bluuebunny/crossref_metadata_2025 huggingface dataset:
Dichotomous response to oral citrate in hypocitraturic stone formers
Authors: Lederer Eleanor , Gianella Fabiola , Maalouf Naim
Published: May 2023

Background and Hypothesis: Hypocitraturia is a marker of metabolic acidosis and a risk factor for kidney stone formation. Oral citrate replacement is a mainstay therapy for hypocitraturic nephrolithiasis. We have observed that a subpopulation of hypocitraturic stone formers do not respond to oral potassium citrate (KCit) with the expected increase in urine citrate despite evidence of adherence to therapy as measured by increased urine K, citrate nonresponders (NR). We hypothesize that altered kidney handling of citrate accounts for the failure of oral citrate to result in increased urine citrate. Methods: To study this hypothesis, we compared changes in urine electrolyte excretion before and after citrate administration in citrate responder (R) and nonresponder (NR) stone formers with hypocitraturia and normal kidney function. Net gastrointestinal alkali absorption was calculated by the method of Oh (Urine Na + K + Ca + Mg) – (Urine Cl + P). Results: We identified 7 R and 8 NR with 24h urine assessments pre and post KCit. 7/8 R and 6/8 NR were female and all were White. There were no significant differences in age, weight, BMI, or dose of citrate. Baseline serum K and bicarbonate (24 +/- 3 meq/L) were similar in both groups and did not show significant changes after KCit administration. By design, 24h urine citrate increased significantly more in R (2.2 +/- 1.4 to 8.3 +/- 3.8 meq/d) than in NR (1.9 +/- 1.4 to 2.9 +/- 1.2 meq/d). Urine pH increased in both groups similarly (6.64 to 7.03 NR, 6.6 to 7.06 R) as did 24h urine K. Urine calcium did not change in either group. Ammonia excretion decreased significantly in R but not NR. However, 24h urine titratable acid excretion decreased in both groups. Net acid excretion was higher at baseline in NR and decreased in both groups but to negative levels in R. Interestingly, net gastrointestinal alkali absorption increased similarly in both groups. Conclusions: These findings suggest that R and NR have equivalent gastrointestinal absorption of KCit. NR may have a greater acid burden enhancing kidney citrate reabsorption as suggested by the higher baseline net acid excretion or altered bone utilization of citrate resulting in reduced excretion of a citrate load.

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.
The effect of weight gain on locust jumping kinematics and extensor muscle activity (Schistocerca americana)
Authors: Ringer Christopher , Feller Kate
Published: May 2023

Female locusts (Schistocerca americana) reach sexual maturity between 46 and 52 days after hatching and experience up to three ovigerous cycles. During these cycles, the females undergo a weight gain of up to 40% of their total body mass. However, previous research has shown that gravid female locusts continue to achieve similar jump height and distance during their pre-gravid and inter-gravid conditions. This finding indicates that female locusts might have intrinsic means to detect increases in body mass during gravidity and the capacity to modulate the neuromechanics of their jumping legs to escape predators as successfully as when they were lighter. This prediction contradicts the current understanding of the degree to which locusts can control their escape jumping movements, which are understood to be a fixed all-or-nothing output. We hypothesized that female locusts modulate the contraction time in their femur extensor muscles to augment the power achieved by their jumping legs during conditions of artificial weight gain. We also hypothesized that this degree of control is not performed in male locusts since they do not naturally experience substantial changes in body mass throughout their adult reproductive stage. Fifteen female and nine male locusts were recorded using simultaneous high-speed video capture (1500 frames per second) and bilateral electromyogram (EMG) recordings during evoked escape jumps. Multiple jumps were recorded for each individual, corresponding to different weight gain conditions. The locusts were mounted with an apparatus to hold clay beads representing a range of masses that would increase body weight by 20-50% of their total body mass. 205 jumps were recorded from females, and 128 jumps were recorded from males. The peak angular velocity and acceleration of the jumping legs were calculated using position tracking software (DeepLabCut) and subsequent kinematic analysis of the leg rotation using custom scripts in R. From the femoral extensor muscle EMG recordings, contraction time was calculated from the start of extensor activity to the beginning of tibia rotation from the femur. In comparing male and female locusts, contraction time was plotted as a function of angular velocity and acceleration to demonstrate the relationship between body mass and jump performance. These results parallel ongoing work investigating the relationship between decreased tidal volumes and jumping performance in female locusts and compensation mechanisms related to overcoming these physiological limitations.

Student Research Grant from Union College

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.
BRCA1-mediated DNA repair protects tubular epithelial cells during Acute Kidney Injury
Authors: Silvaroli Josie , Pabla Navjot
Published: May 2023

Acute kidney injury (AKI) is a common clinical syndrome that is associated with adverse short and long- term sequelae. AKI usually occurs in the setting of other disorders, such as sepsis, rhabdomyolysis, and cardiovascular and oncological diseases, where the underlying disease and or associated therapy cause an abrupt loss of renal function. While the underlying pathophysiological mechanisms are incompletely understood, renal tubular epithelial cell (RTEC) dysfunction and cell-death are the hallmarks and the underlying cause of AKI. Recent studies have shown that DNA damage contributes to RTEC dysfunction during AKI. However, due to the technical challenges in studying DNA repair in vivo, it remains unknown if RTECs can repair their DNA during or after AKI. Here we have used a novel DNA repair reporter mouse to demonstrate that functional homologous recombination (HR) mediated DNA repair occurs in RTECs early during the development of Ischemia-reperfusion associated AKI. Importantly, RTEC-specific deletion of HR-linked DNA repair protein, BRCA1 exacerbates RTEC dysfunction and AKI in both male and female mice. Overall, our studies suggest that DNA repair pathways play a protective role during acute kidney injury and are a promising target for therapeutic interventions.

The current study was supported by an American Heart Association Predoctoral Fellowship (AHA-900765) to J.A.S and NIDDK 1R01DK132230 to N.P.

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.
Neuraminidase causes endothelial phosphatidylserine externalization and ADAM17 activation: implications for shedding of insulin receptor and endothelial insulin resistance
Authors: Ferreira-Santos Larissa , Foote Christopher , Gonzalez Juan , Augenreich Marc , Manrique-Acevedo Camila , Martinez-Lemus Luis , Padilla Jaume
Published: May 2023

Endothelial insulin resistance represents a causal factor in the pathogenesis of type 2 diabetes (T2D) and vascular disease, thus underscoring the need to identify molecular mechanisms underlying defects in endothelial insulin signaling. We previously showed that a disintegrin and metalloproteinase-17 (ADAM17) is increased while insulin receptor α-subunit (IRα) is decreased in the vasculature of patients with T2D, leading to impaired insulin-induced vasodilation. We also showed that ADAM17 is a sheddase that targets IRα. Externalization of phosphatidylserine (PS) from the inner to the outer leaflet of cell membranes has been proposed as a pivotal step in the activation of ADAM17. However, whether PS externalization increases ADAM17 sheddase activity and, consequently, shedding of endothelial IRα in T2D is not known. Herein, we hypothesized that neuraminidase (Neu), an enzyme we showed is upregulated in diabetes, leads to PS externalization via activation of Ca2+ influx and subsequent induction of ADAM17 sheddase activity. All reported differences are significant at P<0.05. In support of this hypothesis, we report that Neu and ADAM17 activities are increased in plasma of individuals with T2D, relative to non-T2D subjects. In experiments using cultured endothelial cells, we show that exposure to Neu increases Ca2+ influx and ADAM17 activity. We also find that augmenting endothelial Ca2+ influx using a calcium ionophore (A23187) increases adhesion of lactadherin (a peptide that binds externalized PS) to the surface of endothelial cells, as does treatment with the ADAM17 activator, PMA, which also reduces IRα on the cells. Importantly, overexpression of ADAM17 in endothelial cells reduces IRα in cell lysates and this coincides with a tendency towards increased IRα in the cell culture supernatant, indicative of protein shedding. Collectively, these findings suggest that Neu causes Ca2+ influx in endothelial cells, favoring PS externalization and, consequently, increased ADAM17 activity and shedding of IRα. Hence, inhibition of Neu and ADAM17 sheddase activities should be considered as novel potential strategies to improve endothelial insulin signaling in T2D.

R01HL151384 (to LAML and JP), R01HL153264 (to LAML and JP), and R01HL137769 (to JP).

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.
TRPM8 channel activation induces relaxation in pudendal artery and corpus cavernosum: Can TRPM8 channel be a target to improve diabetic erectile dysfunction?
Authors: Priviero Fernanda , Moraes Raiana , Araujo Fenix , Jesus Rafael , Silva Liliane , Arishe Olufunke , Pernomian Laena , Wenceslau Camilla , Webb Clinton , Silva Darizy
Published: May 2023

Erectile dysfunction (ED) is one of the most common and underestimated complications of diabetes. Previous studies have shown that TRPM8 activation triggers relaxation of internal pudendal arteries (IPA) with increased sensitivity in hypertensive rats. Despite the correlation between ED and diabetes, research on the role of TRPM8 channels in the IPA and corpus cavernosum (CC) in diabetes still needs to be elucidated. We hypothesized that preserved TRPM8 channel function in diabetic mice could be a therapeutic target for the treatment of ED. Male lean and db/db mice were euthanized, and the IPA were mounted on DMT wire myographs and CC were mounted on AVS organ bath for the measurement of isometric force. Concentration-response curves to icilin or menthol (TRPM8 agonists) were obtained. The CC TRPM8 channels expression was evaluated by western blot. Second harmonic generation was used to evaluate collagen deposition in IPA. Data are expressed as mean ± S.E.M of 3-5 mice. Non-linear regression curve was performed, and the maximum response (Emax) was analyzed using Student’s t test (p<0.05). Similar TRPM8 channel expression was observed in the CC from lean and db/db mice. Menthol-induced relaxation of the CC was reduced in diabetic mice (Emax: 105.00 ± 5.00%) compared to lean mice (Emax: 139.44 ± 15.91%) . Relaxant effect induced by icilin and menthol was similar between IPA from db/db (Emax icilin: 95.56 ± 0.86% and Emax menthol: 93.88 ± 2.33%) and lean (Emax icilin: 97.05 ± 0.87% and Emax menthol: 101.10 ± 1.75%) mice. Interestingly, pre-incubation with icilin (10-4M) for 30 minutes decreased the potency of phenylephrine-induced contraction compared to untreated IPA rings in both db/db and lean mice. In the IPA, diabetes decreased the sensitivity to acetylcholine compared to lean. However, the relaxation induced by acetylcholine was not changed by pre-incubation with icilin. Diabetic mice (db/db) IPA tended to have a decrease in arterial collagen content compared to lean mice. Although menthol-induced relaxation of the CC was reduced in diabetic mice, icilin and menthol were able to promote similar relaxation in IPA from diabetic and lean mice. In this way, TRPM8 function was preserved in IPA from diabetic mice. Icilin reduced sensitivity to phenylephrine in IPA from both mice. These data suggest that activation of TRPM8 could be a therapeutic target for the treatment of ED.

SMSNA, NIH (RO1DK132948) and FAPESB

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.
Higher levels of vigorous physical activity are associated with enhanced nocturnal blood pressure dipping
Authors: Ernst Jackson , Gimblet Colin , Nuckols Virginia , Holwerda Seth , Stroud Amy , DuBose Lyndsey , Wooldridge Nealy , Ajibewa Tiwaloluwa , Fiedorowicz Jess , Pierce Gary
Published: May 2023

Introduction: Nocturnal blood pressure (BP) dipping determined from 24-hour ambulatory blood pressure monitoring (ABPM) is associated with reduced cardiovascular disease (CVD) risk. Physical activity lowers the risk of CVD related, in part, to preserved endothelial function and lower aortic stiffness, however the relation between physical activity and nocturnal dipping remains unclear. The objective of our cross-sectional retrospective analysis was to assess the relation between physical activity and nocturnal BP dipping, and whether this relation was confounded by measures of vascular function. We hypothesized that higher levels of physical activity would be associated with greater nocturnal BP dipping. Methods: Healthy adults (n=172, age 19 to 65 years, 55% female) had 24-hour ABPM measured. BP recordings were taken every 30 min during the daytime and every 60 min during the nighttime. Nocturnal “dippers” had a 10-20% difference between their mean daytime and nighttime systolic BP and “non-dippers/inverse dippers” had <10% difference. The modifiable activity questionnaire was used to assess physical activity levels via self-reported days/week with greater than 30 min of moderate activity (3.0-6.0 METs) and vigorous activity (>6.0 METs). Endothelial function (brachial artery flow-mediated dilation, FMD), and aortic stiffness (carotid-femoral pulse wave velocity, cfPWV) were also assessed. Results: Nocturnal BP dippers performed more days/week of moderate and vigorous physical activity compared to non-dippers (P=0.007 and P=0.008, respectively). Both moderate (B=0.386, P=0.042) and vigorous physical activity (B=0.604, P=0.002) were associated with nocturnal BP dipping in univariate linear regression analyses. However, only vigorous activity (B=0.926, P=0.001) remained associated with nocturnal BP dipping after adjustment for age, BMI, 24-hr systolic BP and diastolic BP, brachial FMD and cfPWV. Conclusion: Vigorous physical activity may attenuate CVD risk in part from enhanced nocturnal BP dipping. Future studies should investigate additional mechanisms by which vigorous physical activity may enhance nocturnal BP dipping.

This study was supported by grants from the National Institutes of Health (AG063790; HL014388, HL07121; AG043722). Dr. Pierce is supported by the Russell B. Day and Florence D. Day Endowed Chair in Liberal Arts and Sciences, University of Iowa.

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 exercise prior to a night of partial sleep deprivation on ambulatory blood pressure
Authors: Bommarito Julian , Millar Philip
Published: May 2023

Introduction: Blood pressure (BP) follows a circadian rhythm intertwined with the sleep-wake cycle, dipping during sleep and surging in the morning. Prior work has found that sleeping ≤4.5 hours for one night (i.e., acute partial sleep deprivation [PSD]), can increase ambulatory BP during the night and subsequent day, resulting in increased 24-hour BP - a risk factor for increased mortality. In contrast, a bout of aerobic exercise can reduce ambulatory BP for up to 24 hours, termed post-exercise hypotension. The primary aim of this study is to examine if exercise can attenuate the rises in 24-hour ambulatory BP caused by acute PSD. We hypothesized that exercise would attenuate the elevated 24-hour BP response caused by acute PSD. Methods: Twenty young, healthy adults (22 ± 4 years; 7 males and 13 females; Sleep chronotypes: 4 early, 10 intermediate, and 6 late) completed a randomized crossover trial where they slept normally (sleep: 2300 to 0700 hours), sleep was partially deprived (sleep: 0330 to 0700 hours), or exercise (50-minutes continuous cycling at 70-80% age predicted heart rate maximum) was performed before a night of PSD (sleep: 0330 to 0700 hours). Sleep duration was assessed using self-report and an accelerometer worn on the wrist (wGT3X-BT, ActiGraph). Ambulatory BP (Oscar2, SunTech Medical) was measured in 30-minute intervals over the course of a 27-hour epoch. Results: Acute PSD increased 24-hour systolic (control: 118 ± 9 mmHg vs. PSD: 122 ± 9 mmHg. P<0.001) and diastolic (control: 67 ± 5 mmHg vs. PSD: 70 ± 7 mmHg, P<0.001) BP, but exercise did not blunt these responses (systolic BP: 122 ± 11 mmHg, P=1.0 vs. PSD; diastolic BP: 70 ± 6 mmHg; P=1.0 vs. PSD). Elevations in 24-hour BP were due to elevations in systolic (control: 104 ± 9 mmHg, PSD: 123 ± 12 mmHg, exercise + PSD: 121 ± 13 mmHg, P<0.001) and diastolic (control: 53 ± 7 mmHg, PSD: 71 ± 9 mmHg, exercise + PSD: 71 ± 9 mmHg, P<0.001) BP during the nighttime wakeful period (0000 to 0300 hours). Acute PSD blunted the magnitude of the morning BP surge (control: 24 ± 11 mmHg vs. PSD: 17 ± 8 mmHg , P=0.02) due to elevations in lowest sleep BP (control: 98 ± 7 mmHg vs. PSD: 104 ± 10 mmHg, P=0.007), but exercise did not reverse these responses (morning BP surge: 16 ± 8, P=1.0 vs. PSD; lowest sleep BP: 106 ± 13, P=1.0 vs. PSD). No sex or chronotype differences were observed. Conclusion: These findings suggest that acute PSD has minimal effects on the circadian BP profile in young, healthy adults irrespective of sex and chronotype, and continuous cycling exercise at a moderate intensity is not a sufficient stimulus to attenuate such effects.

This research was supported by a Natural Science and Engineering Research Council (NSERC) of Canada Discovery Grant (P.J.M)

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.
Shear rate patterns during flow-mediated dilation in women with endometriosis: preliminary findings
Authors: Kirby Nathalie , Williams Auni , Content Virginia , Wolf S Tony , Dillon Gabrielle , Stachenfeld Nina , Alexander Lacy
Published: May 2023

Purpose: Endometriosis is an estrogen-dependent gynecological disorder associated with systemic inflammation and arterial stiffness, which may negatively modulate shear stress patterns to promote a pro-atherogenic state, and thus contribute to the elevated cardiovascular disease risk observed in women with the disease. However, shear stress patterns have not previously been examined in this population. Therefore, the purpose of this study was to investigate whether arterial blood flow patterns are altered in women with endometriosis. We hypothesized that women with endometriosis would exhibit disturbed blood flow patterns, characterized by high retrograde shear rates and oscillatory flow as well as reduced anterograde shear rates, as compared with women without the disease. Methods: We examined anterograde and retrograde shear rates, and oscillatory shear index (OSI; |retrograde shear rate|÷[|antegrade shear rate|+|retrograde shear rate|]) in four women with surgically confirmed endometriosis and eight without (mean (SD), 28 (5) years, BMI 24.7 (4.2) kg·m-2) at rest, during hyperemia (60 s post-forearm occlusion at 220 mmHg) and recovery (120-180 s post-occlusion) from flow-mediated dilation using duplex Doppler ultrasound. Shear rates were compared using two-factor (group x phase) linear mixed-effects models with post-hoc corrections for multiple comparisons of three time-points. Results: Endometriosis patients exhibited greater OSI (interaction: p=0.001) at rest (mean difference [95%CI]; 0.095 [0.001, 0.188], p=0.033) and recovery (0.126 [0.034, 0.226], p=0.005), though not during hyperemia ( p>0.999) compared to controls. This was driven by greater retrograde shear (interaction: p=0.013) during recovery (15 sec-1 [2, 28], p=0.002), though retrograde shear did not differ between groups at rest ( p=0.155) or during hyperemia ( p>0.999). Anterograde shear (interaction: p=0.049) was greater in controls than in endometriosis patients during hyperemia (276 sec-1 [61, 613], p=0.026), but not during rest or recovery (both p>0.999). Conclusions: Women with endometriosis exhibited greater oscillatory shear at rest and greater oscillatory and retrograde shear during recovery from flow-mediated dilation, as compared to controls. However, anterograde shear was diminished in endometriosis patients during hyperemia. These data indicate that shear stress patterns are negatively altered in women with endometriosis, which provides novel mechanistic insight into the pathophysiology underlying the associated elevated cardiovascular disease risk.

National Institutes of Health Grant R01 HL161000

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.
The Relationship of Circulating Extracellular Vesicles to Small Vessel Disease in Acute Ischemic Stroke
Authors: Parray Aijaz , Akhtar Naveed , Sivaraman Siveen , Raïq Hicham , Own Ahmed , Shuaib Ashfaq , Agouni Abdelali
Published: May 2023

The association between Extracellular Vesicles (EVs) and Small Vessel Disease (SVD) might aid in the accurate early diagnosis and prognosis of acute ischemic stroke (AIS). This may be crucial for implementing the appropriate care plan and follow-up measures to limit the risk of permanent damage and prevent future occurrences. The purpose of the present study was to investigate the connection between circulating levels of EVs from various cellular origins and AIS severity biomarkers, established risk factors, and the presence of SVD as determined by noninvasive MRI imaging.The count of total circulating medium-size EVs and their phenotyping according to cellular origins were determined by flow cytometry analysis in platelet-free plasma from healthy volunteers and patients with AIS. Then, the relationship between the circulating of EVs to SVD and other risk factors was studied.When compared with controls, AIS patients exhibited a significantly higher number of circulating EVs originating from the endothelial cells, platelets, activated platelets, erythrocytes, and granulocytes. Multinomial logistic regression analysis showed a strong association between increased numbers of EVs derived from activated platelets (CD62P+) and erythrocytes (CD235a+) and the odds risk of AIS. However, it was found that a one-unit increase in CD235a+ EVs is associated with a 0.77-unit decrease in the odds of having SVD. Most AIS patients with SVD had hypertension, white matter ischemia, silent infarct, Basis Pontis ischemia, and cerebral microbleeds. However, the most significant risk for SVD was found in patients with hypertension on admission. Patients with hypertension on admission were 9.33 times more likely to have SVD than patients without hypertension on admission.Our findings underscore the value of circulating EVs as biomarkers of cell activation and thrombosis in AIS. Furthermore, our findings suggest a potential pathophysiological role for EVs in the onset and development of SVD and an interrelationship with major risk factors for AIS such as hypertension. Altogether, the association of EVs and non-invasive MRI imaging assessment of SVD presence may represent a novel combined approach for the identification of individuals with the highest risk of AIS and patients with the highest odds of recurrent stroke.

This study was made possible by Qatar National Research Fund [grant No. NPRP11S-0114-180289]. The statements made herein are solely the responsibility of the authors.

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.
Endothelial beta-globin is differentially expressed across mammalian species
Authors: Hakim Md Abdul , Brooks Steven , Kamenyeva Olena , Kabat Juraj , Solomon Steven , Ford Verity , Davis Jeremy , Ruhl A. Parker , Ackerman Hans
Published: May 2023

Globin proteins interact with endothelial nitric oxide synthase at the myoendothelial junctions of resistance arteries to regulate nitric oxide signaling between endothelium and smooth muscle. Human resistance arteries express both alpha and beta globin to form heterotetrameric hemoglobin (α2β2). To better understand the role of hemoglobin in human resistance arteries, we need to identify an animal model in which both alpha and beta globin are expressed in the resistance vasculature. To identify potential candidates, we used microscopy to survey a range of mammalian laboratory animals for hemoglobin in the artery wall. We isolated arteries (100-200 μm in diameter) from mesenteric tissue collected from human patients undergoing clinically-indicated surgery and from the following laboratory animals: mouse ( Mus musculus, C57BL/6 strain), rat ( Rattus norvegicus, CD strain), African thicket rat ( Grammomys surdaster), guinea pig ( Cavia porcellus), New Zealand white rabbit ( Oryctolagus cuniculus), Beagle dog ( Canis lupus familiaris), and cynomolgus macaque ( Macaca fascicularis) after they underwent euthanasia on approved animal study protocols. We leveraged the autofluorescence of heterotetrameric hemoglobin under multiphoton excitation to visualize hemoglobin in the wall of intact, unstained, paraformaldehyde-fixed artery segments. Autofluorescent puncta representing tetrameric hemoglobin were observed in the wall of resistance arteries from the human patients, non-human primate, and canines, but not from rabbit nor any of the rodent species. The ability of beta globin to restrict endothelial NO signaling was confirmed in canine arteries ex vivo by testing a beta globin mimetic peptide that inhibited vasoconstriction to phenylephrine. In conclusion, primates and canines appear to have tetrameric hemoglobin in the resistance artery wall, whereas rodents and rabbits do not. This study highlights differences in vascular globin expression between humans and rodents and extends the recent discovery of hemoglobin in resistance arteries of humans to two additional mammalian species that may serve as models for studying the unique activities of tetrameric hemoglobin in the resistance vasculature.

Funding: Intramural Research program, NIAID, NIH

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.
Overexpression of regulator of G protein signaling 2 (RGS2) in the paraventricular nucleus reduces blood pressure in angiotensin II-induced hypertensive rats
Authors: Boomer Shane , Liu Xuefei , Zheng Hong
Published: May 2023

The hypothalamic paraventricular nucleus (PVN) is important in mediating sympathetic activity to regulate blood pressure. The regulator of G protein signaling 2 (RGS2) is a negative G protein regulator. RGS2 selectively regulates Gαq signaling, an important cause of hypertension and cardiac hypertrophy. However, little-to-no studies are being done related to G-protein-RGS2 signaling on the central mechanisms of blood pressure control and sympathetic activation. In this study, we hypothesized that central RGS2 overexpression changes blood pressure regulation by decreasing the response to angiotensin II (ANG II). We infused ANG II (200ng/kg/min) via an osmotic minipump to induce hypertension. These rats were outfitted with telemetry and measurements of blood pressure and heart rate over the next 14 days, with or without RGS2 adenovirus (AV) injection into the PVN. We found that days 3, 4, and 6 after virus transfection showed a significant difference between the group outfitted with only the ANG II pump versus those outfitted with both ANG II pumps and PVN AV injection. Results shown below are in order of ANG II pumps only, ANG II pump after AV, and ANG II pump + AV, respectively (unit in mmHg). Day 3: 155.5 +/- 9.4, 131.8 +/- 4.5, 134.3 +/-9.5, P<0.05; Day 4: 164.5 +/- 8.0, 140.3 +/- 7.0, 136.1 +/- 10.2, P<0.05; Day 6: 169.3 +/- 4.2, 144.4 +/- 4.5, 140.6 +/- 8.3, P<0.05. There was no significant difference between day 6 and the end of the experiment. Our real-time PCR and Western blot studies showed punched PVN tissue highly expressed RGS2 mRNA and protein. Further, in vitro study showed ANG II treatment affected RGS2 mRNA and protein expression in cultured hypothalamic neuronal cells. The findings suggest that RGS2 ameliorates ANG II-induced hypertension in rats, possibly via regulating central PVN-mediated blood pressure controlling and sympathetic activation.

Funded by NIH R01-DK-114663 & R01-DK-129311 and USD G-RISE, NIH T32GM-136503.

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.
Acid Ceramidase as a Novel Target for Adiponectin Receptor Agonist to Abrogate NLRP3 Inflammasome Activation and Glomerular Injury during Obesity
Authors: Huang Dandan , Li Guangbi , Zou Yao , Li Ningjun , Ritter Joseph , Li Pin-Lan
Published: May 2023

Adiponectin receptor agonists have recently been reported to protect against glomerular inflammation and injury during obesity. Nevertheless, the molecular mechanism underlying their protective action against obesity-related glomerulopathy (ORG) remains poorly understood. Given the implication of ceramide signaling pathway in the pathogenesis of ORG, the present study tested whether adiponectin receptor agonists target lysosomal acid ceramidase (AC) to inhibit NLRP3 inflammasome activation and glomerular injury during obesity. Confocal microscopy showed that NLRP3 inflammasome activation induced by visfatin, a pro-inflammatory adipokine, in murine podocytes was remarkably attenuated by adiponectin. Also, it was found that adiponectin significantly inhibited visfatin-induced formation of multivesicular bodies (MVBs) containing IL-1β in podocytes. Such inhibitory effect of adiponectin was abolished by AC inhibitors (carmofur and ARN14974) but mimicked by genistein (AC inducer) or MCC950 (NLRP3 inflammasome inhibitor). By nanoparticle tracking analysis, we measured exosomes released from podocytes in different groups, which have been reported to mediate the secretion of NLRP3 inflammasome products to extracellular space to activate inflammatory response. Visfatin-induced elevation of exosome release from podocytes was remarkably suppressed by adiponectin. This action of adiponectin was blocked by AC inhibitors but mimicked by genistein. In vivo, we showed that high-fat diet-induced T cell infiltration in glomeruli was exaggerated by podocyte-specific Smpd1 gene (gene code of acid sphingomyelinase) overexpression in Smpd1trg/Podocre mice compared to WT/WT mice. However, intraperitoneal injection of AdipoRon, a synthetic adiponectin receptor agonist, significantly decreased obesity-induced glomerular inflammatory response in both WT/WT and Smpd1trg/Podocre mice. Such anti-inflammatory effect of AdipoRon was prevented by co-treatment with carmofur. Moreover, podocyte-specific Smpd1 gene overexpression amplified HFD-induced podocyte injury, proteinuria, and glomerular sclerosis in Smpd1trg/Podocre mice compared to control littermates. These pathological changes were prevented by AdipoRon, and the effect of AdipoRon was reversed by carmofur. Taken together, our findings suggest that activation of AC signaling pathway mediates the protective action of adiponectin receptor agonists against glomerular inflammation and injury in ORG.

This study was supported by NIH grants DK054927 and DK120491.

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.
Role of tyrosine phosphorylation of Mfn2 in endoplasmic reticulum-mitochondria coupling
Authors: Chaput Isabel , Kelly Madeline , Landherr Maria , Polina Iuliia , Nieto Bridget , Cypress Michael , Jhun Bong Sook , Zhang Peng , O-Uchi Jin
Published: May 2023

Introduction: A mitochondrial fusion protein, Mitofusin 2 (Mfn2) serves as one of the major components for tethering the mitochondria and endoplasmic reticulum (ER), which regulates the exchange of lipids, Ca2+, and reactive oxygen species (ROS) across the two organelles. Several post-translational modifications (PTMs) of Mfn2 have been identified via mass spectroscopy, such as tyrosine phosphorylation (P-Tyr). However, little information is available whether any PTMs of Mfn2 can regulate mitochondrial and ER tethering function under physiological and pathological conditions. Hypothesis: P-Tyr of Mfn2 regulates Mfn2 function such as ER-mitochondrial tethering. Methods: To achieve stable activation of c-Src, we stably overexpressed c-Src or an shRNA targeting the shRNA targeted to C-terminal Src kinase (CSK), a specific negative regulator of c-Src, in HEK293T cells. Stable cell lines were used for biochemical, cell biological, and physiological assays. Results: Two computational program for phosphorylation site prediction, NetPhos and Group-Based Prediction System, predicted at least five c-Src-specific P-Tyr sites within the Mfn2 structure. Using immunoprecipitation and a phosphate-affinity electrophoresis technique (Phos-tag SDS-PAGE), we found that overexpression of c-Src, but not other Src family members, leads to P-Tyr of Mfn2. Moreover, dephospho-mimetic mutations (replacing Tyr with Phe) in Mfn2 significantly decreased the c-Src-dependent P-Tyr in Mfn2. Stable c-Src activation decreased the distance between the ER and outer mitochondrial membrane (OMM) as assessed by transmission electron microscopy and Förster resonance energy transfer between an OMM-targeted cyan fluorescent protein and an ER membrane-targeted yellow fluorescent protein the ER membrane measured by confocal microscopy. Mitochondrial Ca2+ (mtCa2+) uptake in response to cytosolic Ca2+ elevation increased with faster kinetics under c-Src activation, followed by increased mitochondrial ROS, and decreased oxygen consumption rate. Knocking down of endogenous Mfn2 by stable expression of shRNA targeting 3’ untranslated region of Mfn2 increased the distance between ER and OMM, and decreased mtCa2+ uptake. The reintroduction of wild-type Mfn2 in Mfn2-knockdown cells reversed these changes to the levels observed in cells expressing control shRNA. However, re-expression of a dephspho-mimetic mutant of Mfn2 in Mfn2-knockdown cells failed to rescue the changes in mtCa2+ uptake profile. Conclusion: P-Tyr of Mfn2 by c-Src modulates the distance between the OMM and ER, resulting in mtCa2+ elevation and oxidative stress.

NIH/NHLBI R01HL136757

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.
Core temperature responses in well-healed burn survivors during exercise heat stress: effect of cooling modalities
Authors: Atkins Whitley , McKenna Zachary , Foster Josh , Belval Luke , Orth Bonnie , Johnson Elias , Benning Mayah , Watso Joseph , Hakes Courtney , Jay Ollie , Crandall Craig
Published: May 2023

Introduction: Every year, ~150,000 patients are treated in the United States with burn-related injuries. Previously, our group has shown that ~75% of burn survivors have a maximal aerobic capacity in the lowest 20th percentile rankings, relative to sex and age-adjusted non-burned individuals. This level of impairment is strongly associated with cardiovascular-specific, as well as all cause, morbidity, and mortality. Moreover, burn injuries that require grafting impair thermoregulation, and the subsequent increases in skin and core temperature may dissuade these individuals from engaging in exercise and/or physical activity. Low-energy cooling strategies have potential to attenuate increases in core temperature in burn survivors, which may promote regular physical activity. Thus, the purpose of this study was to evaluate the efficacy of low-energy cooling modalities on thermoregulatory responses during physical activity in the heat. Methods: Twenty-four adults with NO-BURN (n = 9), MODERATE burns (20-40% body surface area burned, n = 7), or LARGE burns (> 40% body surface area burned, n = 8) walked for one hour at a moderate intensity (rate of metabolic heat production of 4.5 W/kg body mass) in an environmental chamber (39°C, 40% RH). Burn survivors were at least 2 years post-injury. Participants performed this activity four times, with the following modalities randomly applied throughout each trial on separate days: no cooling (i.e., control), fan at 4 m/s (FAN), water spray (WS, minimum 10-50 g every 5 min, scaled to burn area size), or WS+FAN. Core temperature (Tcore) was recorded throughout each trial via a telemetric pill. Final Tcore values for each cooling modality were compared against the no cooling condition. Results: For the LARGE burn group, WS reduced end-exercise Tcore by 0.37°C (range 0.09 to 0.66°C) compared with no cooling ( p = 0.01). FAN and WS+FAN did not impact end-exercise Tcore for the LARGE burn group ( p ≥ 0.48). No cooling modality affected Tcore for the MODERATE burn group ( p ≥ 0.12) or the NO-BURN group (p ≥ 0.55). Conclusion: At the assessed workload and environmental condition, the efficacy of the applied cooling modalities on Tcore responses for burn survivors appears to be dependent on both the selected modality and the size of the burn surface area. Namely, WS attenuated the increases in Tcore in participants with LARGE burn injuries, but FAN and WS+FAN did not attenuate Tcore responses in any group.

Supported by NIHGrant R01GM068865

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.
Decreasing FIO2 induces spontaneous intermittent hypoxic events in mice
Authors: Kalra Hardik , Jedlicka Charles , Vasileva Anastasiia , Tomasson Michael , Bates Melissa
Published: May 2023

Chronic intermittent hypoxia, CIH, is a feature of sleep apnea widely used in research to mechanistically examine the physiological effects of sleep apnea. These mechanistic studies commonly utilize mice as the study model. In room air, mice experience periodic apneas and arterial oxygen desaturations. Activation of the carotid body could stabilize breathing and decrease these events. Therefore, we hypothesized that C57BL/6J mice experience fewer hypoxic events with decreasing FIO2.We placed 6 C57BL/6J mice (3 male, 3 female) in an Emka® unrestrained barometric plethysmograph and measured pulse oximetry using the STARR LifeSciences MouseOx® Plus system. The mice were exposed to different levels of FIO2 for 10 minutes each: 0.21, 0.15, 0.12, 0.09, 0.30 ± 0.01. We defined a hypoxic event as 3% deviation from the average oxygen saturation at each FIO2. Mice did not show fewer hypoxic events when exposed to increasing levels of hypoxia. In fact, mice experienced more hypoxic events at 0.15 than 0.21 and 0.30 FIO2 (P<0.05). Mice also experienced more hypoxic events at 0.12 than at 0.30 FIO2. Additionally, we found that hypoxic event nadir SpO2 was significantly lower at all FIO2 levels when compared to 0.21 FIO2. Hypoxic events at all FIO2 levels had significantly lower average SpO2 compared to 0.21 FIO2. No change was observed for average SpO2 for hypoxic events at 0.30 FIO2 relative to 0.21 FIO2. Contrary to our hypothesis, intermittent hypoxic events are not stabilized by exposure to a hypoxic environment. Future work will evaluate this in other mouse strains.

1R56HL152365

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 mental wellness training within advanced exercise physiology courses on student mental health
Authors: Leary Miriam , Bryner Randy
Published: May 2023

Mental illness has become a prevalent health issue among college students. Within rigorous STEM based physiology programs, academic stress can negatively affect overall wellbeing. The objective of this study was to improve mental wellness and stress of undergraduate juniors in a rigorous physiology course by providing wellness trainings from campus clinicians. We hypothesized that a wellness training intervention would improve self-reported mental wellness, academic stress, and overall perceived stress of undergraduate physiology students. Students completed a survey in the first advanced physiology course at midterm in fall (F) 2021 (n=200, 99%). During the second advanced physiology course in the spring 2022 semester, students received six 30 minute wellness trainings delivered by campus counseling clinicians and were reassessed at the same time point in the spring (S) semester (n=170, 94%) as during the fall. Surveys included nonvalidated questions as well as the Perception of Academic Stress Scale and Cohen’s Perceived Stress Scale. Following the wellness intervention, more students felt satisfied with their overall mental health and wellbeing (F 21%, S 41%), and fewer reported feeling anxious (F 89%, S 50%) and depressed (F 58%, S 26%). Students still felt academics were a significant sources of stress (F 96%, S 96%), but were less likely to feel academics negatively impacted their mental health (F 73%, S 47%). While responses improved over time on the Perception of Academic Stress Scale (34.7 ± 8.5 vs. 53.7 ± 11.5, p<0.001), there were no differences on the Cohen’s Perceived Stress Scale (20.0 ± 6.8 vs. 20.6 ± 6.7, p=.0.20). In conclusion, wellness trainings embedded into rigorous physiology courses can positively impact undergraduate physiology students’ mental wellbeing. Potential mechanisms may include learning and practicing stress management techniques for academic stress.

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.
The nigro-vagal modulation of the proximal colon is compromised in a model of environmental Parkinson's Disease
Authors: Xing Tiaosi , Nanni Giorgia , Burkholde Cameron , Browning Kirsteen , Travagli R. Alberto
Published: May 2023

Parkinson’s Disease (PD) is a prevalent neurodegenerative disease characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc), which results in tremor, rigidity and bradykinesia. Up to 80% of the PD patients suffer from constipation about 10 to 20 years before experiencing motor symptoms. We previously reported that a monosynaptic pathway connects SNpc to neurons of the dorsal motor nucleus of the vagus (DMV). This monosynaptic pathway modulates the vagal control of gastric and proximal colon motility, and gastric motility is impaired in an environmental model of parkinsonism, induced by oral administration of subthreshold doses of paraquat (P) and lectin (L) (PMID 30302391). The current study was designed to test the hypothesis that nigro-vagal modulation of the proximal colon is compromised in the oral P+L model of parkinsonism.Proximal colonic motility and tone were recorded in age-matched male rats via a strain gauge aligned with the colonic circular smooth muscle, approximately 3 cm distal to the ileal-cecal valve. Activation of SNpc neurons via microinjection of the ionotropic glutamate selective agonist, NMDA, increased proximal colonic motility (187±52.6% of baseline, n=13; Paired t test, p<0.0001) and tone (323±97.2mg, n=14). In our rat model of environmental parkinsonism, baseline colonic motility (155.2±49.6mg, n=5) showed no change compared to control rats (146.6±67.8mg, n=5; Unpaired t test, p=0.0387), however, the ability of NMDA-induced SNpc activation to increase colonic tone and motility was decreased (tone 303.4±70.8mg, n=5 vs 500.8±207.5mg in control rats, n=5; unpaired t test, p=0.0395; motility 139.8±24.8% of baseline, n=4 vs 222.6±62.9% of baseline of the age matched control rats, n=3; unpaired t test, p=0.0439). Gastro-cecal transit, measured using the 13C lactose ureide-breath test, showed that transit time was increased in parkinsonian rats from 132.7±28 min (n=7) to 218.4±59.4 min (n=11; one-way ANOVA, p=0.0026). Chemogenetic inhibition of the nigro-vagal pathway attenuated the delay in transit in parkinsonian rats to 173.2±16.3 min (n=5; one-way ANOVA, p=0.2886 vs control rats).These data suggest that intestinal transit is delayed, and the ability of the SNpc to modulate proximal colon motility and tone is attenuated in a model of environmental parkinsonism. Impairment of this nigro-vagal pathway may contribute to the severely reduced colonic transit and prominent constipation observed both in patients and in animal models of Parkinson Disease.

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.