFOD1 Leads to Protection in Pressure Overload-Induced Cardiac Hypertrophy in Mice
Authors: Kennedy Leslie M. , Gao Erhe 
Published: May 2024

Molecular changes occurring in heart failure have largely focused on the transcriptional landscape. However, disparities between transcript and protein abundances emphasize the need to understand proteomic changes occurring in heart failure as well the mechanisms governing these changes. Post-translational modifications (PTMs) are a well-known mechanism for regulating protein turnover and activity. A lesser-known enzyme that catalyzes the addition of PTMs on the translational machinery is 2-oxoglutarate- and Fe2+-dependent oxygenase domain-containing protein 1 (OGFOD1). Our published evidence shows OGFOD1 RNA and protein accumulate in human failing hearts, indicating a potential role for this enzyme in heart disease. Because heart failure can develop from many pathologies, including hypertrophy, we investigated the role of OGFOD1 in cardiac hypertrophy. We induced hypertrophy via pharmacological β-adrenergic stimulation by treating wildtype (WT) and OGFOD1-knockout (KO) mice with isoproterenol (ISO), where we found that KO mice were protected from ISO-induced hypertrophy. Based on our findings that OGFOD1-KO mice are protected in ISO-induced cardiac hypertrophy, we tested the hypothesis that KO mice were protected in pressure overload-induced cardiac hypertrophy mediated via transverse aortic constriction (TAC). WT and KO mice were subjected to sham or TAC surgery, and heart weight-to-tibia length (HW/TL) and heart weight-to-body weight (HW/BW) ratios were used to determine extent of hypertrophy. Additionally, hearts were subjected to histological analysis and stained with Masson’s trichrome to assess fibrosis. KO mouse hearts showed significantly less hypertrophy than WT hearts after 2 weeks of TAC according to both HW/TL and HW/BW ratios. KO mice were also protected against cardiac fibrosis. To identify translational changes mediating this protection, future studies will focus on utilizing ribosome profiling to identify actively-translated transcripts whose synthesis is regulated by OGFOD1-mediated prolyl hydroxylation. Results from these studies will provide important mechanistic insight into the therapeutic potential of OGFOD1 in human disease. NHLBI-NIH Intramural Research Program (ZO1-HL002066). This is the full abstract presented at the American Physiology Summit 2024 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.
Signaling switches maintain intercellular communication in the vascular endothelium
Authors: Buckley Charlotte , Lee Matthew , Zhang Xun , Wilson Calum , McCarron John 
Published: May 2024

The endothelium is a sophisticated coordination center that controls a wide range of vascular functions, which include the regulation of blood pressure and blood flow via changes in vascular contractility. To coordinate vascular function, cell communication and interactions are required for tissue level responses to emerge. A significant form of cell-cell communication occurs by the propagation of Ca2+ signals between cells (‘Ca2+ waves’). The objective of our study was to tease apart the mechanisms driving these intercellular Ca2+ waves in the vascular endothelium. We hypothesised that diffusion of free Ca2+ would drive endothelial Ca2+ wave propagation and effect vessel diameter changes. To investigate the mechanisms, intact mesenteric arteries from male Sprague Dawley rats were mounted in an en face preparation, stained with the Ca2+ indicator Cal-520/AM and were imaged on specialised epifluorescence microscopes. Intercellular endothelial signaling was manipulated using caged compounds in concert with precise spatial and temporal control of UV illumination, as well as global or localized drug application. We show that multiple mechanisms maintain communication so that Ca2+ wave propagation occurs irrespective of the status of cell connectivity. Contrary to our hypothesis, regenerative IP3-induced IP3 production transmits Ca2+ signals between adjoining cells and explains the propagated vasodilation that underlies the increased blood flow accompanying tissue activity. By controlling the production of IP3, the inositide is itself suffcient to evoke a regenerative phospholipase C-dependent Ca2+ wave across coupled cells. None of gap junctions, Ca2+ diffusion nor the release of extracellular messengers are required to support this type of intercellular Ca2+ signaling. Surprisingly, when a discontinuity between cells was created using a fire-polished pipette tip, signal was propagated to the other side of the discontinuity and was able to drive propagated vasodilation. Experiments using counter flow and localised perfusion in the absence and presence of P2Y inhibitors revealed that it is ATP released as a diffusible extracellular messenger that transmits Ca2+ signals across endothelial discontinuities. These results show that signaling switches underlie endothelial cell-cell signal transmission, and reveal how communication is maintained in the face of endothelial damage. The findings provide a new framework for understanding Ca2+ wave propagation and cell-cell signaling in the endothelium. This work was funded by the British Heart Foundation (RG/F/20/110007; PG/20/9/34859 ). This is the full abstract presented at the American Physiology Summit 2024 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.
UCHL1 Negatively Regulates Key Factors and Signals Involved in Skeletal Muscle Myogenesis
Authors: Antony Ryan , Aby Katherine , Montgomery Morgan , Li Yifan 
Published: May 2024

Ubiquitin C-terminal hydrolase L1 (UCHL1), a deubiquitinating enzyme that was originally discovered in neurons, is also expressed in skeletal muscle, but its functions remain to be fully understood. Skeletal muscle injury is prevalent in trauma and surgical procedures, and skeletal muscle ischemia-reperfusion (IR) injury is a common and significant public health problem. Myogenesis is a critical process involved in embryonic development, growth, and regeneration following skeletal muscle injury. In this study we report that UCHL1 negatively affects some key factors that are involved in myogenesis and mitophagy, both during muscle development as well as during the regeneration process following IR injury; we hypothesize that UCHL1 is a negative regulator of myogenesis. First, we observed that UCHL1 knockdown in C2C12 myoblasts resulted in increased differentiation and myotube formation. Furthermore, western blot showed that UCHL1 KD consistently upregulated myogenin and MyoD protein levels, key proteins involved in myogenesis, at multiple time points throughout differentiation of the myotubes. Consistent with this in vitro result, skeletal muscle specific knockout (smKO) of UCHL1 increased muscle fiber size in both 1- and 2-month-old mice (p=1.77x10−17, p=6.51x10−13). Additionally, 1- and 2- month-old UCHL1 smKO mice also exhibited increased protein levels of various myosin heavy chain isoforms. To induce IR injury, a tourniquet was placed on the hindlimb for 90 minutes and then removed, allowing for reperfusion for 3-12 days with the contralateral hindlimb serving as a control. Following skeletal muscle IR injury, myogenin and MyoD protein expression was upregulated in injured muscle from UCHL1 smKO mice. Functionally, UCHL1 smKO mice had increased muscle performance after injury compared to control mice when subjected to in situ contractile testing. Interestingly, several mitophagy markers including Parkin and DRP1 were upregulated in IR injured muscle from UCHL1 smKO mice compared to WT mice (p=0.0003, p=0.029). This data suggests that skeletal muscle UCHL1 may function as a negative regulator of myogenesis, both during growth, and repair following injury, possibly by decreasing mitochondrial activity. This work was funded by NIH grant R01HL147105. This is the full abstract presented at the American Physiology Summit 2024 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.
Impact of Aging and Disuse on Markers of Endoplasmic Reticulum Stress and the Unfolded Protein Response
Authors: Michel John Max , Godwin Joshua , Kerr Nathan , Childs Thomas , Booth Frank , Roberts Michael 
Published: May 2024

Aging and disuse can impair skeletal muscle responses to stimuli and are key drivers in dysregulated proteostasis. Such dysfunction can lead to an accumulation of misfolded proteins resulting in endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR). While the UPR blunts global translation and enhances the production of chaperones and foldases, little is known about ERS responses across the lifespan and in disuse contexts. Therefore, the purposes of this study were to examine if: i) the expression of ERS and UPR effector proteins differ across the lifespan in rats, and ii) age-associated patterns were recapitulated by 10 days of hindlimb casting in a separate cohort of rats. We hypothesized that aging would enhance the expression of ERS related proteins, and this expression pattern would be mimicked by 10 days of limb disuse. Male Fischer 344 rats were sacrificed at 3, 6, 12, 18, and 24 months (mo) of age, and plantaris (PLT) and soleus (SOL) muscles were collected for analysis. Six mo female Wistar rats were sacrificed after either 10 days of hindlimb casting or continued ambulation (age matched control), after which whole gastrocnemius muscles were collected for analysis. The effector eukaryotic initiation factor 2 alpha (eIF2a) was different across the lifespan (phospho/pan) in PLT and SOL muscles (p<0.001) and was upregulated in the PLT at 24 mo as compared to 3 mo (P=0.006). The downstream UPR effector C/EBP homologous protein (CHOP) was differentially expressed across the lifespan in PLT and SOL (p<0.001). CHOP was upregulated ~2.79 and 3.08-fold at 18 and 24 mo respectively in the SOL (p<0.001), and 2.62 and 2.44-fold at 18 and 24 mo respectively in the PLT. Finally, principal effector Activating Transcription Factor 6 (ATF6) was differentially expressed across the lifespan (cleaved/pan) in the PLT and SOL (P≤0.024) whereby a 1.23-fold up-regulation was evident at 18 mo in the SOL (P=0.035) and 1.34-fold at 18 mo in the PLT (P=0.026). The CHOP and ATF6 proteins were similarly dysregulated in our disuse model, whereby 1.83-fold (p<0.001) and 1.30-fold (P=0.002) greater values were observed in hind limb casted versus control rats. Effectors of the UPR pathway are upregulated in skeletal muscle across the lifespan in rats, and this effect is recapitulated with disuse. These findings warrant further research for potential therapeutics related to age- and disuse-related skeletal muscle atrophy. Funding for this study was provided by discretionary laboratory funds from MDR. This is the full abstract presented at the American Physiology Summit 2024 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.
Endomorphin-2 and oxycodone paradoxically potentiate the exercise pressor reflex via acid-sensing ion channel 3 (ASIC3) in decerebrated rat
Authors: Anselmi Laura , Kim Joyce , Ducrocq Guillaume , Herold Paul , Ruiz-Velasco Victor , Kaufman Marc 
Published: May 2024

The exercise pressor reflex is evoked by the stimulation of group III and IV muscle afferents in response to muscle contractions. When the contracting muscles are freely perfused, acid-sensing ion channel 3 (ASIC3) on the endings of group IV afferents appear to play a minor role in evoking the exercise pressor reflex. We recently showed in isolated dorsal root ganglion (DRG) neurons innervating the gastrocnemius muscles that two μ opioid receptor agonists, namely endomorphin-2, and oxycodone, potentiated the sustained inward ASIC3 current evoked by acidic saline (pH 6.0). This in vitro finding prompted us to investigate whether endomorphin-2 and oxycodone, when infused into the arterial supply of freely perfused contracting hindlimb muscles, could potentiate the exercise pressor reflex. We found that infusing endomorphin-2 and naloxone (a μ opioid receptor antagonist) into the superficial epigastric artery of decerebrated unanesthetized rats potentiated the peak and integrated pressor responses to static contraction of the triceps surae muscles. The opioid-induced potentiation of the pressor responses to contraction were prevented by infusion of APETx2, an ASIC3 antagonist. Specifically, the peak pressor response to contraction averaged 19.3 ± 5.6 mmHg for control (n=10), 27.2 ± 8.1 mmHg after naloxone and endomorphin-2 infusion (n=10), and 20 ± 8 mmHg after APETx2 and endomorphin-2 infusion (n=10). Infusion of endomorphin-2 and naloxone did not potentiate the pressor responses to contraction in ASIC3 knockout rats (n=6), averaging 21.5 ± 7.7 mmHg for control (n=6), 20 ± 6.2 mmHg after naloxone and endomorphin-2 infusion (n=6), and 19.8 ± 6.9 mmHg after APETx2 and endomorphin-2 infusion (n=4). Similar findings were observed when oxycodone was substituted for endomorphin-2. Specifically, the peak pressor response to contraction averaged 24.3 ± 8.9 mmHg for control (n=10), 33.9 ± 10.6 mmHg after naloxone and oxycodone were infused (n=10), and 26.8 ± 8.1 mmHg after APETx2 and oxycodone were infused (n=10). Altogether, our data strongly suggest that ASIC3 stimulation by mu opioid agonists can potentiate the exercise pressor reflex, provided that mu opioid receptors on group III and IV afferents are not operative. (Supported by HL156594 and HL 156513). HL156594 and HL 156513. This is the full abstract presented at the American Physiology Summit 2024 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.
Modulation of TNF Release by the Innate Fear Odorant 2-Methylthiazoline Requires TRPA1-Mediated Signaling
Authors: Hepler Tyler D. , Tynan Aisling , Hashimoto Okito , Tracey Kevin J. , Chavan Sangeeta S. 
Published: May 2024

The innate fear odorant 2-Methylthiazoline (2-MT) elicits highly robust innate fear and defensive behaviors, such as freezing, hypothermia and bradycardia via activation of transient receptor potential ankyrin 1 (TRPA1) channels. Activation of TRPA1-expressing vagus nerve fibers also regulates IL-1β induced hypothermia and reflex anti-inflammatory responses. However, it is unclear whether 2-MT can trigger an anti-inflammatory response via TRPA1 activation. Here, we demonstrate that 2-MT attenuates endotoxin-induced tumor necrosis factor (TNF) production in wild-type mice in TRPA1-dependent manner. Exposure to 2-MT induces a significant reduction in serum TNF in wild-type mice injected with endotoxin as compared to vehicle control mice (vehicle control vs. 2-MT; 1,123 ± 32.3 pg/mL vs. 714.1 ± 58.2 pg/mL; * p=0.02). However, 2-MT exposure fails to suppress endotoxin-induced TNF-release in TrpA1-knock out mice (vehicle control vs. 2-MT; 1,123 ± 32.3 vs. 948.7 ± 99.2 pg/mL; ns p=0.89). A single exposure to 2-MT during endotoxin injection also protects animals from lethal endotoxemia and significantly improves survival as compared to vehicle-exposed endotoxemic controls (vehicle control vs. single 2-MT Odor; 26.7% vs. 66.7% survival 120 hours post LPS injection). In addition, significant improvement in disease activity is observed in mice exposed to 2-MT odorant (vehicle control vs. single 2-MT Odor; disease activity: 0.5 ± 0.2 a.u. vs. 0.3 ± 0.1 a.u., * p=0.01). Collectively, these data characterize the anti-inflammatory effcacy of 2-MT and demonstrate that the modulation of TNF release by 2-MT requires TRPA1-mediated signaling. This work is supported in part by grants from NIH, NIGMS, 1R35 GM118182 to KJT and 1R01AR083159-01 to SSC. This is the full abstract presented at the American Physiology Summit 2024 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.
High-Fat Diet Alters Neuronal Activity in Cardiometabolic-Regulatory Brain Regions in a Sex-Specific Manner
Authors: Lucas Lillia , Tanner Jordan , Keller Bailey , Bingaman Sarah , Silberman Yuval , Arnold Amy 
Published: May 2024

Obesity is a major public health problem that is associated with dysregulation of central nervous system circuits controlling cardiovascular and metabolic functions. High-fat diet (HFD)-induced obesity in animal models is known to widely influence neuronal function in metabolic-regulatory brain regions; however, the impact of HFD, and its interactions with sex, on neuronal activity in cardiovascular-regulatory brain regions is not fully understood. Thus, the objective of this study was to investigate differences in c-fos expression, a marker of neuronal activity, in key brain regions involved in cardiometabolic regulation in HFD-induced obese mice. We hypothesized that HFD would alter the pattern of neuronal activity in hypothalamic and brainstem regions in a sex-specific manner. To test this, male and female C57Bl/6J mice (n=6/group) were placed on a 60% HFD or matched control diet for 14 weeks. At the end of the diet period, brains were collected to assess for c-fos immunoreactivity in the paraventricular nucleus (PVN) and arcuate nucleus (ARC) of the hypothalamus, as well as in the nucleus of the solitary tract (NTS) and rostral ventrolateral medulla (RVLM) of the brainstem. Brain slices were imaged using a Keyence Fluorescent Microscope and c-fos positive cells were counted using QuPath software in a blinded manner. There was a significant effect due to a sex-by-diet interaction in all brain regions, with female mice having a lower number of c-fos positive neurons compared to males overall, and even more so under HFD conditions (PVN: 132±21 male control vs. 183±28 male HFD vs. 136±21 female control vs. 89±10 female HFD, Pdiet=0.916, Psex=0.041, Pint=0.028 two-way ANOVA; ARC: 92±23 male control vs. 108±16 male HFD vs. 90±7 female control vs. 41±6 female HFD, Pdiet=0.272, Psex=0.024, Pint=0.039; NTS: 72±20 male control vs. 114±115 male HFD vs. 68±10 female control vs. 31±6 female HFD, Pdiet=0.885, Psex=0.004, Pint=0.009; RVLM: 59±12 male control vs. 105±11 male HFD vs. 59±12 female control vs. 28±5 female HFD, Pdiet=0.464, Psex=0.002, Pint=0.002). Overall, these data suggest there are sex-specific differences in neuronal activity within key brain regions integral to cardiometabolic control, which may be influenced by HFD in females. Future studies will need to assess the importance of these changes in neural activity to functional outcomes under normal conditions, and in the context of obesity. Funding: NIH R01 HL156986. This is the full abstract presented at the American Physiology Summit 2024 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.