bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological Functions of Aquaporin-3 in Mediating Water and Solutes
Authors: Ying Yi , Yang Baoxue
Published: May 2024

Aquaporins (AQP), are a family of membrane channel proteins that facilitate the transmembrane diffusion of water and some small non-charged solutes such as glycerol and urea by osmosis or solute gradient. AQP3, an aquaglyceroporin, is expressed in the kidney, skin, and testes, etc. Mice lacking AQP3 have symptoms of diabetes insipidus. In addition, the absence of AQP3 leads to dry skin in mice. AQP4 is permeable to water only. To understand the specific function of the water permeability and small solute transport mediated by AQP3, we generated AQP3 knock-out (AQP3 KO) mice and AQP4 knock-in mice (AQP4 KI) with AQP4 replacing AQP3 in situ. In the basal condition, knock-out of AQP3 in mice led to increased urine volume, decreased urine osmolality and tubule dilation. Interestingly, in AQP4 KI mice, these phenomena were reversed, showing improved urine concentration and tubular morphology. However, there was no significant difference in non-urea solute concentrations between both genotypes. Subsequently, we conducted acute urea loading tests and high-protein diet experiments to further increase the production and excretion of urea in mice. The experimental results showed that both urea loading and high-protein diet had little impact on urine osmolality and urinary urea concentration in AQP3 KO mice. But the urine osmolality and urinary urea concentration in AQP4 KI mice were altered by exogenous administration of urea. Our data indicates that the absence of AQP3 prevents urea accumulation in the kidney, disrupting urine concentration mechanism. The knock-in of AQP4 can restore AQP3 mediated water channel function and help to regulate the urine concentration ability. The water permeability, other than solute transport, of AQP3 plays important role in urine concentrating mechanism. AQP3 KO mice exhibited significant epidermal thickening, excessive keratinization, decreased skin hydration and elasticity. The replacement of AQP4 in situ did not improve these phenomena, indicating that solute transport mediated by AQP3 may play a role in maintaining normal skin function. Therefore, we constructed a mouse model of psoriasis induced by imiquimod (IMQ). It was found that AQP3 expression was reduced in the lesional skin of wildtype (WT) mice, while AQP3 KO mice and AQP4 KI mice exhibited dry skin, excessive epidermal proliferation, and increased inflammatory response. Local treatment with urea (10%) could alleviate these symptoms. These experimental results confirmed the important role of AQP3 in the pathogenesis of psoriasis and the potential role of urea in the treatment of psoriasis. Our study suggests the diverse physiological functions of AQP3 in different tissues.

This research was supported by Beijing Natural Science Foundation (7232249).

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.
Changes in Tryptophan Hydroxylase 2 and 5HT1A Receptor Density May Contribute to Developmental Variation in Response to Serotonin in the in vitro Bullfrog Brainstem
Authors: Billman Tyler , Bellisle Kelsi , Meyer Grace , Brundage Cord
Published: May 2024

Bullfrog, Lithobates catesbeiana, is a vertebrate animal model that can be used to study toxicology and developmental physiology. Our research is focused on better understanding vulnerability to brainstem respiratory centers in the pathology of sudden infant death syndrome (SIDS). We propose that a link between nicotine exposure during development leads to changes in the serotonergic signaling cascades of respiratory coordinating neurons. Caudal raphe neurons send serotonergic fibers that arborize and terminate directly on or near respiratory neurons in the brainstem. In bullfrogs, serotonin elicits a developmentally dependent effect on respiratory motor output. Late metamorphic tadpoles demonstrate an increase in lung burst activity with exposure to low concentrations of serotonin (≤ 0.5μM 5-hydroxytryptamine; 5-HT) mediated in part by 5-HT1a receptor (5HT1aR) activation. This developmental change in activity may be due to changes in the number of serotonergic fibers and/or 5-HT1a receptor density. Using the NIH Basic Local Alignment Search Tool (BLAST) we compared human and bullfrog 5HT1aR and tryptophan hydroxylase 2 (TH2) protein sequences and found a 34 and 65 percent identity match respectively. Quantitative western blot analysis of both proteins indicates developmental shifts in the serotonergic network during metamorphosis. These results were supported by immunohistochemical staining of 5HT1aR and TH2 in caudal raphe containing brainstem sections from pre-metamorphic tadpoles and post-metamorphic frogs. Impairments in the maturation of this serotonergic network may underlie the toxidrome associated with developmental nicotine exposure and further support the increased risk of SIDS following that exposure.

This research was supported by the University of Wisconsin- La Crosse (UWL) through support from the UWL College of Science and Health, two UWL Undergraduate Research Creative Grants and a UWL FY23/24 Faculty Research Grant.

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.
Epigenetic Memory of Intestinal Epithelial Cells in Inflammatory Bowel Disease
Authors: Hamdan Feda , Gonzalez Michelle , Chiang David , Klatt Emily , Fedyshyn Yaroslav , Kossick Kimberlee , Sagstetter Mary
Published: May 2024

Background: The pathogenesis of human Inflammatory Bowel Disease (IBD) is a multifactorial process including interaction between immune, epithelial, and environmental factors. Growing evidence suggests that epithelial cell defects play major role in the pathogenesis of IBD. Epigenetic memory involves lasting, cell-type specific modifications to chromatin at multiple scales, which impacts transcriptional programs required for normal cell functions. A major gap in knowledge are the mechanisms involved in establishing and maintaining memory in cell types and diseases of the intestine. The objective of this study was to determine if intestinal epithelial cells (IECs) retain a memory of altered chromatin architectures and resultant regulation following inflammation. The hypothesis was that the IECs would show lasting altered chromatin structure landscapes (epigenetic memory) in response to inflammation. Methods: We have developed a multicellular model system of IBD using adult stem cell derived organoids from humans with IBD, from regions of the colon with and without active inflammation. We performed ATAC-seq, bulk RNA-seq and single cell RNA-seq on these organoids derived from the uninflamed and inflamed tissues of IBD patients, specifically Ulcerative Colitis (UC). Results: Regions of increased chromatin accessibility are enriched in organoids derived from areas of inflammation in UC patients compared to organoids from patient-matched, uninflamed regions. These open chromatin regions are associated with proinflammatory genes, with modest transcriptional alterations, pointing to an epigenetic inflammatory memory. Motif analysis for accessibly peaks in UC showed an enrichment of the AP-1 family of transcription factors and chromatin remodelers (SMARCA4). This data is consistent with other studies of inflammatory memory from other epithelial cell types, but we show this for the first time in IECs in the context of IBD. Conclusions: This study presents a novel line of investigation and development of model systems to examine epigenetic memory of IECs in human IBD. We expect that our studies will identify new chromatin-based mechanisms of IEC function that are impacted by inflammation.

This research was funded by American Gastroenterological Association Research Scholar Award and KL2 Scholar Career Development Award (KL2 TR002379, National Center for Advancing Translational Science).

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.
Divergent NMJ Development Supports Female Vocal Suppression in the Zebra Finch Songbird (Taeniopygia guttata)
Authors: Gogola Joseph , Margoliash Daniel , Kasthuri Narayanan (Bobby)
Published: May 2024

Songbirds have long been central to the study of vocal learning and production, and in most species, males and females sing. However, in the best-studied species, the zebra finch ( Taeniopygia guttata), only males sing. Most theories of this sexual dimorphism had suggested that male zebra finches have specializations, e.g. to promote song, that females do not. We recently found the opposite. At the synapses that connect motoneurons to muscle fibers (neuromuscular junctions; NMJs) of the avian voicebox (syrinx, analogous to larynx), we found female synaptic specializations that support song suppression: Female syrinx, and only female syrinx (not tongue, latissimus dorsi, or any male muscle measured) has specialized NMJs that could work to suppress singing ability in this species. Specifically, the female syrinx shows a high proportion of putatively weaker en grappe NMJs, biased towards smaller and weaker muscle fibers, which fail to form a motor endplate band (MEB). However, these results raise an unanswered question: are male and female syringes born differently, or do they have divergent developmental programs? We analyzed males and females (n=3) across critical ages - the robust onset of sensory song learning (post-hatch day P30), song-like vocalizations (P50), and the end of sensorimotor learning (P70). We find that NMJs in male and female syrinx muscles are similar early in development and diverge around the age that vocal behavior becomes sexually dimorphic, approaching their different adult phenotypes by the end of this learning phase. We find that outside the MEB, en grappe NMJs are pruned away in males, while en plaque NMJs are lost here in females. Additionally, these NMJ features are highly labile in development, as there are many examples of NMJs intermediate between the vertebrate-typical en plaque and the less well-described en grappe, implying some transitory nature of NMJ class. Preliminary work using developmental hormonal manipulations, which induces sex-reversal of vocal behavior (i.e., promoting female song, or suppressing male song), indicates the en grappe NMJs specifically outside the MEB are most directly tied to vocal ability. Interestingly, the songbird syrinx lacks the tonic muscle fibers on which en grappe NMJs are typically found in mammals, opening the question of the functional attributes of these NMJs. Future work aims to characterize the physiological properties of these putatively weaker synapses, as well as their functional consequences to vocal sexual dimorphism.

NSF-GRFP awarded to JVG; Neuronex awarded to NBK.

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.
Activation of BKα channel provented uremic cardiomyopathy by attenuating oxidative stress
Authors: Bian Shuyang , Liu Zimeng , Luo Xiaomao , Hassounah Faten , Yue Qiang , Park Jeanie , Calvert John W.
Published: May 2024

Background: Uremic cardiomyopathy and renal fibrosis contribute to chronic kidney disease (CKD)-induced morbidity and mortality. Our previous study found that activation of the large conductance calcium-activated potassium channels (BK channels) attenuated renal fibrosis in mice (Wang et al, Kid Int, 2021). We hypothesized that upregulation of BK channels would suppress cardiac fibrosis in CKD. Methods: CKD mice were induced by 5/6 nephrectomy. To upregulation of BKa channels, BMS-191011 (10 mg/kg BW) was given by IP injection every day for 6-8 weeks. Single channel recordings were used to analyze the activation of BKa channel. Blood pressure was measured by non-invasive photoplethysmography using the tail-cuff method. Echocardiogram was used to assess cardiac function. Cultured H9C2 cardiac myoblasts were used to detect the impact of BK opener (NS1916 20mM) on fibrosis markers and oxidative stress. The mRNA expression of BKa in heart was assayed by qPCR. The Hydrogen peroxide (H2O2) was tested by Amplex Red Hydrogen Peroxide Kit. DHE (Dihydroethidium) was assayed to detect superoxide. Superoxide Dismutase (SOD), a defense of oxidative enzyme, was measured using colorimetric activity kit. Results: The expression of BKa mRNA and protein were decreased and cardiac fibrosis was increased in the heart of CKD mice. Single channel recordings showed that human uremic serum (User) attenuated the activation of BKa channel. Upregulation of BKa channel by BSM-191011 decreased the CKD-induced increase in systolic and diastolic blood pressure. Echocardiogram showed that LV end-diastolic dimension increased in 5/6Nx mice, but back to normal after BK opener treatment. Ejection fraction also improved by this treatment. Fibronectin and vimentin were also significantly increased in CKD heart, whereas BMS treatment attenuated the amount of both proteins. In cultured cardiac myoblasts, User and TGFβ increased fibronectin and collagen I, which were in a dose-dependent manner. BKa openers (NS1916) limited the User and TGF-induced upregulation of both proteins in H9C2 cells. User also significantly increased H2O2 and superoxide production in cultured H9C2 cells. Activation of BKa significantly abolished this upregulation. In addition, User and TGFβ decrease SOD production, NS1916 blocked this decline in a dose dependent manner. Conclusions: Activation of BK channel in CKD animals attenuates cardiac fibrosis likely through reduction of uremia-induced oxidative stress. This study could provide new approaches for developing therapeutic strategies for treating uremic cardiomyopathy in chronic kidney diseases.

the Department of Veteran Affairs MERIT Award 5I01BX000994 to HC.

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.
NKCC1-dependent K+ influx inhibits NLRP3 inflammasome activation and prevents intestinal epithelial cell injury
Authors: Koumangoye Rainelli , Delpire Eric
Published: May 2024

Background: Loss of function mutations in SLC12A2, the gene encoding the Na+-K+-2Cl− cotransporter (NKCC1) are associated with autoinflammatory and severe chronic inflammation in multiple organs. NLRP(s) are a family of cytosolic sensors that initiate the innate immune response. Once activated, NLRP(s) form inflammasomes, which are multi-protein complex that sense danger signals, damaged and infected cells. Assembly of the inflammasome mediates caspases-1 activation and the production of the proinflammatory cytokines IL-1β and IL-18 and initiates an inflammatory cell death process called pyroptosis. Aberrant activation of NLRP3 and other inflammasomes leads to a variety of autoimmune and chronic inflammatory diseases. Here we ask whether loss of NKCC1 function affects inflammasome activation in intestinal epithelial cells. Methods: Wild-type intestinal epithelial cells (IEC) and CRISPR/Cas9 NKCC1-deleted clones were tested for inflammasome activation. WT and NKCC1-deficient clones were treated with nigericin, ATP or ouabain to activate the inflammasome. Conditioned media, whole cell lysate and fixed cells were collected at different time points and analyzed by immunoblotting, immunofluorescence, and ELISA (to measure cytokine release). Inflammasome-induced pyroptosis was assessed by measuring LDH release in the supernatant and gasdermine D cleavage by immunoblotting. Results: Loss of NKCC1 function induces inflammasome activation by increasing IL-1β secretion in intestinal epithelial cells. Prolong inflammatory cytokine secretion led to increased pyroptosis-mediated cell death. Loss of NKCC1 mediates NLRP3 inflammasome activation by compromising K+ influx. NLRP3 agonists increase the interaction and localization of WNK1 and SPAK kinases with the NLRP3 inflammasome complex. Conclusions: NKCC1 regulates inflammatory cytokines secretion. Loss of NKCC1 inhibits K+ and Cl− inward fluxes, which in turn activate NLRP3 inflammasome. Loss of NKCC1 function is a previously unknown mechanism that causes aberrant inflammasome activation.

GM118944 DK093501.

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.
Arginyl-tRNA protein transferase 1 (ATE1) regulates protein degradation by Arg/N-end rule pathway
Authors: Frayre Priscila , Alkhatabeh Mosleh , Brower Christopher , Na Elisa
Published: May 2024

Previous studies have shown that deletion or downregulation of ATE1 can lead to neurodegeneration, behavioral abnormalities, hyperphagia and lower body weight. To determine how loss of ATE1 affects energy metabolism and food intake, ATE1-deficient and ATE1-containing mice were given high fat diet for 12 weeks. Based on our current data, we found significant sex differences in body weight and food intakes, with ATE1-deficient mice less sensitive to the obesogenic effects of high fat diet even while consuming the same amount of high fat diet as controls. Interestingly, ATE1-deficient mice exposed to high fat diet displayed lower plasma leptin levels. Leptin-treated ATE1-deficient mice show changes in pSTAT3 expression in the arcuate nucleus of the hypothalamus relative to leptin-treated ATE1-containing mice. Lastly, diet-induced obesity can be ameliorated by tamoxifen-induced knockout of ATE1 in adult male mice relative to vehicle-treated WT mice. Taken together, these data indicate that loss of ATE1 produces attenuated leptin levels in mouse models of diet-induced obesity and can mitigate the effects of high fat diet.

NIGMS, 1SC1GM144190-01 (ESN), NINDS R15NS095317 (CSB), Texas Woman's University internal funds.

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.
γδ T Cells Mediate Pressure Overload-Induced Cardiac Inflammation, Hypertrophy, Heart Failure Development, and Heart Failure Progression
Authors: Bhattarai Umesh , He Xiaochen , Pan Lihong , Niu Ziru , Wang Dongzhi , Chen Yingjie
Published: May 2024

Gamma delta T cells (γδ T cells) are T cells that have a γδ T-cell receptor (TCR) on their surface. γδ T cells display broad functional plasticity following recognition of infected or injured cells by production of cytokines and chemokines, and cytolysis of the infected or injured cells. However, the role of γδ T cells in heart failure (HF) development and HF progression is unknown. To investigate the role of γδ T cells in HF development and progression, we studied the effect of transverse aortic constriction (TAC) on cardiac inflammation, hypertrophy, and dysfunction in both wild type and TCRδ gene deficient (TCRδ−/−) mice, as TCRδ−/− mice have no γδ T cells. Interestingly, TCRδ−/− significantly attenuated TAC-induced left ventricular (LV) hypertrophy as evidenced by less increase of LV weight and its ratio to bodyweight or tibial length. TCRδ−/− also significantly attenuated TAC-induced increase of lung weight, right ventricular weight, and their ratio to bodyweight or tibial length. TCRδ−/− also significantly reduced TAC-induced decease of LV ejection fraction and LV fractional shortening, and LV dilatation. Furthermore, TCRδ−/− significantly attenuated TAC-induced LV cardiomyocyte hypertrophy, fibrosis, and immune cell infiltration. Moreover, we found that TCRδ−/− significantly reduced TAC-induced infiltration and activation of pulmonary antigen presenting cells, CD4 T cells and CD8 T cells. Together, these data indicate that γδ T cells exert an important role in promoting systolic overload-induced cardiac inflammation, HF development, and HF progression.

This work was supported by NIH research grants R01HL161085, R01HL139797, P20GM104357, and P30GM149404.

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.
Alterations in food preference and stress reactivity in mice with a knockout of MeCP2 in POMC neurons
Authors: Randel Hudson , Frayre Priscila , Na Elisa
Published: May 2024

Methyl-CpG binding protein 2 (MeCP2) is an epigenetic factor associated with the neurodevelopmental disorders Rett Syndrome and MECP2 duplication syndrome. Previous studies have demonstrated that knocking out MeCP2 globally in the central nervous system leads to an overweight phenotype and hyperphagia, however it is not clear if the hyperphagia is the result of an increased motivation to obtain food reward or enhancements in food preference. Here, we show that mice deficient in MeCP2 specifically in pro-opiomelanocortin (POMC) neurons have an increased preference for high fat diet but do not have a greater motivation to obtain food reward, relative to wildtype (WT) littermate controls. We also demonstrate that POMC-Cre MeCP2 knockout (KO) mice have increased body weight after long-term high fat diet exposure as well as elevated plasma leptin and corticosterone (CORT) levels compared to wildtype mice. Given that our POMC-Cre MeCP2 KO mice have elevated CORT, we wanted to determine if our KO mice also respond differentially to early life stress such as maternal separation stress compared to WT controls. Collectively, our data suggest that POMC-specific loss-of-function Mecp2 mutations leads to dissociable effects on the rewarding/motivational properties of food as well as changes to hormones associated with body weight homeostasis and stress and could underlie differential behavioral responses to early life stress.

NIGMS 1SC1GM144190-01 (ESN), Texas Woman's University internal funds.

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.
The loss of the hormonal function of bilirubin induces adiposity in male and female mice
Authors: Kipp Zachary , Martinez Genesee , Taylor Lucy , Anderson Christopher , Hall John E. , Stec Donald , Morris Andrew
Published: May 2024

The prevalence of obesity and its related comorbidities, including diabetes and metabolic dysfunction associated fatty liver disease (MAFLD), are on the rise globally, indicating the importance of new therapeutics for these diseases. Interestingly, serum bilirubin levels are negatively correlated with obesity, diabetes, and MAFLD. We have previously generated pegylated bilirubin nanoparticles (PEGBR) and demonstrated their therapeutic potential in the treatment of obesity and MAFLD. However, it’s unknown whether their beneficial effects are due to bilirubin’s antioxidant properties or its hormonal function by binding to and activating the nuclear receptor peroxisome proliferator-activated receptor alpha (PPARa). To determine this, we used female and male hepatocyte-specific PPARa knockout mice ( PparaHepKO) and floxed ( Pparaflox) control mice on a high-fat diet for 30 weeks to induce adiposity and MAFLD. The mice were treated with vehicle or PEGBR (30 mg/kg) for six weeks. In female Pparaflox mice, PEGBR significantly lowered body weight, but not in the female PparaHepKO mice. A similar trend was seen in the male Pparaflox mice but was not statistically significant. PEGBR significantly reduced hepatic fat mass and triglycerides in the female and male Pparaflox mice but not in the PparaHepKO mice. Using lipidomics, we determined the lipid composition of the liver and how PEGBR changed it. In the male Pparaflox mice, PEGBR significantly reduced 109 lipid species, whereas, in the male PparaHepKO mice, PEGBR only reduced 7 species (93.6% reduction). In the female PparaHepKO mice, there was a 2.7% reduction in the number of lipid species significantly decreased by PEGBR compared to Pparaflox controls. Male Pparaflox mice had an increase in plasma high-density lipoprotein cholesterol and a decrease in very-low-density particle number with PEGBR, but this was not seen in the male PparaHepKO or female mice. In addition to protecting against the development of MAFLD, PEGBR significantly reduced fasting blood glucose and insulin levels only in the Pparaflox mice. Overall, the data indicates that the protective effects of bilirubin on obesity, MAFLD, and glucose tolerance are due to its hormonal function through PPARa. This study also confirms the therapeutic potential of bilirubin nanoparticles for obesity and its associated comorbidities.

This work was supported by the National Institutes of Health F31HL170972 (Z.A.K.) and R01DK121797 (T.D.H.J.) and R01DA058933 (T.D.H.J.).

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.
Septin4 Promotes Fibrosis In The Heart After Pressure Overload
Authors: Araujo Natalia , Yücel Doğacan , Smith Calvin , van Berlo Jop H.
Published: May 2024

Background: In response to cardiac injury, the heart undergoes a remodeling process, which may be defined by a complex set of genomic, expression, molecular, cellular and interstitial changes, which can become maladaptive and contribute to the development of heart failure (HF). One of the most important components in cardiac remodeling is the development of fibrosis, which is characterized by excessive deposition of extracellular matrix (ECM) proteins by cardiac fibroblasts, which disrupts the myocardial architecture and function, thus predisposing the progression of cardiac diseases to HF. The small GTPase Septin4 (Sept4) has been described to regulate regeneration and apoptosis in several organs. However, the role of Sept4 in regulating the cardiac stress response is unknown. The present study was designed to investigate if Sept4 would be mediating the alterations associated with cardiac remodeling induced by cardiac pressure overload. Hypothesis: We hypothesized that Sept4 deletion prevents the fibrotic response associated with cardiac remodeling, and the development and progression of HF triggered by transverse aortic constriction (TAC). Methods: 10-week-old wild type (WT) and Sept4 knockout (KO) mice were subjected to TAC to induce cardiac pressure overload. Functional and molecular analyses on WT and KO hearts were performed either at baseline, 1- or 4-weeks post-injury timepoints. Results: After TAC injury, WT mice showed a significant reduction of cardiac function and the development of heart failure, while KO mice were able to maintain normal cardiac function. KO hearts exhibited decreased levels of cardiac ECM deposition and fibrosis compared with WT hearts. Furthermore, KO hearts were more compliant and demonstrated improved end diastolic pressure compared with their WT counterparts. The differentiation of fibroblasts into myofibroblasts was impaired in KO hearts compared with WT controls, which appeared to be associated with attenuated TGF-β-triggered signaling pathway in KO hearts after TAC injury. In line with these findings, we verified in cultured cardiac fibroblasts (CFBs) that Sept4 deletion resulted in reduced myofibroblasts differentiation and a blunted ability of CFBs to contract. Conclusion: Our results demonstrate that Sept4 is an important regulator of ECM remodeling in the heart. Sept4 deletion leads to reduced levels of cardiac fibrosis and attenuation of pressure overload-induced cardiac dysfunction. These findings highlight Sept4 as a potential target to prevent fibrosis in cardiac stress response.

This study was supported by grants from the National Institutes of Health (HL155993 and HL160665).

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.
Defining cardiac stability during Langendorff perfusion
Authors: Haski Anika , Salameh Shatha , Roberts Anysja , Haq Kazi , Swift Luther , Posnack Nikki
Published: May 2024

The Langendorff heart preparation is a valuable ex vivo technique for studying cardiac electrophysiology. For the past century it has been used in toxicology studies, drug testing, and disease modeling and has contributed significantly to understanding cardiac physiology, development, and pathological states. This study aimed to investigate the stability and reproducibility of the modern Langendorff heart preparation under various experimental conditions and to establish cardiac metric standards with corresponding exclusion criteria. Isolated hearts were extracted from adult Sprague Dawley rats and retrograde perfused with a modified Krebs-Henseleit buffer. A cohort of isolated hearts were used to establish a control baseline of multiple physiological parameters measured over time (e.g., electrocardiogram, flow rate, electrophysiology, electrical and calcium dynamics). These control baseline values were then compared to hearts exposed to the most common media additives in Langendorff studies (e.g., blebbistatin(−/−), bovine serum albumin, and voltage and calcium indicator dye). Over a three-hour period, cardiac metrics were monitored in stable Langendorff-perfused hearts. The addition of blebbistatin, DMSO or dyes did not change EP or ECG measurements as compared to control baseline. The most significant drift in all the EP values was ventricular effective refractory period (VERP). With or without blebbistatin, VERP increased from 40 to 60ms over the course of three hours. In that time heart rate and flow also decreased slightly. Blebbistatin was associated with an increased action potential duration but did not alter calcium transient duration. It was also observed that 1% circulating bovine serum albumin quenched the rh237 voltage dye signal 80% as measured by signal to noise. Constant pressure Langendorff-perfusion with a crystalloid buffer provides a reliable and reproducible model for cardiac electrophysiology research with a few caveats. The total length of study should be carefully considered to account for adaptations in cardiac physiology during longer perfusion times. As an excitation-contraction uncoupler, blebbistatin reduces motion artifact but delays action potential duration. Although BSA is used to minimize cardiac edema, it interferes with membrane bound voltage dyes. This study sets physiological parameters as a useful guide for future cardiac studies that use the isolated heart as a research model.

American Physiological Society, R01HD108839 to N.G.P.

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.
AAV-GAA Gene Therapy Clears Long Chain Length Neuronal Glycogen in a Pompe Disease Rat Model
Authors: Fuller David D. , Rana Sabhya , Ribas Roberto A. , Shedlock Cameron J. , Larson Reece , Soto Charles M. , Pope Megan K.
Published: May 2024

Pompe disease is due to mutations in the acid a-glucosidase (GAA) gene. GAA protein degrades lysosomal glycogen and dysfunctional or absent protein leads to cellular glycogen accumulation. In recent years, it has become clear that glycogen accumulation in the central nervous system (CNS) needs to be targeted in Pompe disease. However, the standard of care — intravenous enzyme replacement therapy using recombinant GAA does not effectively target the CNS. Here, we investigated the ability of neonatal AAV-GAA therapy to clear neuronal glycogen in the Pompe ( Gaa−/−) rat. On post-natal day one, male Gaa−/− rats received an administration of AAV9-DES-hGAA (1x1014 vector genomes/kg) via the temporal vein injection or sham injection (1xPBS). Rats were euthanized at age 9 months, and spinal cords and the diaphragm muscle were harvested and glycogen biochemistry was evaluated by matrix-assisted laser desorption/ionization mass spectrometry glycogen imaging (MALDI) and immunohistochemistry (GAA antibody). MALDI imaging reveal significant reduction in glycogen accumulation in the cervical spinal cord, and AAV9-DES-hGAA selectively targeting longer glucose chains within glycogen. Immunohistochemistry verified GAA expression in spinal cord neurons of rats treated with AAV-GAA. In the diaphragm muscle, MALDI revealed that the expected increase glycogen in the untreated Pompe diaphragm was associated with a decrease in n-linked glycans, a potential biomarker of the disease. Strikingly, glycogen content and glycans in the AAV-GAA treated diaphragm were indistinguishable from wild type. We conclude the neonatal gene therapy with AAV9-DES-hGAA can drive functionally relevant GAA expression in the adult rat CNS, and also effectively targets the diaphragm.

R01HD052682 (DDF and BJB), R01AG066653 (RCS), R01CA266004 (RCS), R01AG078702 (RCS), RM1NS133593 (RCS), R35NS116824 (MSG).

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.
Oxygen Therapy After Spinal Cord Injury Reduces Spinal Microglial Inflammatory Signalling
Authors: Fuller David D. , Rana Sabhya , Deegan Kyle M. , Thakre Prajwal , Oberto Jose R. , Mitchell Gordon S. , Nikodemova Maria
Published: May 2024

Spinal cord injury (SCI) interrupts blood flow, causing O2 partial pressure near the site of injury to decrease to very low levels. Spinal hypoxia contributes to tissue necrosis and neuroinflammation, leading to secondary injury. The majority of prior O2 therapy studies after SCI use hyperbaric O2 (HBO), and considerable evidence suggests HBO decreases spinal inflammation and neurodegeneration. HBO consists of 100% O2 (hyperoxia), which is easy to implement, at elevated pressure (hyperbaria), which is challenging to implement. Using an adult rat model of cervical SCI (C2 hemilesion), we compared the impact of daily HBO vs. normobaric hyperoxia therapy on the pro-inflammatory profile of spinal microglia isolated via immunomagnetic cell separation. Rats (n=3 per group) were given C2 hemilesion, followed by 14 days of normobaric hyperoxia (100% O2, 1 hour/day) or HBO (100% O2, 3 ATA, 1 hour/day). The C2-C6 spinal cord was harvested for immunomagnetic microglial isolation using CD11b antibodies. We screened pro-inflammatory gene expression with a PCR array (Rat Toll-Like Receptor Signaling Pathway, Qiagen). Both types of O2 therapy impacted suppressed microglial pro-inflammatory gene expression. In particular, subunit expression of the canonical transcription factor orchestrating microglial inflammatory responses, NFkB2, was significantly reduced. Downregulation of NFkB after HBO has been previously reported, but this is the first evidence for downregulation of NFkB after normobaric O2, and the first evidence for a microglia-specific response. Other pro-inflammatory genes with reduced expression after O2 therapy include: Clec4e, IL1β and CD14. Clec4e is as a transmembrane pattern recognition receptor and “necrotic cell sensor”. Thus, Clec4e downregulation after O2 therapy suggests a shift towards reduced necrosis after SCI. These initial results indicate that both HBO and normobaric hyperoxia treatments reduce the spinal microglia pro-inflammatory responses to cervical SCI, possibly leading to increased cell survival.

HL153140 (DDF), HL147554 (GSM), HL149800 (DDF), McKnight Brain Institute (DDF, GSM).

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.
Interleukin-10 supplementation protects against oxalate-mediated injury in mouse kidneys and bone-marrow derived macrophages
Authors: Doamekpor Mary , Kumar Parveen , Zhang Shali , Freeman McKay , Mitchell Tanecia
Published: May 2024

Approximately 10% of the United States population will experience a kidney stone (KS). Dietary oxalate promotes calcium oxalate (CaOx) crystals, which are precursors to CaOx KS. Macrophages rely on Interleukin-10 (IL-10) anti-inflammatory cytokine signaling to phagocytose and remove CaOx crystals. We recently reported that oxalate causes macrophages to become M1-like (pro-inflammatory) as well as have increased Interleukin-6 (IL-6; pro-inflammatory) and reduced IL-10 cytokine secretion. The purpose of this study was to assess the effects of IL-10 supplementation on mouse kidneys and bone-marrow derived macrophages exposed to oxalate. We hypothesized that exogenous IL-10 treatment prevents oxalate-mediated injury in mouse kidneys and bone-marrow derived macrophages (BMDMs). Mice with a C57BL/6 background were fed Hydroxy-L-proline (HLP; an oxalate precursor) for 7 or 14 days ± IL-10 intraperitoneal injections (25 μg/kg for 2 days) before collecting kidneys and BMDMs. Real-Time Quantitative Reverse Transcription PCR, fluorescence assays, and histological analyses were performed. Mice fed HLP had increased IL-6 and M1 macrophage expression in their kidneys over time. These mice also had reduced IL-10 and M2 macrophage gene expression. In contrast, mice fed HLP with IL-10 supplementation had increased M2 macrophage levels as well as reduced inflammation in their kidneys. Consistent with these findings, BMDM isolated from mice fed HLP displayed similar results. These cells also had reduced mitochondrial membrane polarization and lysosomal staining and increased cellular ROS; whereas, exogenous IL-10 treatment protected BMDMs from oxalate mediated injury. These findings suggest that IL-10 signaling may be important for preventing oxalate-induced injury and inflammation in mouse kidneys and BMDMs.

NIH R01 DK129885 (TM).

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.
Ataxia Telangiectasia-Mutated Kinase Deficiency Induces Cardiac Dysfunction with Increased Myocyte Apoptosis and Hypertrophy with Age
Authors: Dinnes Brooke , Foster Cerrone , Singh Krishna , Dalal Suman
Published: May 2024

Background: Heart failure is the leading cause of death globally. The risk for heart disease increases exponentially with age. The incidence of heart disease is approximately 40% in humans that are 40-59 years old. Ataxia telangiectasia-mutated kinase (ATM), a cell cycle protein, controls growth and repair in response to double-stranded DNA damage. Mutations in the ATM gene lead to a multisystemic disease known as Ataxia Telangiectasia (A-T). These individuals exhibit signs of premature aging. A-T heterozygotes make up about 2% of the population and are more susceptible to ischemic heart disease and die 11 years earlier compared to non-carriers. Previous work has shown that ATM deficiency increases myocyte hypertrophy in 4-month-old (young) ATM heterozygous knockout (hKO) mice vs. age-matched wild-type (WT) mice. However, there was no difference in myocyte apoptosis or heart function between the two groups. Hypothesis: It is hypothesized that with age, ATM deficiency induces myocytes apoptosis and hypertrophy, and cardiac dysfunction. Methods: Heart function was measured in young and 14-month-old WT and hKO mice using echocardiography. Cross sections (5 μm) of heart were used to measure myocyte apoptosis and hypertrophy using terminal deoxynucleotidyl transferase nick end labeling (TUNEL) and rhodamine wheat germ agglutinin (WGA) staining, respectively. Results: Heart function, measured by fractional shortening (%FS) and ejection fraction (%EF), remained unchanged in young and 14-month-old WT mice. However, %FS and %EF were significantly lower in 14-month-old hKO mice vs. young hKO and age-matched WT mice. Myocyte apoptosis and cross-sectional area (hypertrophy) were significantly higher in 14-month-old hKO vs. age-matched WT mice. Conclusion: The data indicates that ATM deficiency induces cardiac dysfunction with increased myocyte apoptosis and hypertrophy with age.

This research was supported by Department of Biological Sciences, Undergraduate Research Honors Program, Offce of Research and Sponsored Programs, Department of Biomedical Sciences, and Department of Health Sciences.

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.
Cervical lymphatic vessel dysfunction induced by amyloid-β and in the 5x-FAD mouse model of Alzheimer’s disease
Authors: Polk Felipe , Pires Paulo
Published: May 2024

Alzheimer’s dementia is a multifactorial disease characterized by amyloid-β (Aβ) accumulation in the brain. Aβ clearance occurs partially via meningeal lymphatics into cervical lymph nodes through superficial cervical lymphatic vessels (sCLV), which relies on intrinsic contractions of sCLV. Previous studies showed increased Aβ build up in the brain following ablation of meningeal lymphatics; however, whether Aβ alters sCLV function remains unclear. We hypothesize that sCLV contractile function will be reduced by acute Aβ exposure and in the 5x-FAD mouse model of Alzheimer’s disease. Contractile function of freshly isolated sCLV was assessed using pressure myography. Acute Aβ exposure was achieved by intraluminal incubation of pressurized sCLV with Aβ(1-40) (5 μM) or vehicle for 15 minutes prior to the start of the experiment. Repeated end-diastolic (EDD) and end-systolic (ESD) measurements were used to calculate fractional pump flow (FPF), the product of contractile frequency (FREQ) measured as contractions per minute (Hz), and ejection fraction (EF) calculated as (EDD2-ESD2)/EDD2, at incremental intraluminal pressures ranging from 2 to 10 cmH2O. Statistical differences were determined by two-way ANOVA followed by Sidak correction for multiple comparisons. All data are means ± SEM. In sCLV isolated from 5 months-old males and females C57bl/6J mice, acute Aβ exposure significantly decreased FREQ (Vehicle vs Aβ, n=4 / n=7, p<0.01), without changes in EF (Vehicle vs Aβ, n=4 / n=7, p=0.115) or FPF (Vehicle vs Aβ, n=4 / n=7, p= 0.536). In pressurized sCLV isolated from 5x-FAD mice, when compared to wild-type littermates, we observed a significant reduction in FREQ (Wild-type vs 5x-FAD, n=4 / n=5, p<0.01). No differences were observed in EF (Wild-type vs 5x-FAD, n=4 / n=5, p=0.1224) or FPF (Wild-type vs 5x-FAD, n=4 / n=5, p=0.193). Together, these preliminary data suggest that acute exposure to Aβ(1-40) decreases FREQ of isolated sCLV, a similar effect observed in sCLV isolated from 5x-FAD mice, albeit not reaching statistical power for multiple comparison significance. Consequently, a decrease contractile frequency can contribute to impairments in lymphatic pumping, which to some extent, can be compensated by prolonged filling times, thus leading to increased ejection fraction. In conclusion, we predict that in vivo sCLV contractile function is maintained via compensatory increases in ejection fraction in conditions of exacerbated Aβ production and deposition.

Funding: National Institutes of Health (R01 AG073230) and the Alzheimer’s Association (AARGD-21-850835).

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.
Dietary Fructose Regulates Kupffer Cell Metabolism and Plasticity
Authors: Lodge Mareca , Cottam Matthew , Richard Daniel , Adams Victoria , Liu Xiaojing , Kennedy Arion
Published: May 2024

Over-consumption of fructose in humans have been linked to increased risk of Non-Alcoholic Fatty Liver Disease (NAFLD) and other metabolic diseases. Recent studies have suggested that fructose plays an important role in the development of liver inflammation, fibrosis, and immune cell activation during NAFLD. However, little work characterizes the direct impact of fructose on macrophage infiltration, phenotype, and function in the liver. Our studies demonstrate that chronic fructose exposure induces liver fibrosis and inflammation compared to control and glucose diets . Single cell RNA sequencing (scRNAseq) revealed fructose and glucose reduced Kupffer cells while increasing transitioning monocytes. However, fructose alone significantly increased expression of fibrosis and wound healing associated genes Mmp12, Il1rn, Rsad2, and Gpnmb in Kupffer cells. In vitro studies demonstrated that fructose treated immortalized Kupffer cells (IMKC) metabolize fructose through glycolysis and pentose phosphate pathway (PPP) by stable isotope tracing. Fructose treated IMKC cells showed reduced cell viability and increased Gpnmb, Tnfa, Mmp12, Il1rn, and Rsad2 gene expression. In addition, inhibition of the PPP further increased fructose induced Gpnmb, Mmp12, Il1rn, and Rsad2 in nonpolarized IMKCs. Taken together, fructose decreases cell viability while upregulating wound healing and fibrosis associated genes in Kupffer cells.

This study was funded by the R21 DK128678 National Institute of Diabetes and Digestive and Kidney Diseases to AK.

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.