Arterial Response Research Articles

Hepatic arterial buffer response in monochorionic twins with selective fetal growth restriction.

Monochorionic twins (MC) have higher risk ofperinatal morbi-mortality compared to singletons and dichorionic twins (DC). Selective fetal growth restriction (sFGR) increases the chances of adverse outcome. Hepatic arterial buffer response (HABR) is an important mechanism for maintaining liver perfusion. We hypothesised that HABR is active in monochorionic diamniotic twins (MCDA) with sFGR where restricted fetus may have liver hypoperfusion. The objective of this study is to test whether the HAV-ratio is diminished in pregnancies affected by selective fetal growth restriction pointing to activation of HABR in the growth-restricted fetus. sFGR was defined according to a consensus definition. Hepatic artery (HA) peak systolic velocity (PSV) was measured and its correlation with fetal Dopplers and pregnancy characteristics were determined. A ratio using HA-PSV (HAV-ratio) was calculated and its association with sFGR was established. Further analysis of HA-PSV was performed comparing z-scores between normal and growth restricted fetuses. We included 202 MCDA pregnancies, 160 (79 %) normal and 42 (21 %) with sFGR. HAV-ratio was significant different between groups. The mean HAV-ratio was 1.01 (±0.20) for normal twins and 0.77 (±0.25) for sFGR. Furthermore, HA-PSV z-scores was significant increased in in growth-restricted fetus (0.94±1.45), while in normal fetuses was-0.16 (±0.97). Our findings demonstrate that, in pregnancies with sFGR, HAV-ratio is significantly lower than in normal MCDA pregnancies. The lower HAV-ratio is due to an increase in HA PSV in the growth restricted fetus. This observation indicates an activation of HABR in the small fetus.

MiR-486-5p protects against rat ischemic kidney injury and prevents the transition to chronic kidney disease and vascular dysfunction.

Acute kidney injury (AKI) increases the risk for progressive chronic kidney disease (CKD). MicroRNA (miR)-486-5p protects against kidney ischemia reperfusion (IR) injury in mice, although its longterm effects on the vasculature and development of CKD are unknown. We studied whether miR-486-5p would prevent the AKI to CKD transition in rat, and affect vascular function.Methods:Adult male rats were subjected to bilateral kidney IR followed by i.v. injection of liposomal-packaged miR-486-5p (0.5 mg/kg). Kidney function and histologic injury were assessed after 24 h and 10 weeks. Kidney endothelial protein levels were measured by immunoblot and immunofluorescence, and mesenteric artery reactivity was determined by wire myography.Results:In rats with IR, miR-486-5p blocked kidney endothelial cell increases in intercellular adhesion molecule-1 (ICAM-1), reduced neutrophil infiltration and histologic injury, and normalized plasma creatinine (p<0.001). However, miR-486-5p attenuated IR-induced kidney endothelial nitric oxide synthase (eNOS) expression (p<0.05). At 10 weeks, kidneys from rats with IR alone had decreased peritubular capillary density and increased interstitial collagen deposition (p<0.0001), and mesenteric arteries showed impaired endothelium-dependent vasorelaxation (p<0.001). These changes were inhibited by miR-486-5p. Delayed miR-486-5p administration (96 h, 3 weeks after IR) had no impact on kidney fibrosis, capillary density, or endothelial function.Conclusion:In rats, administration of miR-486-5p early after kidney IR prevents injury, and protects against CKD development and systemic endothelial dysfunction. These protective effects are associated with inhibition of endothelial ICAM-1 and occur despite reduction in eNOS. miR-486-5p holds promise for the prevention of ischemic AKI and its complications.

Fetal sex and the relative reactivity of human umbilical vein and arteries are key determinants in potential beneficial effects of phosphodiesterase inhibitors.

Intrauterine growth restriction (IUGR) is a common complication of pregnancy. We previously demonstrated that IUGR is associated with an impaired nitric oxide (NO)-induced relaxation in the human umbilical vein (HUV) of growth-restricted females compared to appropriate for gestational age (AGA) newborns. We found that phosphodiesterase (PDE) inhibition improved NO-induced relaxation in HUV, suggesting that PDEs could represent promising targets for therapeutic intervention. This study aimed to investigate the effects of PDE inhibition on human umbilical arteries (HUAs) compared to HUV. Umbilical vessels were collected in IUGR and AGA term newborns. NO-induced relaxation was studied using isolated vessel tension experiments, in the presence or absence of the non-specific PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX). PDE1B, PDE1C, PDE3A, PDE4B and PDE5A were investigated by Western blot. NO-induced vasodilation was similar between IUGR and AGA HUAs. In HUAs precontracted with serotonin, IBMX enhanced NO-induced relaxation only in IUGR females, whereas in HUV IBMX increased NO-induced relaxation in all groups except IUGR males. In umbilical vessels pre-constricted with the thromboxane A2 analog U46619, IBMX improved NO-induced relaxation in all groups, in a greater extent in HUV than HUAs. However, the PDEs protein content was higher in HUAs than HUV, in all study groups. Therefore, the effects of PDE inhibition depend on the presence of IUGR, fetal sex, vessel type and vasoconstrictors implicated. Despite a higher PDEs protein content, HUAs are less sensitive to IBMX than HUV, which could lead to adverse effects of PDE inhibition in vivo, by impairment of the fetoplacental hemodynamics.

Pharmacological Targeting of Endothelial KCa Channels In Vivo Augments Vasodilatory Responses in Rat Femoral and Coronary Arteries in Health and Disease

As the primary interface between the blood and organs, the vascular endothelium functions as a key regulator of tissue blood flow by sensing chemical and mechanical stimuli and producing vasoactive signals to dynamically control intraluminal diameter in local arterioles and upstream arteries. Flow-mediated dilation (FMD) is an important physiological mechanism to modify local tissue perfusion in response to dynamic metabolic conditions, and reduced FMD responses are indicative of endothelial dysfunction, the latter being a major risk factor for cardiovascular disease. We have previously reported that pharmacological enhancement of endothelial KCa2.3 and KCa3.1 channel activity by SKA-31 augmented vasodilatory responses in small resistance arteries and intact hearts isolated from healthy and Type 2 Diabetic (T2D) rats (RC Mishra et al, 2014, 2021). In the present study, we have investigated the ability of SKA-31 to enhance endothelium-dependent vasodilation in vivo in femoral and coronary arteries of healthy and T2D male rats. Methods: FMD responses associated with reactive hyperemia were measured in a side branch of the femoral artery by high sensitivity Doppler ultrasound following release of an inflated pressure cuff placed on the distal hind limb of male Sprague Dawley (SD) and T2D Goto-Kakizaki (GK) rats (26-32 weeks of age). Rats were injected i.p. with either 10 mg/kg SKA-31 or drug vehicle ~ 3 hours prior to cuff inflation. M-mode echocardiographic imaging was used to visualize intraluminal diameter changes in the left main coronary artery in the same four treatment groups in response to an increase in inhalational isoflurane from 2% to 5%. Results: Femoral artery blood flow increased ~2-fold during reactive hyperemia in vehicle treated SD rats, as quantified by velocity-time integral, and did not increase further with SKA-31 treatment. In contrast, the FMD response in vehicle treated T2D GK rats was substantially blunted vs. SD rats, and SKA-31 administration restored this response to the level observed in healthy controls, which was still observable 15-24 hours later. In vehicle treated SD rats, exposure to 5% isoflurane increased left main coronary arterial diameter by 50-60%, which reversed to baseline following return to the original 2% isoflurane condition. SKA-31 treatment of SD rats increased basal arterial diameter by ~30%, but did not significantly modify the observed increase in arterial diameter evoked by 5% isoflurane inhalation, compared with vehicle treatment. In vehicle treated T2D GK rats, exposure to 5% isoflurane did not increase coronary artery diameter over a 10 min period, which is suggestive of endothelial dysfunction. However, SKA-31 treatment significantly increased basal coronary arterial diameter by 40-50%, and promoted a rapid and robust increase in diameter following exposure to 5% isoflurane (80-90% increase above that observed in vehicle treated T2D rats), which reversed to baseline upon return to 2% isoflurane inhalation. No enhancement of isoflurane evoked coronary vasodilation was observable in T2D GK rats 15-24 hrs post-SKA-31 treatment. In summary, these data provide the first direct demonstration that low dose administration of a KCa channel activator can enhance vasodilatory responses in vivo. This study was supported by research funding to APB from the Canadian Institutes of Health Research (MOP-142467) and NSERC (RGPIN 2017-04116). 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.

Arterial stiffness and wave reflection responses to acute and chronic high intensity interval training in healthy older adults

Aging leads to large elastic artery stiffness which is associated with early return of wave reflection. These age-related alterations increase left ventricular afterload, predisposing older adults to cardiovascular disease. Endurance training is an effective strategy to reduce cardiovascular disease risk. We have developed a supervised home-based exercise intervention using high intensity interval training on an all-extremity non-weight-bearing ergometer (HIIT-ANE). This study aimed to test the following hypotheses in healthy older adults: 1) arterial stiffness and wave reflection would decrease in response to chronic HIIT-ANE, 2) arterial stiffness and wave reflection responses to acute HIIT-ANE would differ in the untrained compared to the trained states, and 3) arterial stiffness and aortic wave reflection responses to acute and chronic HIIT-ANE would be related. Twenty older adults (66±1 years, mean ± SE; 11 postmenopausal women and 9 men) participated in this study. Carotid-femoral pulse wave velocity (cfPWV) and augmentation index at heart rate 75 bpm (AIx@75)—indices of arterial stiffness and wave reflection, respectively—were assessed by SphygmoCor XCEL at baseline (T0), following 8 weeks of normal lifestyle (T1; control condition), and following 8 weeks of supervised home-based HIIT-ANE (T2). Acute cfPWV and AIx@75 responses to HIIT-ANE were assessed at pre-, end-of-, 1-hr post- and 24-hrs post-exercise, in the untrained and trained states. cfPWV increased after 8 weeks of normal lifestyle (T0 vs. T1: 7.9±0.3 vs. 8.2±0.3 m/s, P=0.03), but it decreased following 8 weeks of HIIT-ANE (T1 vs. T2: 8.2±0.3 vs. 7.7±0.3 m/s, P&lt;0.001). AIx@75 decreased after 8 weeks of HIIT-ANE compared to baseline and following 8 weeks of normal lifestyle (T0 vs. T2: 23.7±1.8 vs. 17.8±1.9 %, P&lt;0.001; T1 vs. T2: 24.9±2.2 vs. 17.8±1.9 %, P&lt;0.001). Acute cfPWV and AIx@75 responses to HIIT-ANE were similar in the untrained and trained states ( P for condition×time interaction; cfPWV: P=0.8; AIx@75: P=0.9). cfPWV and AIx@75 responses to chronic HIIT-ANE were not significantly related with acute responses to HIIT-ANE in the untrained (cfPWV: r=0.07, P=0.8; AIx@75: r=-0.32, P=0.2) and trained states (cfPWV: r=0.10, P=0.7; AIx@75: r=-0.32, P=0.2). In conclusion, we have demonstrated that supervised home-based HIIT-ANE has beneficial vascular effects in healthy older adults. We also showed that acute vascular responses to HIIT-ANE do not change from the untrained to trained state and are not predictive of chronic vascular responses to HIIT-ANE. This work was supported by the National Institute of Aging grant AG063143. 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.

Fibulin-5 Is Required for Small Artery Development and Function

Introduction: Fibulins are a family of eight extracellular matrix proteins with diverse functions. Fibulin-4 and -5 (FBLN-4 and -5), in particular, have been shown to be important for elastic fiber assembly. Mutations in each of the genes lead to cutis laxa, a syndrome characterized by loose skin with variable organ involvement, particularly in the vasculature, lungs and skeleton. We recently characterized a mouse model carrying a disease-causing mutation in Fbln4 (E57K) and, contrary to conduit arteries that had elastic fiber fragmentation and stiffness, Fbln4E57K resistance arteries were structurally intact. Functionally however, Fbln4E57K mesenteric arteries exhibited endothelial dysfunction secondary to increased shear stress from large artery stiffness. Loss of FBLN5 has been shown to lead to elastic fiber fragmentation in conduit arteries, but the consequences of its loss on resistance arteries are unknown. Therefore, the objectives of this study were to determine the structural and functional consequences of FBLN5 loss on resistance arteries. Methods: We utilized adult Fbln5 knock-out (KO) mice and examined the ultrastructure of renal and mesenteric arteries via transmission electron microscopy. Functionally, using pressure myography, we characterized the myogenic tone and reactivity of Fbln5 KO and littermate control third-order mesenteric arteries to various vasoactive substances including acetylcholine, papaverine, angiotensin II, phenylephrine and potassium chloride. Results: While the internal elastic lamina (IEL) of Fbln5KO mice resistance arteries was largely intact, the external elastic lamina (EEL) was nearly absent. Similar to Fbln4E57K mice, Fbln5KO mesenteric arteries exhibited impaired endothelial-dependent vasorelaxation, likely secondary to proximal large artery stiffness. Unlike Fbln4E57K mesenteric arteries however, Fbln5 KO mesenteric arteries exhibited increased myogenic tone as well as a hypercontractile response to angiotensin II and potassium chloride, but not to phenylephrine. Conclusions: In addition to highlighting differences in the requirements for elastic fiber assembly along the arterial tree, these data emphasize the differential contribution of FBLN4 and FBLN5 to IEL vs. EEL in resistance arteries and suggest pathway-specific changes in smooth muscle cell contractility secondary to FBLN5 deficiency. This work was supported by the Washington University Pediatric Nephrology Research Core Pilot Grant Program to CMH. Funds were also provided by The Department of Pediatrics at Washington University in St. Louis School of Medicine to CMH. 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.

EXPLORING THE EFFECTS OF VIGOROUS INTERVAL TRAINING, MODERATE RESISTANCE TRAINING AND PILATES ON ARTERIAL STIFFNESS AND BLOOD PRESSURE DURING PREGNANCY: A RANDOMISED CROSS-OVER TRIAL

INTRODUCTION Regular moderate intensity exercise throughout pregnancy provides significant benefits to both maternal and foetal cardiovascular health outcomes. Current exercise guidelines recommend a combination of moderate intensity aerobic and resistance training (RT). However, there is limited research exploring the cardiovascular effects of higher intensities (vigorous/high) in comparison to common pregnancy exercise modalities such as RT and Pilates (PIL). AIM: To investigate the acute effects of three modes of exercise (resistance, vigorous aerobic intervals and Pilates) during trimester two (T2) and three (T3) of pregnancy on measures of arterial stiffness (pulse wave velocity [PWV]) and blood pressure (BP). METHODS Eleven women with uncomplicated pregnancies (age 32 ± 3 years, pre-pregnancy BMI 23.9 ± 3.5 kg/m2) completed testing in T2 (average 20 ± 1.6 weeks gestation) and T3 (average 29 ± 2.5 weeks gestation). Participants performed one each of vigorous intensity interval training (VIIT) (∼33 min), resistance training (RT) (∼35 min) and Pilates (PIL) (∼35 min) in T2 and T3 in randomised order approximately 1 week apart each trimester. Resting outcome measures of PWV, BP and foetal heart rate (FHR) were obtained following 5 minutes of rest and again immediately and 10 minutes post exercise session. BP, maternal heart rate (MHR), and rating of perceived exertion (RPE) were monitored throughout. RESULTS There was no difference in the acute PWV response to each type of exercise across the trimesters (1 min VIIT: T2 = 5.53 ± 0.85m/s, T3 = 5.26 ± 0.67m/s, 95%CI[-1.36-0.67]; RT: T2 = 5.4 ± 0.80m/s, T3 = 5.48 ± 0.56m/s, 95%CI[-0.88-1.10]; PIL: T2 = 5.44 ± 0.68m/s, T3 = 5.44 ± 0.68m/s, 95%CI[-0.93-1.01]). There was no significant difference in the acute response in SBP to VIIT (T2 = 116 ± 12.1mmHg, T3 = 122 ± 7.2mmHg, 95%CI[-0.42 - 1.65]. SBP was significantly higher in T3 than T2 1 minute following PIL (T2 = 110 ± 5.8mmHg, T3 = 121 ± 11.7mmHg, 95%CI[0.04-2.1]) and 10 minutes following RT (T2 = 105 ± 10.1mmHg, T3 = 116 ± 5.0mmHg, 95%CI[0.27 - 2.46]. CONCLUSION VIIT, RT and PIL appear to elicit similar post-exercise haemodynamic and arterial stiffness responses in both the mother and foetus. As such, VIIT may be a suitable addition to standard moderate intensity and RT prescription during an uncomplicated pregnancy.

Re-evaluating the Need for Routine Maximal Aerobic Capacity Testing within Fighter Pilots.

INTRODUCTION: There is a current belief in aviation suggesting that aerobic training may reduce G-tolerance due to potential negative impacts on arterial pressure response. Studies indicate that increasing maximal aerobic capacity (<mml:math id="ie1" display="inline"><mml:mrow><mml:mover><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math>o₂ max) through aerobic training does not hinder G-tolerance. Moreover, sustained centrifuge training programs revealed no instances where excessive aerobic exercise compromised a trainee's ability to complete target profiles. The purpose of this review article is to examine the current research in the hope of establishing the need for routine <mml:math id="ie2" display="inline"><mml:mrow><mml:mover><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math>o₂-max testing in air force pilot protocols.METHODS: A systematic search of electronic databases including Google Scholar, PubMed, the Aerospace Medical Association, and Military Medicine was conducted. Keywords related to "human performance," "Air Force fighter pilots," "aerobic function," and "maximal aerobic capacity" were used in various combinations. Articles addressing exercise physiology, G-tolerance, physical training, and fighter pilot maneuvers related to human performance were considered. No primary data collection involving human subjects was conducted; therefore, ethical approval was not required.RESULTS: The <mml:math id="ie3" display="inline"><mml:mrow><mml:mover><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math>o₂-max test provides essential information regarding a pilot's ability to handle increased Gz-load. It assists in predicting G-induced loss of consciousness by assessing anti-G straining maneuver performance and heart rate variables during increased G-load.DISCUSSION: <mml:math id="ie4" display="inline"><mml:mrow><mml:mover><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math>o₂-max testing guides tailored exercise plans, optimizes cardiovascular health, and disproves the notion that aerobic training hampers G-tolerance. Its inclusion in air force protocols could boost readiness, reduce health risks, and refine training for fighter pilots' safety and performance. This evidence-backed approach supports integrating <mml:math id="ie5" display="inline"><mml:mrow><mml:mover><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math>o₂-max testing for insights into fitness, risks, and tailored exercise.Zeigler Z, Acevedo AM. Re-evaluating the need for routine maximal aerobic capacity testing within fighter pilots. Aerosp Med Hum Perform. 2024; 95(5):273-277.

Cross-sexual Effects of Testosterone on Mesenteric Arterial Reactivity in Ovariectomized Female Rats

The number of transgender individuals is on the rise in the United States. Although there are studies on the effects of sex hormones on cardiovascular function of cisgender male and female, still much is not known about the effects of cross-sex hormone therapy (CSHT) on cardiovascular function in transgender individuals. It has been shown that the risk factors of cardiovascular diseases (CVD) are increased in transgenders after they undergo CSHT. Epidemiological studies suggest that transgender females (male to female, MtF) on estrogen therapy develop higher risk of CVD compared to transgender males (female to male, FtM) taking testosterone. This study investigates the effects of testosterone or estrogen treatment on the third branch of mesenteric arterial reactivity in ovariectomized female rats. Briefly, 8-10 weeks old female Sprague Dawley (SD) rats were ovariectomized (OVX) and subcutaneously implanted with placebo (OVX + PL) or testosterone (OVX + T, 7.5 mg) or 17β- estradiol (OVX + E2, 1.5 mg) pellets for about 35 days. Age matched intact female SD rats were also included in the experimental groups. Endothelium-dependent vasorelaxation (EDV) to acetylcholine (ACh) was measured in the precontracted mesenteric arteries with phenylephrine (PE), using wire myography. Responses to sodium nitroprusside (SNP)-induced vasorelaxation, and PE- and endothelin-1 (ET-1) induced vasocontraction were also determined. We demonstrated that the responses to ACh in rat mesenteric arteries were not altered by either ovariectomy or estrogen treatment. However, testosterone treatment of OVX female rats significantly enhanced the sensitivity to ACh-induced vasorelaxation compared with those in other experimental groups. Moreover, the mesenteric arteries of OVX + T exhibited a trend of reduced sensitivity to PE responses compared to other groups. Furthermore, the maximum tension to ET-1 was significantly reduced in mesenteric arteries of OVX + T compared to OVX+E2 and OVX+PL groups. The vasorelaxation responses to SNP were not altered in any of experimental groups studied. These data suggest that elevated sensitivity to ACh in testosterone-treated ovariectomized female rats might be, in part, due to reduced vessel responses to contractile agents, but not altered sensitivity of smooth muscle to nitric oxide (NO) in this group. Additional studies are needed to investigate the underlying mechanisms and document the consequences for the improvement of EDV observed in OVX + T rats. NIDA/NIGMS, 1SC1DA052120-01 to MF, Bridge Grant from University of the Pacific to RR. 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.

Does Chronotype Influence Diurnal Changes in Cardiovascular Disease Risk Factors? A Preliminary Analysis

Introduction: Humans experience diurnal fluctuations in the prevalence of cardiovascular events which is likely an output of endogenous circadian influence. Relatedly, vascular endothelial cell function, measured by conduit artery responsiveness to hyperemia during a flow-mediated dilation test, is supposed to follow a diurnal rhythm that is moderated by an individual’s chronotype. We therefore sought to examine the extent to which diurnal changes in other cardiovascular risk factors, such as blood pressure, cardiac chronotropy, and circulating blood leukocytes, were related to chronotype in humans. A moderating influence of chronotype on diurnal changes in the aforementioned parameters was hypothesized given prior research associating a preference for evening wakefulness with an adverse cardiometabolic phenotype. Methods: All data are presented as mean ± standard deviation. This abstract includes secondary data from a preliminary sample of 16 young (19 ± 2 years), healthy males and females. Participants completed a Munich Chronotype Questionnaire (MCQ) to quantify diurnal preference for morning or evening activity. The corrected mid-sleep time on free days (MSFSC) was calculated from the MCQ and interpreted to represent an index for morning or evening chronotype. Participants attended data collection sessions in the morning (09:16 ± 01:27 hh:mm) and again in the evening (16:19 ± 00:31 hh:mm) under resting conditions for the quantification of blood pressure and enumeration of circulating leukocytes from venous blood. Results: The sample included in this analysis had a slight preference for evening wakefulness (MSFSC = 04:58 ± 01:17 hh:mm). A significant and robust diurnal variation was found among circulating venous leukocytes (P &lt; 0.001) which measured higher in the afternoon (2.06×106 ± 3.67×105 cells/mL blood) than morning (1.61×106 ± 4.68×105 cells/mL blood). The diurnal variation in circulating venous leukocytes was independent (β = -9.87×104; R2 = 0.19; P = 0.186) of individual chronotype, as were individual diurnal changes of all other hemodynamic parameters included in this analysis (all P &gt; 0.05). More participants will be recruited to satisfy statistical power for primary outcomes. Discussion: These preliminary results from healthy, young adults indicate that individual disposition towards morning or evening wakefulness may not exert a profound influence over diurnal changes in several cardiovascular disease risk factors under resting conditions. Funding Sources: The study was funded by the Natural Sciences and Engineering Research Council of Canada (DG: 20011033) held by Dr. MJM). JMC and MIB were supported by Ontario Graduate Scholarships. JCS was supported by the Natural Sciences and Engineering Research Council of Canada Graduate Scholarships – Master’s. 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 nature of chronic rejection after lung transplantation: a murine orthotopic lung transplant study.

Chronic rejection is a major complication post-transplantation. Within lung transplantation, chronic rejection was considered as airway centred. Chronic Lung Allograft Dysfunction (CLAD), defined to cover all late chronic complications, makes it more difficult to understand chronic rejection from an immunological perspective. This study investigated the true nature, timing and location of chronic rejection as a whole, within mouse lung transplantation. 40 mice underwent an orthotopic left lung transplantation, were sacrificed at day 70 and evaluated by histology and in vivo µCT. For timing and location of rejection, extra grafts were sacrificed at day 7, 35, 56 and investigated by ex vivo µCT or single cell RNA (scRNA) profiling. Chronic rejection originated as innate inflammation around small arteries evolving toward adaptive organization with subsequent end-arterial fibrosis and obliterans. Subsequently, venous and pleural infiltration appeared, followed by airway related bronchiolar folding and rarely bronchiolitis obliterans was observed. Ex vivo µCT and scRNA profiling validated the time, location and sequence of events with endothelial destruction and activation as primary onset. Against the current belief, chronic rejection in lung transplantation may start as an arterial response, followed by responses in venules, pleura, and, only in the late stage, bronchioles, as may be seen in some but not all patients with CLAD.

Numerical Analysis of Mice Carotid Arteries’ Response Emphasizing the Importance of Material Law Constants’ Validation

In this paper, a detailed validation of the passive material properties of mice carotid arteries and constants of the Fung and Holzapfel hyperelastic material laws is conducted by means of static nonlinear FEM analyses. The response of the carotid arteries in an inflation test is studied here for the following mouse models: wild-type, mdx, sgcd−/−, Eln+/+, Eln+/−, Fbln5+/+, and Fbln5−/−. All FEM computations are conducted on models that have been preliminarily checked for their reliability. The results of the calculations, namely, the relation between the internal pressure and the artery outer diameter, are verified against experimental responses and the applicability of the laws is assessed. New sets of Holzapfel constitutive relation constants are proposed for Eln+/+ and Fbln5−/− mice. Finally, the problem of carotid artery buckling is also discussed. The buckling pressures of the arteries are predicted using FEM models and nonlinear static analyses. These values are compared with the reference experimental results, which allow for further validation of the constitutive relations. The research emphasizes that computations and numerical methods enable an accurate description of bioengineering processes and behaviors but only if the models used are appropriately validated.

Managing hypertension using brewing bioactive peptides as angiotensin-converting enzyme inhibitors: Impact on vascular tone through ex vivo assays

BackgroundPeptides derived from brewer’s spent grain (BSG) and yeast (BSY) are promising natural substitutes of synthetic drugs to manage hypertension as inhibitors of angiotensin-converting enzyme (ACE). However, their impact on the vascular function, so far, remains to be verified. Accordingly, we aimed to evaluate the effect of brewing peptides on the arterial vasocontractile response to angiotensin (Ang) I (through vascular ACE-inhibition) to estimate their antihypertensive potential. The impact of the oral route (gastrointestinal digestion, intestinal absorption, and liver metabolism) in brewing peptides was also investigated. MethodsIliac arteries from adult spontaneously hypertensive rats were studied with isometric tension recording. After ensuring the function integrity of the arteries, concentration-response curves to addition of Ang I (10−9-10−6 M) were performed after 30 min incubation with MIX (50:50 mixture of BSG:BSY) or BSG (0.86 mg/mL), or captopril (an ACE-inhibitory drug) or Krebs solution. ResultsMIX peptides (without simulated oral administration) enhanced Ang I-induced vasoconstriction, but lacked vascular effects after simulated oral administration. By contrast, BSG peptides (without simulated oral administration) did not exhibit vascular effects, whereas they promoted a marked decrease in vasocontraction evoked by the generated Ang II after simulation of the oral route, implying their capability to inhibit ACE. Additionally, to elucidate this inhibitory mechanism, Michaelis-Menten and Lineweaver-Burk plots indicated a mixed inhibition type. ConclusionWith simulation of the oral route, BSG peptides were able to inhibit vascular ACE with a similar efficacy as the antihypertensive drug captopril, suggesting the potential to mitigate the burden of hypertension.

Exposure to DEP Modifies the Human Umbilical Artery Vascular Resistance Contributing to Hypertension in Pregnancy.

Hypertensive disorders in pregnancy (HDP) are the most prevalent diseases during pregnancy. In addition to the already identified risk factors, exposure to environmental contaminants has been also considered a new one. Phthalates, which are classified as priority environmental pollutants due to their ubiquitousness and endocrine disrupting properties, have been implicated in HDP in some epidemiological studies. Nevertheless, phthalates' vascular impacts still need to be clarified. Thus, we aimed to understand the connection between phthalates exposure and the occurrence of gestational hypertension, as well as the pathway involved in the pathological vascular effects. We investigated diethyl phthalate's (DEP) effect on the vascular reactivity of the human umbilical arteries (HUAs) from normotensive and hypertensive pregnant women. Both DEP's nongenomic (within minutes effect) and genomic (24 h exposure to DEP) actions were evaluated, as well as the contribution of cyclic guanosine monophosphate and Ca2+ channel pathways. The results show that short-term exposure to DEP interferes with serotonin and histamine receptors, while after prolonged exposure, DEP seems to share the same vasorelaxant mechanism as estrogens, through the NO/sGC/cGMP/PKG signaling pathway, and to interfere with the L-type Ca2+ channels. Thus, the vascular effect induced by DEP is similar to that observed in HUA from hypertensive pregnancies, demonstrating that the development of HDP may be a consequence of DEP exposure.

357 Effects of Dietary Nitrate Supplementation on Vascular Function in Individuals with Prediabetes

OBJECTIVES/GOALS: Impaired vascular function, a subclinical marker of cardiovascular disease, has been identified in prediabetes. Dietary nitrate supplementation has been shown to improve vascular function. However, this has not been studied in prediabetes. The purpose was to determine the effects of dietary nitrate on vascular function in prediabetes. METHODS/STUDY POPULATION: Five individuals with prediabetes (4 men, 1 woman; 55 ± 17 yr; HbA1c = 5.8 ± 0.2) participated in a double-blind, placebo-controlled, repeated measures study. Participants were randomly assigned to a 3-day nitrate supplementation (nitrate-rich beetroot juice, 12.9 mmol, 140 mL), or a placebo supplementation (nitrate-depleted beetroot juice, 0.05 mmol, 140 mL). Following supplementation, participants reported to the lab for measures of vascular function in the lower limb. Doppler ultrasonography was used to measure flow-mediated dilation (FMD) and post-occlusive reactive hyperemia (RH) of the superficial femoral artery in response to a 5-min bout of leg ischemia. RESULTS/ANTICIPATED RESULTS: FMD did not differ between the nitrate-rich (2.87 ± 2.01%) and placebo (2.24 ± 1.69%) conditions (p = 0.48; d = 0.35). Furthermore, peak RH did not differ between the nitrate-rich (1503 ± 443 ml/min) and placebo (1762 ± 414 ml/min) conditions (p = 0.36; d = 0.46). DISCUSSION/SIGNIFICANCE: These preliminary results suggest that dietary nitrate supplementation in the form of beetroot juice does not improve vascular function in individuals with prediabetes.

Extracellular glucose and dysfunctional insulin receptor signaling independently upregulate arterial smooth muscle TMEM16A expression.

Diabetes alters the function of ion channels responsible for regulating arterial smooth muscle membrane potential, resulting in vasoconstriction. Our prior research demonstrated an elevation of TMEM16A in diabetic arteries. Here, we explored the mechanisms involved in Transmembrane protein 16A (TMEM16A) gene expression. Our data indicate that a Snail-mediated repressor complex regulates arterial TMEM16A gene transcription. Snail expression was reduced in diabetic arteries while TMEM16A expression was upregulated. The TMEM16A promoter contained three canonical E-box sites. Electrophoretic mobility and super shift assays revealed that the -154 nt E-box was the binding site of the Snail repressor complex and binding of the repressor complex decreased in diabetic arteries. High glucose induced a biphasic contractile response in pressurized nondiabetic mouse hindlimb arteries incubated ex vivo. Hindlimb arteries incubated in high glucose also showed decreased phospho-protein kinase D1 and TMEM16A expression. In hindlimb arteries from nondiabetic mice, administration of a bolus dose of glucose activated protein kinase D1 signaling to induce Snail degradation. In both in vivo and ex vivo conditions, Snail expression exhibited an inverse relationship with the expression of protein kinase D1 and TMEM16A. In diabetic mouse arteries, phospho-protein kinase D1 increased while Akt2 and pGSK3β levels declined. These results indicate that in nondiabetic mice, high glucose triggers a transient deactivation of the Snail repressor complex to increase arterial TMEM16A expression independently of insulin signaling. Conversely, insulin resistance activates GSK3β signaling and enhances arterial TMEM16A channel expression. These data have uncovered the Snail-mediated regulation of arterial TMEM16A expression and its dysfunction during diabetes.NEW & NOTEWORTHY The calcium-activated chloride channel, TMEM16A, is upregulated in the diabetic vasculature to cause increased vasoconstriction. In this paper, we have uncovered that the TMEM16A gene expression is controlled by a Snail-mediated repressor complex that uncouples with both insulin-dependent and -independent pathways to allow for upregulated arterial protein expression thereby causing vasoconstriction. The paper highlights the effect of short- and long-term glucose-induced dysfunction of an ion channel expression as a causative factor in diabetic vascular disease.

Postoperative orthostatic intolerance following fast-track unicompartmental knee arthroplasty: incidence and hemodynamics—a prospective observational cohort study

BackgroundEarly postoperative mobilization is essential for early functional recovery but can be inhibited by postoperative orthostatic intolerance (OI). Postoperative OI is common after major surgery, such as total knee arthroplasty (TKA). However, limited data are available after less extensive surgery, such as unicompartmental knee arthroplasty (UKA). We, therefore, investigated the incidence of OI as well as cardiovascular and tissue oxygenation responses during early mobilization after UKA.MethodsThis prospective single-centre observational study included 32 patients undergoing primary UKA. Incidence of OI and cardiovascular and tissue oxygenation responses during mobilization were evaluated preoperatively, at 6 and 24 h after surgery. Perioperative fluid balance, bleeding, surgery duration, postoperative hemoglobin, pain during mobilization and opioid usage were recorded.ResultsDuring mobilization at 6 h after surgery, 4 (14%, 95%CI 4–33%) patients experienced OI; however, no patients terminated the mobilization procedure prematurely. Dizziness and feeling of heat were the most common symptoms. OI was associated with attenuated systolic and mean arterial blood pressure responses in the sitting position (all p < 0.05). At 24 h after surgery, 24 (75%) patients had already been discharged, including three of the four patients with early OI. Only five patients were available for measurements, two of whom experienced OI; one terminated the mobilization procedure due to intolerable symptoms. We observed no statistically significant differences in perioperative fluid balance, bleeding, surgery duration, postoperative hemoglobin, pain, or opioid usage between orthostatic intolerant and tolerant patients.ConclusionsThe incidence of orthostatic intolerance after fast-track unicompartmental knee arthroplasty is low (~ 15%) and is associated with decreased orthostatic pressure responses. Compared to the previously described orthostatic intolerance incidence of ~ 40% following total knee arthroplasty, early orthostatic intolerance is uncommon after unicompartmental knee arthroplasty, suggesting a procedure-specific component.Trial registration: Prospectively registered at ClinicalTrials.gov; registration number: NCT04195360, registration date: 13.12.2019.

Effects of three weeks base training at moderate simulated altitude with or without hypoxic residence on exercise capacity and physiological adaptations in well-trained male runners.

To test the hypothesis that 'live high-base train high-interval train low' (HiHiLo) altitude training, compared to 'live low-train high' (LoHi), yields greater benefits on performance and physiological adaptations. Sixteen young male middle-distance runners (age, 17.0 ± 1.5 y; body mass, 58.8 ± 4.9 kg; body height, 176.3 ± 4.3 cm; training years, 3-5 y; training distance per week, 30-60 km.wk-1) with a peak oxygen uptake averaging ~65 ml.min-1.kg-1 trained in a normobaric hypoxia chamber (simulated altitude of ~2,500 m, monitored by heart rate ~170 bpm; thrice weekly) for 3 weeks. During this period, the HiHiLo group (n = 8) stayed in normobaric hypoxia (at ~2,800 m; 10 h.day-1), while the LoHi group (n = 8) resided near sea level. Before and immediately after the intervention, peak oxygen uptake and exercise-induced arterial hypoxemia responses (incremental cycle test) as well as running performance and time-domain heart rate variability (5-km time trial) were assessed. Hematological variables were monitored at baseline and on days 1, 7, 14 and 21 during the intervention. Peak oxygen uptake and running performance did not differ before and after the intervention in either group (all P > 0.05). Exercise-induced arterial hypoxemia responses, measured both at submaximal (240 W) and maximal loads during the incremental test, and log-transformed root mean square of successive R-R intervals during the 4-min post-run recovery period, did not change (all P > 0.05). Hematocrit, mean reticulocyte absolute count and reticulocyte percentage increased above baseline levels on day 21 of the intervention (all P < 0.001), irrespective of group. Well-trained runners undertaking base training at moderate simulated altitude for 3 weeks, with or without hypoxic residence, showed no performance improvement, also with unchanged time-domain heart rate variability and exercise-induced arterial hypoxemia responses.

The β-catenin C terminus links Wnt and sphingosine-1-phosphate signaling pathways to promote vascular remodeling and atherosclerosis.

Canonical Wnt and sphingosine-1-phosphate (S1P) signaling pathways are highly conserved systems that contribute to normal vertebrate development, with key consequences for immune, nervous, and cardiovascular system function; despite these functional overlaps, little is known about Wnt/β-catenin-S1P cross-talk. In the vascular system, both Wnt/β-catenin and S1P signals affect vessel maturation, stability, and barrier function, but information regarding their potential coordination is scant. We report an instance of functional interaction between the two pathways, including evidence that S1P receptor 1 (S1PR1) is a transcriptional target of β-catenin. By studying vascular smooth muscle cells and arterial injury response, we find a specific requirement for the β-catenin carboxyl terminus, which acts to induce S1PR1, and show that this interaction is essential for vascular remodeling. We also report that pharmacological inhibition of the β-catenin carboxyl terminus reduces S1PR1 expression, neointima formation, and atherosclerosis. These findings provide mechanistic understanding of how Wnt/β-catenin and S1P systems collaborate during vascular remodeling and inform strategies for therapeutic manipulation.

Reactive oxygen species augment contractile responses of saphenous artery in 10-15-day-old but not adult rats: Substantial role of NADPH oxidases

Reactive oxygen species (ROS) produced by NADPH oxidases (NOX, a key source of ROS in vascular cells) are involved in the regulation of vascular tone, but this has been explored mainly for adult organisms. Importantly, the mechanisms of vascular tone regulation differ significantly in early postnatal ontogenesis and adulthood, while the vasomotor role of ROS in immature systemic arteries is poorly understood. We tested the hypothesis that the functional contribution of NADPH oxidase-derived ROS to the regulation of peripheral arterial tone is higher in the early postnatal period than in adulthood. We studied saphenous arteries from 10‐ to 15‐day‐old (“young”) and 3‐ to 4-month-old (“adult”) male rats using lucigenin-enhanced chemiluminescence, quantitative PCR, Western blotting, and isometric myography. We demonstrated that both basal and NADPH-stimulated superoxide anion radical (O2•−) production was significantly higher in the arteries from young in comparison to adult rats. Importantly, pan-inhibitor of NADPH oxidase VAS2870 (10 μM) reduced NADPH-induced O2•− production in arteries of young rats. Saphenous arteries of both young and adult rats demonstrated high levels of Nox2 and Nox4 mRNAs, while Nox1 and Nox3 mRNAs were not detected. The protein contents of NOX2 and NOX4 were significantly higher in arterial tissue of young compared to adult animals. Moreover, VAS2870 (10 μM) had no effect on methoxamine-induced contractile responses of adult arteries but decreased them significantly in young arteries; such effect of VAS2870 persisted after removal of the endothelium. Finally, NOX2 inhibitor GSK2795039 (10 μM), but not NOX1/4 inhibitor GKT137831 (10 μM) weakened methoxamine-induced contractile responses of arteries from young rats. Thus, ROS produced by NOX2 have a pronounced contractile influence in saphenous artery smooth muscle cells of young, but not adult rats, which is associated with the increased vascular content of NOX2 protein at this age.