Activating P2Y1 receptors improves function in arteries with repressed autophagy.

AIM: The importance of endothelial cell (EC) autophagy to vascular homeostasis in the context of health and disease is evolving. Earlier, we reported that intact EC autophagy is requisite to maintain shear-stress-induced nitric oxide (NO) generation via glycolysis-dependent purinergic signalling to endothelial NO synthase (eNOS). Here, we illustrate the translational and functional significance of these findings. METHODS AND RESULTS: First, we assessed translational relevance using older male humans and mice that exhibit blunted EC autophagy and impaired arterial function vs. adult controls. Active hyperaemia evoked by rhythmic handgrip exercise-elevated radial artery shear-rate similarly from baseline in adult and older subjects for 60 min. Compared with baseline, indexes of autophagy initiation, p-eNOSS1177 activation, and NO generation, occurred in radial artery ECs obtained from adult but not older volunteers. Regarding mice, indexes of autophagy and p-eNOSS1177 activation were robust in ECs from adult but not older animals that completed 60-min treadmill-running. Furthermore, 20 dyne • cm2 laminar shear stress × 45-min increased autophagic flux, glycolysis, ATP production, and p-eNOSS1177 in primary arterial ECs obtained from adult but not older mice. Concerning functional relevance, we next questioned whether the inability to initiate EC autophagy, glycolysis, and p-eNOSS1177in vitro precipitates arterial dysfunction ex vivo. Compromised intraluminal flow-mediated vasodilation displayed by arteries from older vs. adult mice was recapitulated in vessels from adult mice by (i) NO synthase inhibition; (ii) acute autophagy impairment using 3-methyladenine (3-MA); (iii) EC Atg3 depletion (iecAtg3KO mice); (iv) purinergic 2Y1-receptor (P2Y1-R) blockade; and (v) germline depletion of P2Y1-Rs. Importantly, P2Y1-R activation using 2-methylthio-ADP (2-Me-ADP) improved vasodilatory capacity in arteries from (i) adult mice treated with 3-MA; (ii) adult iecAtg3KO mice; and (iii) older animals with repressed EC autophagy. CONCLUSIONS: Arterial dysfunction concurrent with pharmacological, genetic, and age-associated EC autophagy compromise is improved by activating P2Y1-Rs.

The dynamic adjustment of mean arterial pressure during exercise: a potential tool for discerning cardiovascular health status.

The regulation of mean arterial pressure (MAP) during exercise has important physiological and clinical implications. Kinetics analysis on numerous physiological variables following the transition from unloaded-to-loaded exercise has revealed important information regarding their control. Surprisingly, the dynamic response of MAP during this transition remains to be quantified. Therefore, ten healthy participants (5/5 M/F, 24 ± 3 yr) completed repeated transitions from unloaded to moderate- and heavy-intensity dynamic single-leg knee-extensor exercise to investigate the on-kinetics of MAP. Following the transition to loaded exercise, MAP increased in a first-order dynamic manner, subsequent to a time delay (moderate: 23 ± 10; heavy: 19 ± 9 s, P > 0.05) at a speed (τ, moderate: 59 ± 30; heavy: 66 ± 19 s, P > 0.05), which did not differ between intensities, but the MAP amplitude was doubled during heavy-intensity exercise (moderate: 12 ± 5; heavy: 24 ± 8 mmHg, P < 0.001). The reproducibility [coefficient of variation (CV)] during heavy intensity for unloaded baseline, amplitude, and mean response time, when assessed as individual transitions, was 7 ± 1%, 18 ± 2%, and 25 ± 4%, respectively. Averaging two transitions improved the CVs to 4 ± 1%, 8 ± 2%, and 13 ± 3%, respectively. Preliminary findings supporting the clinical relevance of evaluating MAP kinetics in middle-aged hypertensive (n = 5) and, age-matched, normotensive (n = 5) participants revealed an exaggerated MAP response in both older groups (P < 0.05), but the MAP response was slowed only for the patients with hypertension (P < 0.05). It is concluded that kinetics modeling of MAP is practical for heavy-intensity knee-extensor exercise and may provide insight into cardiovascular health and the effect of aging.NEW & NOTEWORTHY Kinetics analysis of physiological variables following workload transitions provides important information, but this has not been performed on mean arterial pressure (MAP), despite the clear clinical importance of this variable. This investigation reveals that kinetic modeling of MAP following unloaded-to-loaded knee-extensor exercise is practical and repeatable. Additional preliminary findings in hypertensive and, age-matched, normotensive subjects suggest that MAP kinetics may provide insight into cardiovascular health and the effect of aging.

The role of endothelin A receptors in peripheral vascular control at rest and during exercise in patients with hypertension.

KEY POINTS: Exercise in patients with hypertension can be accompanied by an abnormal cardiovascular response that includes attenuated blood flow and an augmented pressor response. Endothelin-1, a very potent vasoconstrictor, is a key modulator of blood flow and pressure during in health and has been implicated as a potential cause of the dysfunction in hypertension. We assessed the role of endothelin-1, acting through endothelin A (ETA ) receptors, in modulating the central and peripheral cardiovascular responses to exercise in patients with hypertension via local antagonism of these receptors during exercise. ETA receptor antagonism markedly increased leg blood flow, vascular conductance, oxygen delivery, and oxygen consumption during exercise; interestingly, these changes occurred in the presence of reduced leg perfusion pressure, indicating that these augmentations were driven by changes in vascular resistance. These data indicate that ETA receptor antagonism could be a viable therapeutic approach to improve blood flow during exercise in hypertension. ABSTRACT: Patients with hypertension can exhibit impaired muscle blood flow and exaggerated increases in blood pressure during exercise. While endothelin (ET)-1 plays a role in regulating blood flow and pressure during exercise in health, little is known about the role of ET-1 in the cardiovascular response to exercise in hypertension. Therefore, eight volunteers diagnosed with hypertension were studied during exercise with either saline or BQ-123 (ETA receptor antagonist) infusion following a 2-week withdrawal of anti-hypertensive medications. The common femoral artery and vein were catheterized for drug infusion, blood collection and blood pressure measurements, and leg blood flow was measured by Doppler ultrasound. Patients exercised at both absolute (0, 5, 10, 15 W) and relative (40, 60, 80% peak power) intensities. BQ-123 increased blood flow at rest (79 ± 87 ml/min; P = 0.03) and augmented the exercise-induced hyperaemia at most intensities (80% saline: Δ3818±1222 vs. BQ-123: Δ4812±1469 ml/min; P = 0.001). BQ-123 reduced leg MAP at rest (-8 ± 4 mmHg; P < 0.001) and lower intensities (0-10 W; P < 0.05). Systemic diastolic blood pressure was reduced (0 W, 40%; P < 0.05), but systemic MAP was defended by an increased cardiac output. The exercise pressor response (ΔMAP) did not differ between conditions (80% saline: 25 ± 10, BQ-123: 30 ± 7 mmHg; P = 0.17). Thus, ET-1, acting through the ETA receptors, contributes to the control of blood pressure at rest and lower intensity exercise in these patients. Furthermore, the finding that ET-1 constrains the blood flow response to exercise suggests that ETA receptor antagonism could be a therapeutic approach to improve blood flow during exercise in hypertension.

Elevated arterial shear rate increases indexes of endothelial cell autophagy and nitric oxide synthase activation in humans.

Continuous laminar shear stress increases the process of autophagy, activates endothelial nitric oxide (NO) synthase phosphorylation at serine 1177 (p-eNOSS1177), and generates NO in bovine and human arterial endothelial cells (ECs) compared with static controls. However, the translational relevance of these findings has not been explored. In the current study, primary ECs were collected from the radial artery of 7 men using sterile J-wires before (Pre) and after (Post) 60 min of rhythmic handgrip exercise (HG) performed with the same arm. After ECs were identified by positive costaining for vascular endothelial cadherin and 4',6'-diamidino-2-phenylindole, immunofluorescent antibodies were used to assess indices of autophagy, NO generation, and superoxide anion (O2·-) production. Commercially available primary human arterial ECs were stained and processed in parallel to serve as controls. All end points were evaluated using 75 ECs from each subject. Relative to Pre-HG, HG elevated arterial shear rate ( P < 0.05) ~3-fold, whereas heart rate, arterial pressure, and cardiac output were not altered. Compared with values obtained from ECs Pre-HG, Post-HG ECs displayed increased ( P < 0.05) expression of p-eNOSS1177, NO generation, O2·- production, BECLIN1, microtubule-associated proteins 1A/1B light chain 3B, autophagy-related gene 3, and lysosomal-associated membrane protein 2A and decreased ( P < 0.05) expression (i.e., enhanced degradation) of the adaptor protein p62/sequestosome-1. These novel findings provide evidence that elevated arterial shear rate associated with functional hyperemia initiates autophagy, activates p-eNOSS1177, and increases NO and O2·- generation in primary human ECs. NEW & NOTEWORTHY Previously, our group reported in bovine arterial and human arterial endothelial cells (ECs) that shear stress initiates trafficking of the autophagosome to the lysosome and increases endothelial nitric oxide (NO) synthase phosphorylation at serine 1177, NO generation, and O2·- production. Here, the translational relevance of these findings is documented. Specifically, functional hyperemia induced by rhythmic handgrip exercise elevates arterial shear rate to an extent that increases indices of autophagy, NO generation, and O2·- production in primary arterial ECs collected from healthy men.