1
|
Obeid H, Bikia V, Fortier C, Paré M, Segers P, Stergiopulos N, Agharazii M. Assessment of Stiffness of Large to Small Arteries in Multistage Renal Disease Model: A Numerical Study. Front Physiol 2022; 13:832858. [PMID: 35432001 PMCID: PMC9005905 DOI: 10.3389/fphys.2022.832858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 02/23/2022] [Indexed: 01/01/2023] Open
Abstract
Arterial stiffness (AS), as assessed via pulse wave velocity (PWV), is a major biomarker for cardiovascular risk assessment in patients with chronic kidney disease (CKD). However, the mechanisms responsible for the changes in PWV in the presence of kidney disease are not yet fully elucidated. In the present study, we aimed to investigate the direct effects attributable to biomechanical changes in the arterial tree caused by staged renal removal, independent of any biochemical or compensatory effects. Particularly, we simulated arterial pressure and flow using a previously validated one-dimensional (1-D) model of the cardiovascular system with different kidney configurations: two kidneys (2KDN), one single kidney (1KDN), no kidneys (0KDN), and a transplanted kidney (TX) attached to the external iliac artery. We evaluated the respective variations in blood pressure (BP), as well as AS of large-, medium-, and small-sized arteries via carotid-femoral PWV (cfPWV), carotid-radial PWV (crPWV), and radial-digital PWV (rdPWV), respectively. Our results showed that BP was increased in 1KDN and 0KDN, and that systolic BP values were restored in the TX configuration. Furthermore, a rise was reported in all PWVs for all tested configurations. The relative difference in stiffness from 2KDN to 0KDN was higher in the case of crPWV (15%) in comparison with the increase observed for cfPWV (11%). In TX, we observed a restoration of the PWVs to values close to 1KDN. Globally, it was demonstrated that alterations of the outflow boundaries to the renal arteries with staged kidney removal led to changes in BP and central and peripheral PWV in line with previously reported clinical data. Our findings suggest that the PWV variations observed in clinical practice with different stages of kidney disease may be partially attributed to biomechanical alterations of the arterial tree and their effect on BP.
Collapse
Affiliation(s)
- Hasan Obeid
- CHU de Québec Research Center, L’Hôtel-Dieu de Québec Hospital, Québec City, QC, Canada
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Université Laval, Québec City, QC, Canada
| | - Vasiliki Bikia
- Laboratory of Hemodynamics and Cardiovascular Technology, Swiss Federal Institute of Technology Lausanne, Lausanne, Switzerland
| | - Catherine Fortier
- CHU de Québec Research Center, L’Hôtel-Dieu de Québec Hospital, Québec City, QC, Canada
- Department of Médicine, Research Centre of the Hôpital du Sacré-Coeur de Montréal, Université de Montréal, Montréal, QC, Canada
| | - Mathilde Paré
- CHU de Québec Research Center, L’Hôtel-Dieu de Québec Hospital, Québec City, QC, Canada
| | - Patrick Segers
- BioMMeda – Institute for Biomedical Engineering and Technology, Ghent University, Ghent, Belgium
| | - Nikos Stergiopulos
- Laboratory of Hemodynamics and Cardiovascular Technology, Swiss Federal Institute of Technology Lausanne, Lausanne, Switzerland
| | - Mohsen Agharazii
- CHU de Québec Research Center, L’Hôtel-Dieu de Québec Hospital, Québec City, QC, Canada
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Université Laval, Québec City, QC, Canada
- *Correspondence: Mohsen Agharazii,
| |
Collapse
|
2
|
Stone RM, Ainslie PN, Tremblay JC, Akins JD, MacLeod DB, Tymko MM, DeSouza CA, Bain AR. GLOBAL REACH 2018: intra-arterial vitamin C improves endothelial-dependent vasodilatory function in humans at high altitude. J Physiol 2021; 600:1373-1383. [PMID: 34743333 DOI: 10.1113/jp282281] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 10/11/2021] [Indexed: 12/20/2022] Open
Abstract
High altitude-induced hypoxaemia is often associated with peripheral vascular dysfunction. However, the basic mechanism(s) underlying high-altitude vascular impairments remains unclear. This study tested the hypothesis that oxidative stress contributes to the impairments in endothelial function during early acclimatization to high altitude. Ten young healthy lowlanders were tested at sea level (344 m) and following 4-6 days at high altitude (4300 m). Vascular endothelial function was determined using the isolated perfused forearm technique with forearm blood flow (FBF) measured by strain-gauge venous occlusion plethysmography. FBF was quantified in response to acetylcholine (ACh), sodium nitroprusside (SNP) and a co-infusion of ACh with the antioxidant vitamin C (ACh+VitC). The total FBF response to ACh (area under the curve) was ∼30% lower at high altitude than at sea level (P = 0.048). There was no difference in the response to SNP at high altitude (P = 0.860). At sea level, the co-infusion of ACh+VitC had no influence on the FBF dose response (P = 0.268); however, at high altitude ACh+VitC resulted in an average increase in the FBF dose response by ∼20% (P = 0.019). At high altitude, the decreased FBF response to ACh, and the increase in FBF in response to ACh+VitC, were associated with the magnitude of arterial hypoxaemia (R2 = 0.60, P = 0.008 and R2 = 0.63, P = 0.006, respectively). Collectively, these data support the hypothesis that impairments in vascular endothelial function at high altitude are in part attributable to oxidative stress, a consequence of the magnitude of hypoxaemia. These data extend our basic understanding of vascular (mal)adaptation to high-altitude sojourns, with important implications for understanding the aetiology of high altitude-related vascular dysfunction. KEY POINTS: Vascular dysfunction has been demonstrated in lowlanders at high altitude (>4000 m). However, the extent of impairment and the delineation of contributing mechanisms have remained unclear. Using the gold-standard isolated perfused forearm model, we determined the extent of vasodilatory dysfunction and oxidative stress as a contributing mechanism in healthy lowlanders before and 4-6 days after rapid ascent to 4300 m. The total forearm blood flow response to acetylcholine at high altitude was decreased by ∼30%. Co-infusion of acetylcholine with the antioxidant vitamin C partially restored the total forearm blood flow by ∼20%. The magnitude of forearm blood flow reduction, as well as the impact of oxidative stress, was positively associated with the individual severity of hypoxaemia. These data extend our basic understanding of vascular (mal)adaptation to high-altitude sojourns, with important implications for understanding the aetiology of high altitude-related changes in endothelial-mediated vasodilatory function.
Collapse
Affiliation(s)
- Rachel M Stone
- Faculty of Human Kinetics, University of Windsor, Ontario, Canada
| | - Philip N Ainslie
- Kelowna, Centre for Heart Lung and Vascular Health, University of British Columbia, Vancouver, Canada
| | - Joshua C Tremblay
- Kelowna, Centre for Heart Lung and Vascular Health, University of British Columbia, Vancouver, Canada
| | | | - David B MacLeod
- Duke University School of Medicine, Durham, North Carolina, USA
| | | | | | - Anthony R Bain
- Faculty of Human Kinetics, University of Windsor, Ontario, Canada
| |
Collapse
|
3
|
Tremblay JC, Ainslie PN, Turner R, Gatterer H, Schlittler M, Woyke S, Regli IB, Strapazzon G, Rauch S, Siebenmann C. Endothelial function and shear stress in hypobaric hypoxia: time course and impact of plasma volume expansion in men. Am J Physiol Heart Circ Physiol 2020; 319:H980-H994. [PMID: 32886005 DOI: 10.1152/ajpheart.00597.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
High-altitude exposure typically reduces endothelial function, and this is modulated by hemoconcentration resulting from plasma volume contraction. However, the specific impact of hypobaric hypoxia independent of external factors (e.g., cold, varying altitudes, exercise, diet, and dehydration) on endothelial function is unknown. We examined the temporal changes in blood viscosity, shear stress, and endothelial function and the impact of plasma volume expansion (PVX) during exposure to hypobaric hypoxia while controlling for external factors. Eleven healthy men (25 ± 4 yr, mean ± SD) completed two 4-day chamber visits [normoxia (NX) and hypobaric hypoxia (HH; equivalent altitude, 3,500 m)] in a crossover design. Endothelial function was assessed via flow-mediated dilation in response to transient (reactive hyperemia; RH-FMD) and sustained (progressive handgrip exercise; SS-FMD) increases in shear stress before entering and after 1, 6, 12, 48, and 96 h in the chamber. During HH, endothelial function was also measured on the last day after PVX to preexposure levels (1,140 ± 320 mL balanced crystalloid solution). Blood viscosity and arterial shear stress increased on the first day during HH compared with NX and remained elevated at 48 and 96 h (P < 0.005). RH-FMD did not differ during HH compared with NX and was unaffected by PVX despite reductions in blood viscosity (P < 0.05). The stimulus-response slope of increases in shear stress to vasodilation during SS-FMD was preserved in HH and increased by 44 ± 73% following PVX (P = 0.023). These findings suggest that endothelial function is maintained in HH when other stressors are absent and that PVX improves endothelial function in a shear-stress stimulus-specific manner.NEW & NOTEWORTHY Using a normoxic crossover study design, we examined the impact of hypobaric hypoxia (4 days; altitude equivalent, 3,500 m) and hemoconcentration on blood viscosity, shear stress, and endothelial function. Blood viscosity increased during the hypoxic exposure and was accompanied by elevated resting and exercising arterial shear stress. Flow-mediated dilation stimulated by reactive hyperemia and handgrip exercise was preserved throughout the hypoxic exposure. Plasma volume expansion reversed the hypoxia-associated hemoconcentration and selectively increased handgrip exercise flow-mediated dilation.
Collapse
Affiliation(s)
- Joshua C Tremblay
- Centre for Heart, Lung and Vascular Health, University of British Columbia-Okanagan, Kelowna, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia-Okanagan, Kelowna, Canada
| | - Rachel Turner
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Maja Schlittler
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Simon Woyke
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Ivo B Regli
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesia and Intensive Care Medicine, "F. Tappeiner" Hospital, Merano, Italy
| | - Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Simon Rauch
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesia and Intensive Care Medicine, "F. Tappeiner" Hospital, Merano, Italy
| | | |
Collapse
|
4
|
Tymko MM, Lawley JS, Ainslie PN, Hansen AB, Hofstaetter F, Rainer S, Amin S, Moralez G, Gasho C, Vizcardo-Galindo G, Bermudez D, Villafuerte FC, Hearon CM. Global Reach 2018 Heightened α-Adrenergic Signaling Impairs Endothelial Function During Chronic Exposure to Hypobaric Hypoxia. Circ Res 2020; 127:e1-e13. [PMID: 32268833 DOI: 10.1161/circresaha.119.316053] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
RATIONALE Chronic exposure to hypoxia is associated with elevated sympathetic nervous activity and reduced vascular function in lowlanders, and Andean highlanders suffering from excessive erythrocytosis (EE); however, the mechanistic link between chronically elevated sympathetic nervous activity and hypoxia-induced vascular dysfunction has not been determined. OBJECTIVE To determine the impact of heightened sympathetic nervous activity on resistance artery endothelial-dependent dilation (EDD), and endothelial-independent dilation, in lowlanders and Andean highlanders with and without EE. METHODS AND RESULTS We tested healthy lowlanders (n=9) at sea level (344 m) and following 14 to 21 days at high altitude (4300 m), and permanent Andean highlanders with (n=6) and without (n=9) EE at high altitude. Vascular function was assessed using intraarterial infusions (3 progressive doses) of acetylcholine (ACh; EDD) and sodium nitroprusside (endothelial-independent dilation) before and after local α+β adrenergic receptor blockade (phentolamine and propranolol). Intraarterial blood pressure, heart rate, and simultaneous brachial artery diameter and blood velocity were recorded at rest and during drug infusion. Changes in forearm vascular conductance were calculated. The main findings were (1) chronic hypoxia reduced EDD in lowlanders (changes in forearm vascular conductance from sea level: ACh1: -52.7±19.6%, ACh2: -25.4±38.7%, ACh3: -35.1±34.7%, all P≤0.02); and in Andeans with EE compared with non-EE (changes in forearm vascular conductance at ACh3: -36.4%, P=0.007). Adrenergic blockade fully restored EDD in lowlanders at high altitude, and normalized EDD between EE and non-EE Andeans. (2) Chronic hypoxia had no effect on endothelial-independent dilation in lowlanders, and no differences were detected between EE and non-EE Andeans; however, EID was increased in the non-EE Andeans after adrenergic blockade (P=0.012), but this effect was not observed in the EE Andeans. CONCLUSIONS These data indicate that chronic hypoxia reduces EDD via heightened α-adrenergic signaling in lowlanders and in Andeans with EE. These vascular mechanisms have important implications for understanding the physiological consequences of acute and chronic high altitude adaptation.
Collapse
Affiliation(s)
- Michael M Tymko
- From the Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada (M.M.T., P.N.A.).,Neurovascular Health Lab, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Canada (M.M.T.)
| | - Justin S Lawley
- University of Innsbruck, Austria (J.S.L., A.B.H., F.H., S.R., S.A.)
| | - Philip N Ainslie
- From the Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada (M.M.T., P.N.A.)
| | | | | | - Simon Rainer
- University of Innsbruck, Austria (J.S.L., A.B.H., F.H., S.R., S.A.)
| | - Sachin Amin
- University of Innsbruck, Austria (J.S.L., A.B.H., F.H., S.R., S.A.)
| | - Gilbert Moralez
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX (G.M.)
| | | | | | | | | | - Christopher M Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas (C.M.H.).,Department of Internal Medicine, University of Texas Southwestern Medical Center (C.M.H.)
| |
Collapse
|
5
|
Tymko MM, Tremblay JC, Bailey DM, Green DJ, Ainslie PN. The impact of hypoxaemia on vascular function in lowlanders and high altitude indigenous populations. J Physiol 2019; 597:5759-5776. [PMID: 31677355 DOI: 10.1113/jp277191] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 10/07/2019] [Indexed: 12/18/2022] Open
Abstract
Exposure to hypoxia elicits widespread physiological responses that are critical for successful acclimatization; however, these responses may induce apparent maladaptive consequences. For example, recent studies conducted in both the laboratory and the field (e.g. at high altitude) have demonstrated that endothelial function is reduced in hypoxia. Herein, we review the several proposed mechanism(s) pertaining to the observed reduction in endothelial function in hypoxia including: (i) changes in blood flow patterns (i.e. shear stress), (ii) increased inflammation and production of reactive oxygen species (i.e. oxidative stress), (iii) heightened sympathetic nerve activity, and (iv) increased red blood cell concentration and mass leading to elevated nitric oxide scavenging. Although some of these mechanism(s) have been examined in lowlanders, less in known about endothelial function in indigenous populations that have chronically adapted to environmental hypoxia for millennia (e.g. the Peruvian, Tibetan and Ethiopian highlanders). There is some evidence indicating that healthy Tibetan and Peruvian (i.e. Andean) highlanders have preserved endothelial function at high altitude, but less is known about the Ethiopian highlanders. However, Andean highlanders suffering from chronic mountain sickness, which is characterized by an excessive production of red blood cells, have markedly reduced endothelial function. This review will provide a framework and mechanistic model for vascular endothelial adaptation to hypoxia in lowlanders and highlanders. Elucidating the pathways responsible for vascular adaption/maladaptation to hypoxia has potential clinical implications for disease featuring low oxygen delivery (e.g. heart failure, pulmonary disease). In addition, a greater understanding of vascular function at high altitude will clinically benefit the global estimated 85 million high altitude residents.
Collapse
Affiliation(s)
- Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.,Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Joshua C Tremblay
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, UK
| | - Daniel J Green
- Cardiovascular Research Group, School of Human Sciences (Exercise and Sport Science), University of Western Australia, Perth, Australia.,Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| |
Collapse
|
6
|
Holmström P, Mulder E, Sundström AL, Limbu P, Schagatay E. The Magnitude of Diving Bradycardia During Apnea at Low-Altitude Reveals Tolerance to High Altitude Hypoxia. Front Physiol 2019; 10:1075. [PMID: 31507443 PMCID: PMC6714063 DOI: 10.3389/fphys.2019.01075] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/05/2019] [Indexed: 11/13/2022] Open
Abstract
Acute mountain sickness (AMS) is a potentially life-threatening illness that may develop during exposure to hypoxia at high altitude (HA). Susceptibility to AMS is highly individual, and the ability to predict it is limited. Apneic diving also induces hypoxia, and we aimed to investigate whether protective physiological responses, i.e., the cardiovascular diving response and spleen contraction, induced during apnea at low-altitude could predict individual susceptibility to AMS. Eighteen participants (eight females) performed three static apneas in air, the first at a fixed limit of 60 s (A1) and two of maximal duration (A2-A3), spaced by 2 min, while SaO2, heart rate (HR) and spleen volume were measured continuously. Tests were conducted in Kathmandu (1470 m) before a 14 day trek to mount Everest Base Camp (5360 m). During the trek, participants reported AMS symptoms daily using the Lake Louise Questionnaire (LLQ). The apnea-induced HR-reduction (diving bradycardia) was negatively correlated with the accumulated LLQ score in A1 (r s = -0.628, p = 0.005) and A3 (r s = -0.488, p = 0.040) and positively correlated with SaO2 at 4410 m (A1: r = 0.655, p = 0.003; A2: r = 0.471, p = 0.049; A3: r = 0.635, p = 0.005). Baseline spleen volume correlated negatively with LLQ score (r s = -0.479, p = 0.044), but no correlation was found between apnea-induced spleen volume reduction with LLQ score (r s = 0.350, p = 0.155). The association between the diving bradycardia and spleen size with AMS symptoms suggests links between physiological responses to HA and apnea. Measuring individual responses to apnea at sea-level could provide means to predict AMS susceptibility prior to ascent.
Collapse
Affiliation(s)
- Pontus Holmström
- Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden
| | - Eric Mulder
- Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden
| | | | - Prakash Limbu
- Department of Clinical Physiology, Nepalese Army Institute of Health Sciences, Kathmandu, Nepal
| | - Erika Schagatay
- Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden
| |
Collapse
|
7
|
Peciuliene I, Vilys L, Jakubauskiene E, Zaliauskiene L, Kanopka A. Hypoxia alters splicing of the cancer associated Fas gene. Exp Cell Res 2019; 380:29-35. [PMID: 31002816 DOI: 10.1016/j.yexcr.2019.04.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/08/2019] [Accepted: 04/14/2019] [Indexed: 02/02/2023]
Abstract
The removal of introns from mRNA precursors (pre-mRNAs) is an essential step in eukaryotic gene expression. The splicing machinery heavily contributes to biological complexity and especially to the ability of cells to adapt to altered cellular conditions. Hypoxia also plays a key role in the pathophysiology of many disease states. Recent studies have revealed that tumorigenesis and hypoxia involve large-scale alterations in alternative pre-mRNA splicing. Cancer associated Fas protein plays a central role in the physiological regulation of programmed cell death and has been implicated in the pathogenesis of various malignancies and diseases of the immune system. Fas pre-mRNA is alternatively spliced by excluding exon 6 to produce soluble Fas (sFas) protein that lacks a transmembrane domain and acts by inhibiting Fas mediated apoptosis. Another cancer related protein Rac1 plays an important regulatory role specifically in cells' motility, growth and survival. Rac pre-mRNA is alternatively spliced to produce Rac1b protein, which is upregulated in metastatic diseases. In the present study we, for the first time, show that anti-apoptotic Fas mRNA isoform formation is regulated by cellular microenvironment - hypoxia. Hypoxic microenvironment, however, does not influence Rac1 pre-mRNAs alternative splicing. Also our presented results indicate that splicing factors hnRNP A1 and SPF45, previously shown to regulate Fas alternative splicing in normoxic cells, are not involved in hypoxia dependent alternative Fas pre-mRNA splicing regulation in an amount dependent manner. Our observations on hypoxia dependent alternative Fas pre-mRNA splicing regulation indicate a probable involvement of other, yet unidentified splicing factors. Presented data also shows the contribution of pre-mRNA splicing to cell survival under unfavorable conditions.
Collapse
Affiliation(s)
- Inga Peciuliene
- Department of Immunology and Cell Biology, Vilnius University, Institute of Biotechnology, Vilnius, Lithuania
| | - Laurynas Vilys
- Department of Immunology and Cell Biology, Vilnius University, Institute of Biotechnology, Vilnius, Lithuania
| | - Egle Jakubauskiene
- Department of Immunology and Cell Biology, Vilnius University, Institute of Biotechnology, Vilnius, Lithuania
| | | | - Arvydas Kanopka
- Department of Immunology and Cell Biology, Vilnius University, Institute of Biotechnology, Vilnius, Lithuania.
| |
Collapse
|
8
|
Simpson LL, Busch SA, Oliver SJ, Ainslie PN, Stembridge M, Steinback CD, Moore JP. Baroreflex control of sympathetic vasomotor activity and resting arterial pressure at high altitude: insight from Lowlanders and Sherpa. J Physiol 2019; 597:2379-2390. [PMID: 30893472 DOI: 10.1113/jp277663] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/18/2019] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS Hypoxia, a potent activator of the sympathetic nervous system, is known to increase muscle sympathetic nerve activity (MSNA) to the peripheral vasculature of native Lowlanders during sustained high altitude (HA) exposure. We show that the arterial baroreflex control of MSNA functions normally in healthy Lowlanders at HA, and that upward baroreflex resetting permits chronic activation of basal sympathetic vasomotor activity under this condition. The baroreflex MSNA operating point and resting sympathetic vasomotor outflow both are lower for highland Sherpa compared to acclimatizing Lowlanders; these lower levels may represent beneficial hypoxic adaptation in Sherpa. Acute hyperoxia at HA had minimal effect on baroreflex control of MSNA in Lowlanders and Sherpa, raising the possibility that mechanisms other than peripheral chemoreflex activation contribute to vascular sympathetic baroreflex resetting and sympathoexcitation. These findings provide a better understanding of sympathetic nervous system activation and the control of blood pressure during the physiological stress of sustained HA hypoxia. ABSTRACT Exposure to high altitude (HA) is characterized by heightened muscle sympathetic neural activity (MSNA); however, the effect on arterial baroreflex control of MSNA is unknown. Furthermore, arterial baroreflex control at HA may be influenced by genotypic and phenotypic differences between lowland and highland natives. Fourteen Lowlanders (12 male) and nine male Sherpa underwent haemodynamic and sympathetic neural assessment at low altitude (Lowlanders, low altitude; 344 m, Sherpa, Kathmandu; 1400 m) and following gradual ascent to 5050 m. Beat-by-beat haemodynamics (photoplethysmography) and MSNA (microneurography) were recorded lying supine. Indices of vascular sympathetic baroreflex function were determined from the relationship of diastolic blood pressure (DBP) and corresponding MSNA at rest (i.e. DBP 'operating pressure' and MSNA 'operating point'), as well as during a modified Oxford baroreflex test (i.e. 'gain'). Operating pressure and gain were unchanged for Lowlanders during HA exposure; however, the operating point was reset upwards (48 ± 16 vs. 22 ± 12 bursts 100 HB-1 , P = 0.001). Compared to Lowlanders at 5050 m, Sherpa had similar gain and operating pressure, although the operating point was lower (30 ± 13 bursts 100 HB-1 , P = 0.02); MSNA burst frequency was lower for Sherpa (22 ± 11 vs. 30 ± 9 bursts min-1 P = 0.03). Breathing 100% oxygen did not alter vascular sympathetic baroreflex function for either group at HA. For Lowlanders, upward baroreflex resetting promotes heightened sympathetic vasoconstrictor activity and maintains blood pressure stability, at least during early HA exposure; mechanisms other than peripheral chemoreflex activation could be involved. Sherpa adaptation appears to favour a lower sympathetic vasoconstrictor activity compared to Lowlanders for blood pressure homeostasis.
Collapse
Affiliation(s)
- Lydia L Simpson
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, Wales, UK
| | - Stephen A Busch
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Samuel J Oliver
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, Wales, UK
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia Okanagan, BC, Kelowna, Canada
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, UK
| | - Craig D Steinback
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, Wales, UK
| |
Collapse
|
9
|
Tremblay JC, Hoiland RL, Carter HH, Howe CA, Stembridge M, Willie CK, Gasho C, MacLeod DB, Pyke KE, Ainslie PN. UBC-Nepal expedition: upper and lower limb conduit artery shear stress and flow-mediated dilation on ascent to 5,050 m in lowlanders and Sherpa. Am J Physiol Heart Circ Physiol 2018; 315:H1532-H1543. [PMID: 30168724 DOI: 10.1152/ajpheart.00345.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The study of conduit artery endothelial adaptation to hypoxia has been restricted to the brachial artery, and comparisons with highlanders have been confounded by differences in altitude exposure, exercise, and unknown levels of blood viscosity. To address these gaps, we tested the hypothesis that lowlanders, but not Sherpa, would demonstrate decreased mean shear stress and increased retrograde shear stress and subsequently reduced flow-mediated dilation (FMD) in the upper and lower limb conduit arteries on ascent to 5,050 m. Healthy lowlanders (means ± SD, n = 22, 28 ± 6 yr) and Sherpa ( n = 12, 34 ± 11 yr) ascended over 10 days, with measurements taken on nontrekking days at 1,400 m (baseline), 3,440 m ( day 4), 4,371 m ( day 7), and 5,050 m ( day 10). Arterial blood gases, blood viscosity, shear stress, and FMD [duplex ultrasound of the brachial and superficial femoral arteries (BA and SFA, respectively)] were acquired at each time point. Ascent decreased mean and increased retrograde shear stress in the upper and lower limb of lowlanders and Sherpa. Although BA FMD decreased in lowlanders from 7.1 ± 3.9% to 3.8 ± 2.8% at 5,050 versus 1,400 m ( P < 0.001), SFA FMD was preserved. In Sherpa, neither BA nor SFA FMD were changed upon ascent to 5,050 m. In lowlanders, the ascent-related exercise may favorably influence endothelial function in the active limb (SFA); selective impairment in FMD in the BA in lowlanders is likely mediated via the low mean or high oscillatory baseline shear stress. In contrast, Sherpa presented protected endothelial function, suggesting a potential vascular aspect of high-altitude acclimatization/adaptation. NEW & NOTEWORTHY Upper and lower limb arterial shear stress and flow-mediated dilation (FMD) were assessed on matched ascent from 1,400 to 5,050 m in lowlanders and Sherpa. A shear stress pattern associated with vascular dysfunction/risk manifested in both limbs of lowlanders and Sherpa. FMD was impaired only in the upper limb of lowlanders. The findings indicate a limb-specific impact of high-altitude trekking on FMD and a vascular basis to acclimatization wherein endothelial function is protected in Sherpa on ascent.
Collapse
Affiliation(s)
- Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University , Kingston, Ontario , Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Howard H Carter
- Department of Nutrition, Exercise and Sports, University of Copenhagen , Copenhagen , Denmark
| | - Connor A Howe
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University , Cardiff , United Kingdom
| | - Christopher K Willie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Christopher Gasho
- Division of Pulmonary, Critical Care, Hyperbaric and Sleep Medicine, Loma Linda University School of Medicine , Loma Linda, California
| | - David B MacLeod
- Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center , Durham, North Carolina
| | - Kyra E Pyke
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University , Kingston, Ontario , Canada
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| |
Collapse
|
10
|
Tremblay JC, Howe CA, Ainslie PN, Pyke KE. UBC-Nepal Expedition: imposed oscillatory shear stress does not further attenuate flow-mediated dilation during acute and sustained hypoxia. Am J Physiol Heart Circ Physiol 2018. [PMID: 29522371 DOI: 10.1152/ajpheart.00717.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Experimentally induced oscillatory shear stress (OSS) and hypoxia reduce endothelial function in humans. Acute and sustained hypoxia may cause increases in resting OSS; however, whether this influences endothelial susceptibility to further increases in OSS is unknown. Healthy lowlanders ( n = 15, 30 ± 6 yr; means ± SD) participated in three OSS interventions: two interventions at sea level [normoxia and after 20 min of normobaric hypoxia (acute hypoxia, 11% O2)] and one intervention 5-7 days after a 9-day ascent to 5,050 m (sustained hypoxia). OSS was provoked in the brachial artery using a 30-min distal cuff inflation (75 mmHg). Endothelial function was assessed before and after each intervention by reactive hyperemia flow-mediated dilation (FMD). Shear stress magnitude and patterns were obtained via Duplex ultrasound. Baseline retrograde shear stress and OSS were greater in acute hypoxia versus normoxia ( P < 0.001), and OSS was elevated in sustained hypoxia versus normoxia ( P = 0.011). The intervention further augmented OSS during each condition. Preintervention FMD was decreased by 29 ± 48% in acute hypoxia and by 25 ± 31% in sustained hypoxia compared with normoxia ( P = 0.001 and 0.026); these changes correlated with changes in baseline mean and antegrade shear stress. After the intervention, FMD decreased during normoxia (-41 ± 26%, P < 0.001) and was unaltered during acute or sustained hypoxia. Therefore, a 30-min exposure to OSS reduced FMD during normoxia, a condition with an unchallenged, healthy endothelium; however, imposed OSS did not appear to worsen endothelial function during acute or sustained hypoxia. Exposure to an altered magnitude and pattern of shear stress at baseline in hypoxia may contribute to the insensitivity to further acute augmentation of OSS. NEW & NOTEWORTHY We investigated whether the endothelium remains sensitive to experimental increases in oscillatory shear stress in acute (11% O2) and sustained (2 wk at 5,050 m) hypoxia. Hypoxia altered baseline shear stress and decreased endothelial function (flow-mediated dilation); however, exposure to experimentally induced oscillatory shear stress only impaired flow-mediated dilation in normoxia.
Collapse
Affiliation(s)
- Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University , Kingston, Ontario , Canada
| | - Connor A Howe
- Centre for Heart, Lung, and Vascular Health, University of British Columbia , Kelowna, British Columbia , Canada
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia , Kelowna, British Columbia , Canada
| | - Kyra E Pyke
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University , Kingston, Ontario , Canada
| |
Collapse
|
11
|
Ujka K, Bruno RM, Bastiani L, Bernardi E, Sdringola P, Dikic N, Basyal B, Bhandari SS, Basnyat B, Cogo A, Pratali L. Relationship Between Occupational Physical Activity and Subclinical Vascular Damage in Moderate-Altitude Dwellers. High Alt Med Biol 2017; 18:249-257. [PMID: 28876129 DOI: 10.1089/ham.2016.0104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Ujka, Kristian, Rosa Maria Bruno, Luca Bastiani, Eva Bernardi, Paolo Sdringola, Nenad Dikic, Bikash Basyal, Sanjeeb Sundarshan Bhandari, Buddha Basnyat, Annalisa Cogo, and Lorenza Pratali. Relationship between occupational physical activity and subclinical vascular damage in moderate-altitude dwellers. High Alt Med Biol. 18:249-257, 2017. BACKGROUND Occupational physical activity (OPA) has been associated with increased cardiovascular (CV) events. The aim of this study was to investigate the association between OPA and markers of subclinical vascular damage among a moderate-altitude population living in the rural village of Chaurikharka (Nepal; 2600 m sea level). METHODS Seventy-two individuals (age 42 ± 15 years, ranges 15-85 years, 23 men) were enrolled. Physical activity (PA) was evaluated using the International Physical Activity Questionnaire (IPAQ). Carotid-femoral pulse wave velocity (PWV), carotid ultrasound assessment, and flow-mediated dilation (FMD) were performed. RESULTS OPA was 9860 ± 5385 Metabolic Equivalent of Task (MET)-minutes/week, representing 77% of total energy expenditure, with 97% of the population performing high-intensity PA. In the univariate analysis, OPA was significantly associated with PWV (β = 0.474, p = 0.001) and carotid stiffness (CS) (β = 0.29, p = 0.019). In the multivariate analysis, including age, sex, oxygen saturation, mean blood pressure, low-density lipoprotein (LDL), and OPA, OPA remained an independent predictor of PWV (β = 0.403, p = 0.001) but not of CS (β = 0.028, p = 0.8). OPA remained an independent predictor of PWV independently from the Framingham risk score (FRS). CONCLUSION High-intensity OPA shows a positive, independent association with aortic stiffness in Himalayan moderate-altitude dwellers. This study suggests how vigorous OPA performed in moderate altitude may be a CV risk factor.
Collapse
Affiliation(s)
- Kristian Ujka
- 1 Institute of Clinical Physiology-CNR , Pisa, Italy
| | - Rosa Maria Bruno
- 1 Institute of Clinical Physiology-CNR , Pisa, Italy .,2 Department of Clinical and Experimental Medicine, University of Pisa , Pisa, Italy
| | - Luca Bastiani
- 1 Institute of Clinical Physiology-CNR , Pisa, Italy
| | - Eva Bernardi
- 3 Department of Clinical and Experimental Medicine, University of Ferrara , Ferrara, Italy
| | - Paolo Sdringola
- 4 Department of Engineering, University of Perugia , Perugia, Italy
| | | | | | | | | | - Annalisa Cogo
- 3 Department of Clinical and Experimental Medicine, University of Ferrara , Ferrara, Italy
| | | |
Collapse
|
12
|
Tymko MM, Tremblay JC, Steinback CD, Moore JP, Hansen AB, Patrician A, Howe CA, Hoiland RL, Green DJ, Ainslie PN. UBC-Nepal Expedition: acute alterations in sympathetic nervous activity do not influence brachial artery endothelial function at sea level and high altitude. J Appl Physiol (1985) 2017; 123:1386-1396. [PMID: 28860174 DOI: 10.1152/japplphysiol.00583.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 08/09/2017] [Accepted: 08/25/2017] [Indexed: 01/08/2023] Open
Abstract
Evidence indicates that increases in sympathetic nervous activity (SNA), and acclimatization to high altitude (HA), may reduce endothelial function as assessed by brachial artery flow-mediated dilatation (FMD); however, it is unclear whether such changes in FMD are due to direct vascular constraint, or consequential altered hemodynamics (e.g., shear stress) associated with increased SNA as a consequence of exposure to HA. We hypothesized that 1) at rest, SNA would be elevated and FMD would be reduced at HA compared with sea-level (SL); and 2) at SL and HA, FMD would be reduced when SNA was acutely increased, and elevated when SNA was acutely decreased. Using a novel, randomized experimental design, brachial artery FMD was assessed at SL (344 m) and HA (5,050 m) in 14 participants during mild lower-body negative pressure (LBNP; -10 mmHg) and lower-body positive pressure (LBPP; +10 mmHg). Blood pressure (finger photoplethysmography), heart rate (electrocardiogram), oxygen saturation (pulse oximetry), and brachial artery blood flow and shear rate (Duplex ultrasound) were recorded during LBNP, control, and LBPP trials. Muscle SNA was recorded (via microneurography) in a subset of participants (n = 5). Our findings were 1) at rest, SNA was elevated (P < 0.01), and absolute FMD was reduced (P = 0.024), but relative FMD remained unaltered (P = 0.061), at HA compared with SL; and 2) despite significantly altering SNA with LBNP (+60.3 ± 25.5%) and LBPP (-37.2 ± 12.7%) (P < 0.01), FMD was unaltered at SL (P = 0.448) and HA (P = 0.537). These data indicate that acute and mild changes in SNA do not directly influence brachial artery FMD at SL or HA.NEW & NOTEWORTHY The role of the sympathetic nervous system on endothelial function remains unclear. We used lower-body negative and positive pressure to manipulate sympathetic nervous activity at sea level and high altitude and measured brachial endothelial function via flow-mediated dilation. We found that acutely altering sympathetic nervous activity had no effect on endothelial function.
Collapse
Affiliation(s)
- Michael M Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada;
| | - Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Craig D Steinback
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Gwynedd, United Kingdom
| | - Alex B Hansen
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | | | - Connor A Howe
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Daniel J Green
- School of Sports Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia; and.,Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| |
Collapse
|
13
|
Tymko MM, Tremblay JC, Hansen AB, Howe CA, Willie CK, Stembridge M, Green DJ, Hoiland RL, Subedi P, Anholm JD, Ainslie PN. The effect of α 1 -adrenergic blockade on post-exercise brachial artery flow-mediated dilatation at sea level and high altitude. J Physiol 2016; 595:1671-1686. [PMID: 28032333 DOI: 10.1113/jp273183] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 11/01/2016] [Indexed: 12/27/2022] Open
Abstract
KEY POINTS Our objective was to quantify endothelial function (via brachial artery flow-mediated dilatation) at sea level (344 m) and high altitude (3800 m) at rest and following both maximal exercise and 30 min of moderate-intensity cycling exercise with and without administration of an α1 -adrenergic blockade. Brachial endothelial function did not differ between sea level and high altitude at rest, nor following maximal exercise. At sea level, endothelial function decreased following 30 min of moderate-intensity exercise, and this decrease was abolished with α1 -adrenergic blockade. At high altitude, endothelial function did not decrease immediately after 30 min of moderate-intensity exercise, and administration of α1 -adrenergic blockade resulted in an increase in flow-mediated dilatation. Our data indicate that post-exercise endothelial function is modified at high altitude (i.e. prolonged hypoxaemia). The current study helps to elucidate the physiological mechanisms associated with high-altitude acclimatization, and provides insight into the relationship between sympathetic nervous activity and vascular endothelial function. ABSTRACT We examined the hypotheses that (1) at rest, endothelial function would be impaired at high altitude compared to sea level, (2) endothelial function would be reduced to a greater extent at sea level compared to high altitude after maximal exercise, and (3) reductions in endothelial function following moderate-intensity exercise at both sea level and high altitude are mediated via an α1 -adrenergic pathway. In a double-blinded, counterbalanced, randomized and placebo-controlled design, nine healthy participants performed a maximal-exercise test, and two 30 min sessions of semi-recumbent cycling exercise at 50% peak output following either placebo or α1 -adrenergic blockade (prazosin; 0.05 mg kg -1 ). These experiments were completed at both sea-level (344 m) and high altitude (3800 m). Blood pressure (finger photoplethysmography), heart rate (electrocardiogram), oxygen saturation (pulse oximetry), and brachial artery blood flow and shear rate (ultrasound) were recorded before, during and following exercise. Endothelial function assessed by brachial artery flow-mediated dilatation (FMD) was measured before, immediately following and 60 min after exercise. Our findings were: (1) at rest, FMD remained unchanged between sea level and high altitude (placebo P = 0.287; prazosin: P = 0.110); (2) FMD remained unchanged after maximal exercise at sea level and high altitude (P = 0.244); and (3) the 2.9 ± 0.8% (P = 0.043) reduction in FMD immediately after moderate-intensity exercise at sea level was abolished via α1 -adrenergic blockade. Conversely, at high altitude, FMD was unaltered following moderate-intensity exercise, and administration of α1 -adrenergic blockade elevated FMD (P = 0.032). Our results suggest endothelial function is differentially affected by exercise when exposed to hypobaric hypoxia. These findings have implications for understanding the chronic impacts of hypoxaemia on exercise, and the interactions between the α1 -adrenergic pathway and endothelial function.
Collapse
Affiliation(s)
- Michael M Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Joshua C Tremblay
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Alex B Hansen
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Connor A Howe
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Chris K Willie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, UK
| | - Daniel J Green
- School of Sports Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia.,Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, UK
| | - Ryan L Hoiland
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Prajan Subedi
- Pulmonary/Critical Care Section, Medical Service, VA Loma Linda Healthcare System, Loma Linda, CA, USA
| | - James D Anholm
- Pulmonary/Critical Care Section, Medical Service, VA Loma Linda Healthcare System, Loma Linda, CA, USA
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| |
Collapse
|
14
|
Tremblay JC, Thom SR, Yang M, Ainslie PN. Oscillatory shear stress, flow-mediated dilatation, and circulating microparticles at sea level and high altitude. Atherosclerosis 2016; 256:115-122. [PMID: 28010936 DOI: 10.1016/j.atherosclerosis.2016.12.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 11/25/2016] [Accepted: 12/01/2016] [Indexed: 12/01/2022]
Abstract
BACKGROUND AND AIMS Exposing the endothelium to acute periods of imposed oscillatory shear stress reduces endothelial function and elevates circulating microparticles (MPs). Oscillatory shear stress may be especially pathogenic when superimposed on hypoxia, an environmental stimulus that disrupts the endothelial milieu. We examined the effects of acute manipulation of oscillatory shear stress on endothelial function and circulating MPs at sea level (SL) and high altitude (HA). METHODS Healthy adults (n = 12) participated, once at SL and once on the second or third day at HA (3800 m). Oscillatory shear stress was provoked using a 30-min distal cuff occlusion intervention (75 mmHg). Endothelial function was assessed before and immediately after the intervention in the brachial artery by reactive hyperaemia flow-mediated dilatation (FMD). Venous blood samples of MPs (flow cytometry) were obtained before and during the last five minutes of the shear intervention. RESULTS At baseline, circulating MPs were two-fold higher at HA (p = 0.011) and brachial artery diameter was constricted (p = 0.015). Although the intervention at SL increased endothelial-derived MPs by 83 ± 39% (mean ± SEM; p = 0.021), FMD was unaltered. Conversely, at HA, the intervention elicited a 26 ± 11% reduction in FMD (p = 0.020); this reduction was inversely correlated with the change in total circulating MPs (r = -0.737, p = 0.006) and the change in endothelial-derived MPs (r = -0.614, p = 0.034). CONCLUSIONS The vascular endothelium appears to be susceptible to periods of oscillatory shear stress at HA, where impairments in endothelium-dependent vasodilatation may be amplified by endothelial injury. These findings have important implications for understanding the early impact of clinical situations of hypoxaemia on the vascular endothelium.
Collapse
Affiliation(s)
- Joshua C Tremblay
- Centre for Heart, Lung, and Vascular Health School of Health and Exercise Science, University of British Columbia, Kelowna, Canada.
| | - Stephen R Thom
- Department of Emergency Medicine, University of Maryland, Baltimore, USA
| | - Ming Yang
- Department of Emergency Medicine, University of Maryland, Baltimore, USA
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| |
Collapse
|