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Karimpour P, Ferizoli R, May JM, Kyriacou PA. Customisable Silicone Vessels and Tissue Phantoms for In Vitro Photoplethysmography Investigations into Cardiovascular Disease. Sensors (Basel) 2024; 24:1681. [PMID: 38475217 DOI: 10.3390/s24051681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 02/23/2024] [Accepted: 03/02/2024] [Indexed: 03/14/2024]
Abstract
Age-related vessel deterioration leads to changes in the structure and function of the heart and blood vessels, notably stiffening of vessel walls, increasing the risk of developing cardiovascular disease (CVD), which accounts for 17.9 million global deaths annually. This study describes the fabrication of custom-made silicon vessels with varying mechanical properties (arterial stiffness). The primary objective of this study was to explore how changes in silicone formulations influenced vessel properties and their correlation with features extracted from signals obtained from photoplethysmography (PPG) reflectance sensors in an in vitro setting. Through alterations in the silicone formulations, it was found that it is possible to create elastomers exhibiting an elasticity range of 0.2 MPa to 1.22 MPa. It was observed that altering vessel elasticity significantly impacted PPG signal morphology, particularly reducing amplitude with increasing vessel stiffness (p < 0.001). A p-value of 5.176 × 10-15 and 1.831 × 10-14 was reported in the red and infrared signals, respectively. It has been concluded in this study that a femoral artery can be recreated using the silicone material, with the addition of a softener to achieve the required mechanical properties. This research lays the foundation for future studies to replicate healthy and unhealthy vascular systems. Additional pathologies can be introduced by carefully adjusting the elastomer materials or incorporating geometrical features consistent with various CVDs.
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Affiliation(s)
- Parmis Karimpour
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, UK
| | - Redjan Ferizoli
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, UK
| | - James M May
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, UK
| | - Panicos A Kyriacou
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, UK
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Ferizoli R, Karimpour P, May JM, Kyriacou PA. Arterial stiffness assessment using PPG feature extraction and significance testing in an in vitro cardiovascular system. Sci Rep 2024; 14:2024. [PMID: 38263412 PMCID: PMC10806047 DOI: 10.1038/s41598-024-51395-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 01/04/2024] [Indexed: 01/25/2024] Open
Abstract
Cardiovascular diseases (CVDs) remain the leading cause of global mortality, therefore understanding arterial stiffness is essential to developing innovative technologies to detect, monitor and treat them. The ubiquitous spread of photoplethysmography (PPG), a completely non-invasive blood-volume sensing technology suitable for all ages, highlights immense potential for arterial stiffness assessment in the wider healthcare setting outside specialist clinics, for example during routine visits to a General Practitioner or even at home with the use of mobile and wearable health devices. This study employs a custom-manufactured in vitro cardiovascular system with vessels of varying stiffness to test the hypothesis that PPG signals may be used to detect and assess the level of arterial stiffness under controlled conditions. Analysis of various morphological features demonstrated significant (p < 0.05) correlations with vessel stiffness. Particularly, area related features were closely linked to stiffness in red PPG signals, while for infrared PPG signals the most correlated features were related to pulse-width. This study demonstrates the utility of custom vessels and in vitro investigations to work towards non-invasive cardiovascular assessment using PPG, a valuable tool with applications in clinical healthcare, wearable health devices and beyond.
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Affiliation(s)
- Redjan Ferizoli
- Research Centre for Biomedical Engineering, City, University of London, London, EC1V 0HB, UK.
| | - Parmis Karimpour
- Research Centre for Biomedical Engineering, City, University of London, London, EC1V 0HB, UK
| | - James M May
- Research Centre for Biomedical Engineering, City, University of London, London, EC1V 0HB, UK
| | - Panicos A Kyriacou
- Research Centre for Biomedical Engineering, City, University of London, London, EC1V 0HB, UK
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Karimpour P, May JM, Kyriacou PA. Photoplethysmography for the Assessment of Arterial Stiffness. Sensors (Basel) 2023; 23:9882. [PMID: 38139728 PMCID: PMC10747425 DOI: 10.3390/s23249882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/08/2023] [Accepted: 12/13/2023] [Indexed: 12/24/2023]
Abstract
This review outlines the latest methods and innovations for assessing arterial stiffness, along with their respective advantages and disadvantages. Furthermore, we present compelling evidence indicating a recent growth in research focused on assessing arterial stiffness using photoplethysmography (PPG) and propose PPG as a potential tool for assessing vascular ageing in the future. Blood vessels deteriorate with age, losing elasticity and forming deposits. This raises the likelihood of developing cardiovascular disease (CVD), widely reported as the global leading cause of death. The ageing process induces structural modifications in the vascular system, such as increased arterial stiffness, which can cause various volumetric, mechanical, and haemodynamic alterations. Numerous techniques have been investigated to assess arterial stiffness, some of which are currently used in commercial medical devices and some, such as PPG, of which still remain in the research space.
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Affiliation(s)
| | | | - Panicos A. Kyriacou
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, UK; (P.K.); (J.M.M.)
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May JM, Nomoni M, Budidha K, Choi C, Kyriacou PA. Mechanical Testing of Artificial Vessels and Tissues for Photoplethysmography Phantoms. Annu Int Conf IEEE Eng Med Biol Soc 2022; 2022:629-632. [PMID: 36086013 DOI: 10.1109/embc48229.2022.9871830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Various studies have looked at the efficiency of artificial vessel and tissue networks in the study of photoplethysmography (PPG) in an effort to better understand the origin of various morphological features present in the signal. Whilst there are all reasonable attempts made to replicate geometrical features such as vessel depth, vessel wall thickness and diameter etc., not many studies have attempted to replicate the mechanical properties such as vessel elasticity and tissue compressibility. This study reports two methods for tissue mechanical testing for the analysis of vessel elasticity and tissue compressibility. A two-part polydimethylsiloxane (PDMS) was used as a base material for both tissue and vessel construction, and the properties altered by changing the curing component ratio. Tissue compression properties were investigated using an industrially calibrated materials testing device using the protocol from the ASTM 0575-91 testing method. Vessel elasticity was investigated using a custom method and apparatus to report vessel diameter and length change simultaneously. Tissue compressive properties proved reasonably easy to replicate through catalyst alteration, however the vessel elasticity properties were found to be higher than expected at all reasonable catalyst ratios. The property of hyper-elasticity was observed in the artificial vessels though, leading to the conclusion that alternative material recipes or construction methods may be needed to correctly replicate the expected mechanical characteristics. Clinical Relevance- The latest generation of health monitoring devices, especially those that are wearable and used widely by individuals wishing to monitor their health daily are becoming smarter and more sophisticated in their functionality. The majority of such devices use photoplethysmography (PPG) as their primary monitoring technique. Being able to replicate the PPG in a phantom allows the continued study and development of devices, and to improve their functionality without the continued need for extensive user-testing.
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Mejía-Mejía E, May JM, Kyriacou PA. Effects of using different algorithms and fiducial points for the detection of interbeat intervals, and different sampling rates on the assessment of pulse rate variability from photoplethysmography. Comput Methods Programs Biomed 2022; 218:106724. [PMID: 35255373 DOI: 10.1016/j.cmpb.2022.106724] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 02/28/2022] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
OBJECTIVE Pulse Rate Variability (PRV) has been widely used as a surrogate of Heart Rate Variability (HRV). However, there are several technical aspects that may affect the extraction of PRV information from pulse wave signals such as the photoplethysmogram (PPG). The aim of this study was to evaluate the effects of changing the algorithm and fiducial points used for determining inter-beat intervals (IBIs), as well as the PPG sampling rate, from simulated PPG signals with known PRV content. METHODS PPG signals were simulated using a proposed model, in which PRV information can be modelled. Two independent experiments were performed. First, 5 IBIs detection algorithms and 8 fiducial points were used for assessing PRV information from the simulated PPG signals, and time-domain and Poincaré plot indices were extracted and compared to the expected values according to the simulated PRV. The best combination of algorithms and fiducial points were determined for each index, using factorial designs. Then, using one of the best combinations, PPG signals were simulated with varying sampling rates. PRV indices were extracted and compared to the expected values using Student t-tests or Mann-Whitney U-tests. RESULTS From the first experiment, it was observed that AVNN and SD2 indices behaved similarly, and there was no significant influence of the fiducial points used. For other indices, there were several combinations that behaved similarly well, mostly based on the detection of the valleys of the PPG signal. There were differences according to the quality of the PPG signal. From the second experiment, it was observed that, for all indices but SDNN, the higher the sampling rate the better. AVNN and SD2 showed no statistical differences even at the lowest evaluated sampling rate (32 Hz), while RMSSD, pNN50, S, SD1 and SD1/SD2 showed good performance at sampling rates as low as 128 Hz. CONCLUSION The best combination of IBIs detection algorithms and fiducial points differs according to the application, but those based on the detection of the valleys of the PPG signal tend to show a better performance. The sampling rate of PPG signals for PRV analysis could be lowered to around 128 Hz, although it could be further lowered according to the application. SIGNIFICANCE The standardisation of PRV analysis could increase the reliability of this signal and allow for the comparison of results obtained from different studies. The obtained results allow for a first approach to establish guidelines for two important aspects in PRV analysis from PPG signals, i.e. the way the IBIs are segmented from PPG signals, and the sampling rate that should be used for these analyses. Moreover, a model for simulating PPG signals with PRV information has been proposed, which allows for the establishing of these guidelines while controlling for other variables, such as the quality of the PPG signal.
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Affiliation(s)
- Elisa Mejía-Mejía
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom.
| | - James M May
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom
| | - Panayiotis A Kyriacou
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom
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Pilt K, May JM, Kyriacou PA. In-Vitro Investigation of Flow Profiles in Arteries Using the Photoplethysmograph. Annu Int Conf IEEE Eng Med Biol Soc 2021; 2021:7211-7214. [PMID: 34892763 DOI: 10.1109/embc46164.2021.9629713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The flow profile in the artery reflects the health status of the vessel and generally the arterial system. The aim of this pilot study was to investigate in-vitro the effect of flow profiles on reflective photoplethysmography (PPG) signals at different steady state flow rates and levels of vessel constrictions. A simplified model of an arterial system was built, consisting of a steady state flow gear pump, PVC vinyl tubing, reservoir and a clamp with a micrometer gauge. The blood mimicking fluid (2.5% India ink and water solution) was pumped through the model. It was found that the waveforms of the PPG signals fluctuate irregularly and the magnitude of the frequency components was increased below 60 Hz in cases of turbulent flow (Re = 2503). These preliminary results suggest that PPG could be the basis for new technologies for assessing the profile of the blood flow in the artery. Future studies have to be carried out with pulsatile flow and more complex models that are more similar to the human arterial system.Clinical Relevance- The PPG signal reflects changes in the flow profile caused by the stenotic rigid vessel.
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Mejia-Mejia E, May JM, Kyriacou PA. Effect of Filtering of Photoplethysmography Signals in Pulse Rate Variability Analysis . Annu Int Conf IEEE Eng Med Biol Soc 2021; 2021:5500-5503. [PMID: 34892370 DOI: 10.1109/embc46164.2021.9629521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Due to the widespread use and simplicity of photoplethysmography (PPG) signals, and because this signal contains information related to pulse rate, several studies have started to propose the use of Pulse Rate Variability (PRV) for the assessment of cardiovascular autonomic nervous activity, instead of using Heart Rate Variability (HRV) obtained with the electrocardiogram (ECG). However, there is a lack of standardisation and guidelines for the measurement of PRV from PPG signals, which might hinder comparability among studies and validation of results. The aim of this study was to evaluate different digital filters on PPG signals and their effects on PRV information, compared to HRV obtained from ECG. PPG and ECG signals obtained from healthy volunteers were used to measure HRV and PRV. PPG signals were filtered using different FIR and IIR digital filters, with several cut-off frequencies. The results indicate that filtering PPG signals using IIR filters and lower low-cut-off frequencies allow for the acquisition of more reliable PRV information, with lower Bland-Altman ratios and higher cross-correlations when compared to HRV. This is a first step in establishing guidelines and standards for the analysis of PRV information using PPG signals.Clinical relevance- Pulse rate variability might be a useful tool for the assessment of the cardiovascular autonomic nervous system. This study is the first step for establishing standards of measurement of this signal, which helps in the comparability and validation of the technique.
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Mejía-Mejía E, May JM, Elgendi M, Kyriacou PA. Classification of blood pressure in critically ill patients using photoplethysmography and machine learning. Comput Methods Programs Biomed 2021; 208:106222. [PMID: 34166851 DOI: 10.1016/j.cmpb.2021.106222] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 05/26/2021] [Indexed: 06/13/2023]
Abstract
OBJECTIVE The aim of this study was to evaluate the capability of features extracted from photoplethysmography (PPG) based Pulse Rate Variability (PRV) to classify hypertensive, normotensive and hypotensive events, and to estimate mean arterial, systolic and diastolic blood pressure in critically ill patients. METHODS Time-domain, frequency-domain and non-linear indices from PRV were extracted from 5-min and 1-min segments obtained from PPG signals. These features were filtered using machine learning algorithms in order to obtain the optimal combination for the classification of hypertensive, hypotensive and normotensive events, and for the estimation of blood pressure. RESULTS 5-min segments allowed for an improved performance in both classification and estimation tasks. Classification of blood pressure states showed around 70% accuracy and around 75% specificity. The sensitivity, precision and F1 scores were around 50%. In estimating mean arterial, systolic, and diastolic blood pressure, mean absolute errors as low as 2.55 ± 0.78 mmHg, 4.74 ± 2.33 mmHg, and 1.78 ± 0.14 mmHg were obtained, respectively. Bland-Altman analysis and Wilcoxon rank sum tests showed good agreement between real and estimated values, especially for mean and diastolic arterial blood pressures. CONCLUSION PRV-based features could be used for the classification of blood pressure states and the estimation of blood pressure values, although including additional features from the PPG waveform could improve the results. SIGNIFICANCE PRV contains information related to blood pressure, which may aid in the continuous, noninvasive, non-intrusive estimation of blood pressure and detection of hypertensive and hypotensive events in critically ill subjects.
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Affiliation(s)
- Elisa Mejía-Mejía
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom.
| | - James M May
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom
| | | | - Panayiotis A Kyriacou
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom
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Wilcox JM, Consoli DC, Tienda AA, Dixit S, Buchanan RA, May JM, Nobis WP, Harrison FE. Altered synaptic glutamate homeostasis contributes to cognitive decline in young APP/PSEN1 mice. Neurobiol Dis 2021; 158:105486. [PMID: 34450329 PMCID: PMC8457528 DOI: 10.1016/j.nbd.2021.105486] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 08/10/2021] [Accepted: 08/16/2021] [Indexed: 12/02/2022] Open
Abstract
Non-convulsive epileptiform activity is a common and under-studied comorbidity of Alzheimer’s disease that may significantly contribute to onset of clinical symptoms independently of other neuropathological features such as β-amyloid deposition. We used repeated treatment with low dose kainic acid (KA) to trigger subthreshold epileptiform activity in young (less than 6 months) wild-type (WT) and APP/PSEN1 mice to test the role of disruption to the glutamatergic system in epileptiform activity changes and the development of memory deficits. Short-term repeated low-dose KA (five daily treatments with 5 mg/kg, IP) impaired long-term potentiation in hippocampus of APP/PSEN1 but not WT mice. Long-term repeated low-dose KA (fourteen weeks of bi-weekly treatment with 7.5–10 mg/kg) led to high mortality in APP/PSEN1 mice. KA treatment also impaired memory retention in the APP/PSEN1 mice in a Morris water maze task under cognitively challenging reversal learning conditions where the platform was moved to a new location. Four weeks of bi-weekly treatment with 5 mg/kg KA also increased abnormal spike activity in APP/PSEN1 and not WT mice but did not impact sleep/wake behavioral states. These findings suggest that hyperexcitability in Alzheimer’s disease may indeed be an early contributor to cognitive decline that is independent of heavy β-amyloid-plaque load, which is absent in APP/PSEN1 mice under 6 months of age.
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Affiliation(s)
- J M Wilcox
- Program in Neuroscience, Vanderbilt University, Nashville, TN, United States of America; Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - D C Consoli
- Program in Neuroscience, Vanderbilt University, Nashville, TN, United States of America
| | - A A Tienda
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - S Dixit
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - R A Buchanan
- Program in Neuroscience, Vanderbilt University, Nashville, TN, United States of America
| | - J M May
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - W P Nobis
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - F E Harrison
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, United States of America.
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Mejía-Mejía E, May JM, Elgendi M, Kyriacou PA. Differential effects of the blood pressure state on pulse rate variability and heart rate variability in critically ill patients. NPJ Digit Med 2021; 4:82. [PMID: 33990692 PMCID: PMC8121822 DOI: 10.1038/s41746-021-00447-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/16/2021] [Indexed: 02/06/2023] Open
Abstract
Heart rate variability (HRV) utilizes the electrocardiogram (ECG) and has been widely studied as a non-invasive indicator of cardiac autonomic activity. Pulse rate variability (PRV) utilizes photoplethysmography (PPG) and recently has been used as a surrogate for HRV. Several studies have found that PRV is not entirely valid as an estimation of HRV and that several physiological factors, including the pulse transit time (PTT) and blood pressure (BP) changes, may affect PRV differently than HRV. This study aimed to assess the relationship between PRV and HRV under different BP states: hypotension, normotension, and hypertension. Using the MIMIC III database, 5 min segments of PPG and ECG signals were used to extract PRV and HRV, respectively. Several time-domain, frequency-domain, and nonlinear indices were obtained from these signals. Bland–Altman analysis, correlation analysis, and Friedman rank sum tests were used to compare HRV and PRV in each state, and PRV and HRV indices were compared among BP states using Kruskal–Wallis tests. The findings indicated that there were differences between PRV and HRV, especially in short-term and nonlinear indices, and although PRV and HRV were altered in a similar manner when there was a change in BP, PRV seemed to be more sensitive to these changes.
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Affiliation(s)
- Elisa Mejía-Mejía
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom.
| | - James M May
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom
| | - Mohamed Elgendi
- Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Panayiotis A Kyriacou
- Research Centre for Biomedical Engineering, City, University of London, London, United Kingdom
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Mejia-Mejia E, Budidha K, Abay TY, May JM, Kyriacou PA. Heart Rate Variability and Multi-Site Pulse Rate Variability for the Assessment of Autonomic Responses to Whole-Body Cold Exposure. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2020:2618-2621. [PMID: 33018543 DOI: 10.1109/embc44109.2020.9175856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Heart rate variability (HRV) is a noninvasive marker of cardiac autonomic activity and has been used in different circumstances to assess the autonomic responses of the body. Pulse rate variability (PRV), a similar variable obtained from pulse waves, has been used in recent years as a valid surrogate of HRV. However, the effect that localized changes in autonomic activity have in the relationship between HRV and PRV has not been entirely understood. In this study, a whole-body cold exposure protocol was performed to generate localized changes in autonomic activity, and HRV and PRV from different body sites were obtained. PRV measured from the earlobe and the finger was shown to differ from HRV, and the correlation between these variables was affected by the cold. Also, it was found that PRV from the finger was more affected by cold exposure than PRV from the earlobe. In conclusion, PRV is affected differently to HRV when localized changes in autonomic activity occur. Hence, PRV should not be considered as a valid surrogate of HRV under certain circumstances.Clinical Relevance- This indicates that pulse rate variability is affected differently to heart rate variability when autonomic activity is modified and suggests that pulse rate variability is not always a valid surrogate of heart rate variability.
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Nomoni M, May JM, Kyriacou PA. Fabricating Novel PDMS Vessels for Phantoms in Photoplethysmography Investigations. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2020:4458-4461. [PMID: 33018984 DOI: 10.1109/embc44109.2020.9176476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This paper introduces a novel technique for the development of custom polydimethylsiloxane (PDMS) vessels for use in phantom technologies. The method involves continuous dip coating of commercial silicone tubes with rapid curation in a single controlled process. The technique accommodates the production of different vessel diameters, wall thicknesses (56 µm-80 µm) and mechanical properties. Clear phantoms were fabricated to compare the commercial silicone tubes against the customs vessels. A pulsatile fluidic pump (BDCLabs, CO, USA) driven by a computer controlled linear motor generated the pulsatile flow through the phantom. The resulting flow profile, using the custom vessels, simulates human blood flow and the detected contact PPG signal from the phantom closely resembles the morphology of in vivo PPG waveforms with signal-to-noise ratios of 38.16 dB and 40.59 dB, compared to the closest commercially-available tubing at 5.38 dB and 10.59 dB for the red and infrared wavelengths respectively. The rigidity and thick walls of commercial silicone tubes impede the expansion of the tubing under systolic pressure. This technique eliminates this common limitation in phantom development.
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Mejía-Mejía E, May JM, Torres R, Kyriacou PA. Pulse rate variability in cardiovascular health: a review on its applications and relationship with heart rate variability. Physiol Meas 2020; 41:07TR01. [DOI: 10.1088/1361-6579/ab998c] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Nomoni M, May JM, Kyriacou PA. Novel Polydimethylsiloxane (PDMS) Pulsatile Vascular Tissue Phantoms for the In-Vitro Investigation of Light Tissue Interaction in Photoplethysmography. Sensors (Basel) 2020; 20:E4246. [PMID: 32751541 PMCID: PMC7435705 DOI: 10.3390/s20154246] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 07/27/2020] [Accepted: 07/28/2020] [Indexed: 11/22/2022]
Abstract
Currently there exists little knowledge or work in phantoms for the in-vitro evaluation of photoplethysmography (PPG), and its' relationship with vascular mechanics. Such phantoms are needed to provide robust, basic scientific knowledge, which will underpin the current efforts in developing new PPG technologies for measuring or estimating blood pressure, blood flow and arterial stiffness, to name but a few. This work describes the design, fabrication and evaluation of finger tissue-simulating pulsatile phantoms with integrated custom vessels. A novel technique has been developed to produce custom polydimethylsiloxane (PDMS) vessels by a continuous dip-coating process. This process can accommodate the production of different sized vessel diameters (1400-2500 µm) and wall thicknesses (56-80 µm). These vessels were embedded into a mould with a solution of PDMS and India ink surrounding them. A pulsatile pump experimental rig was set up to test the phantoms, where flow rate (1-12 L·min-1), heart rate (40-120 bpm), and total resistance (0-100% resistance clamps) could be controlled on demand. The resulting flow profiles approximates human blood flow, and the detected contact PPG signal (red and infrared) from the phantom closely resembles the morphology of in-vivo PPG waveforms with signal-to-noise ratios of 38.16 and 40.59 dB, for the red and infrared wavelengths, respectively. The progress made by this phantom development will help in obtaining new knowledge in the behaviour of PPG's under differing flow conditions, optical tissue properties and differing vessel stiffness.
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Affiliation(s)
- Michelle Nomoni
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, UK; (J.M.M.); (P.A.K.)
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Mejía-Mejía E, Budidha K, Abay TY, May JM, Kyriacou PA. Heart Rate Variability (HRV) and Pulse Rate Variability (PRV) for the Assessment of Autonomic Responses. Front Physiol 2020; 11:779. [PMID: 32792970 PMCID: PMC7390908 DOI: 10.3389/fphys.2020.00779] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 06/15/2020] [Indexed: 12/29/2022] Open
Abstract
Introduction: Heart Rate Variability (HRV) and Pulse Rate Variability (PRV), are non-invasive techniques for monitoring changes in the cardiac cycle. Both techniques have been used for assessing the autonomic activity. Although highly correlated in healthy subjects, differences in HRV and PRV have been observed under various physiological conditions. The reasons for their disparities in assessing the degree of autonomic activity remains unknown. Methods: To investigate the differences between HRV and PRV, a whole-body cold exposure (CE) study was conducted on 20 healthy volunteers (11 male and 9 female, 30.3 ± 10.4 years old), where PRV indices were measured from red photoplethysmography signals acquired from central (ear canal, ear lobe) and peripheral sites (finger and toe), and HRV indices from the ECG signal. PRV and HRV indices were used to assess the effects of CE upon the autonomic control in peripheral and core vasculature, and on the relationship between HRV and PRV. The hypotheses underlying the experiment were that PRV from central vasculature is less affected by CE than PRV from the peripheries, and that PRV from peripheral and central vasculature differ with HRV to a different extent, especially during CE. Results: Most of the PRV time-domain and Poincaré plot indices increased during cold exposure. Frequency-domain parameters also showed differences except for relative-power frequency-domain parameters, which remained unchanged. HRV-derived parameters showed a similar behavior but were less affected than PRV. When PRV and HRV parameters were compared, time-domain, absolute-power frequency-domain, and non-linear indices showed differences among stages from most of the locations. Bland-Altman analysis showed that the relationship between HRV and PRV was affected by CE, and that it recovered faster in the core vasculature after CE. Conclusion: PRV responds to cold exposure differently to HRV, especially in peripheral sites such as the finger and the toe, and may have different information not available in HRV due to its non-localized nature. Hence, multi-site PRV shows promise for assessing the autonomic activity on different body locations and under different circumstances, which could allow for further understanding of the localized responses of the autonomic nervous system.
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Affiliation(s)
- Elisa Mejía-Mejía
- Research Centre for Biomedical Engineering (RCBE), School of Mathematics, Engineering and Computer Science, University of London, London, United Kingdom
| | - Karthik Budidha
- Research Centre for Biomedical Engineering (RCBE), School of Mathematics, Engineering and Computer Science, University of London, London, United Kingdom
| | - Tomas Ysehak Abay
- Research Centre for Biomedical Engineering (RCBE), School of Mathematics, Engineering and Computer Science, University of London, London, United Kingdom
| | - James M May
- Research Centre for Biomedical Engineering (RCBE), School of Mathematics, Engineering and Computer Science, University of London, London, United Kingdom
| | - Panayiotis A Kyriacou
- Research Centre for Biomedical Engineering (RCBE), School of Mathematics, Engineering and Computer Science, University of London, London, United Kingdom
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Nomoni M, May JM, Kyriacou PA. A Pulsatile Optical Tissue Phantom for the Investigation of Light-Tissue Interaction in Reflectance Photoplethysmography. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2019:3204-3207. [PMID: 31946569 DOI: 10.1109/embc.2019.8857036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The aim of this study was to investigate the effect of emitter-detector separation distance and arterial depth in reflectance photoplethysmography (PPG), utilizing a homogenous pulsatile phantom that exhibits the broad optical absorbance and scattering properties of human tissue. The developed phantom comprised of embedded silicone arteries (outer diameter = 4 mm) that were arranged parallel to one another at nine increasing depths (3.2 mm to 24.4 mm). A pulsatile pump (Harvard Apparatus, MA, USA) circulated a blood imitating fluid through the vessels at the desired heart rate (60 bpm) and stroke volume (5 Lmin-1). The PPG sensor's emitter and detector were isolated on a translation bridge to provide a computer-controlled separation distance between them. Recordings were taken at each vessel depth for emitter-detector separation distances from 2 mm to 8 mm in 0.1 mm steps. The optimum separation distance between the emitter and detector for vessels between depths of 3.2 mm and 10.5 mm was between 3.7 and 4.3 mm, suggesting that the maximum penetration of IR (930 nm) light in a homogenous pulsatile phantom is no greater than 10.5 mm.
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17
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Babaev VR, Ding L, Zhang Y, May JM, Ramsey SA, Vickers KC, Linton MF. Loss of 2 Akt (Protein Kinase B) Isoforms in Hematopoietic Cells Diminished Monocyte and Macrophage Survival and Reduces Atherosclerosis in Ldl Receptor-Null Mice. Arterioscler Thromb Vasc Biol 2019; 39:156-169. [PMID: 30567482 DOI: 10.1161/atvbaha.118.312206] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Objective- Macrophages express 3 Akt (protein kinase B) isoforms, Akt1, Akt2, and Akt3, which display isoform-specific functions but may be redundant in terms of Akt survival signaling. We hypothesize that loss of 2 Akt isoforms in macrophages will suppress their ability to survive and modulate the development of atherosclerosis. Approach and Results- To test this hypothesis, we reconstituted male Ldlr-/- mice with double Akt2/Akt3 knockout hematopoietic cells expressing only the Akt1 isoform (Akt1only). There were no differences in body weight and plasma lipid levels between the groups after 8 weeks of the Western diet; however, Akt1only→ Ldlr-/- mice developed smaller (57.6% reduction) atherosclerotic lesions with more apoptotic macrophages than control mice transplanted with WT (wild type) cells. Next, male and female Ldlr-/- mice were reconstituted with double Akt1/Akt2 knockout hematopoietic cells expressing the Akt3 isoform (Akt3only). Female and male Akt3only→ Ldlr-/- recipients had significantly smaller (61% and 41%, respectively) lesions than the control WT→ Ldlr-/- mice. Loss of 2 Akt isoforms in hematopoietic cells resulted in markedly diminished levels of white blood cells, B cells, and monocytes and compromised viability of monocytes and peritoneal macrophages compared with WT cells. In response to lipopolysaccharides, macrophages with a single Akt isoform expressed low levels of inflammatory cytokines; however, Akt1only macrophages were distinct in expressing high levels of antiapoptotic Il10 compared with WT and Akt3only cells. Conclusions- Loss of 2 Akt isoforms in hematopoietic cells, preserving only a single Akt1 or Akt3 isoform, markedly compromises monocyte and macrophage viability and diminishes early atherosclerosis in Ldlr-/- mice.
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Affiliation(s)
- Vladimir R Babaev
- From the Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., K.C.V., M.F.L.), Vanderbilt University School of Medicine, Nashville, TN
| | - Lei Ding
- From the Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., K.C.V., M.F.L.), Vanderbilt University School of Medicine, Nashville, TN
| | - Youmin Zhang
- From the Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., K.C.V., M.F.L.), Vanderbilt University School of Medicine, Nashville, TN
| | - James M May
- From the Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., K.C.V., M.F.L.), Vanderbilt University School of Medicine, Nashville, TN.,Department of Molecular Physiology and Biophysics (J.M.M., K.C.V.), Vanderbilt University School of Medicine, Nashville, TN
| | - Stephen A Ramsey
- Department of Biomedical Sciences, Oregon State University, School of Electrical Engineering and Computer Science, Corvallis (S.A.R.)
| | - Kasey C Vickers
- From the Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., K.C.V., M.F.L.), Vanderbilt University School of Medicine, Nashville, TN.,Department of Molecular Physiology and Biophysics (J.M.M., K.C.V.), Vanderbilt University School of Medicine, Nashville, TN
| | - MacRae F Linton
- From the Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., K.C.V., M.F.L.), Vanderbilt University School of Medicine, Nashville, TN.,Department of Pharmacology (M.F.L.), Vanderbilt University School of Medicine, Nashville, TN
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18
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May JM, Phillips JP, Fitchat T, Ramaswamy S, Snidvongs S, Kyriacou PA. A Novel Photoplethysmography Sensor for Vital Signs Monitoring from the Human Trachea. Biosensors (Basel) 2019; 9:E119. [PMID: 31581652 PMCID: PMC6956046 DOI: 10.3390/bios9040119] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 09/23/2019] [Accepted: 09/27/2019] [Indexed: 11/20/2022]
Abstract
Current pulse oximeter sensors can be challenged in working accurately and continuously in situations of reduced periphery perfusion, especially among anaesthetised patients. A novel tracheal photoplethysmography (PPG) sensor has been developed in an effort to address the limitations of current pulse oximeters. The sensor has been designed to estimate oxygen saturation (SpO2) and pulse rate, and has been manufactured on a flexible printed circuit board (PCB) that can adhere to a standard endotracheal (ET) tube. A pilot clinical trial was carried out as a feasibility study on 10 anaesthetised patients. Good quality PPGs from the trachea were acquired at red and infrared wavelengths in all patients. The mean SpO2 reading for the ET tube was 97.1% (SD 1.0%) vs. the clinical monitor at 98.7% (SD 0.7%). The mean pulse rate for the ET sensor was 65.4 bpm (SD 10.0 bpm) vs. the clinical monitor at 64.7 bpm (SD 9.9 bpm). This study supports the hypothesis that the human trachea could be a suitable monitoring site of SpO2 and other physiological parameters, at times where the periphery circulation might be compromised.
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Affiliation(s)
- James M May
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, EC1V 0HB, UK.
| | - Justin P Phillips
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, EC1V 0HB, UK.
| | | | | | | | - Panayiotis A Kyriacou
- Research Centre for Biomedical Engineering, City, University of London, London EC1V 0HB, EC1V 0HB, UK.
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19
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Babaev VR, Huang J, Ding L, Zhang Y, May JM, Linton MF. Loss of Rictor in Monocyte/Macrophages Suppresses Their Proliferation and Viability Reducing Atherosclerosis in LDLR Null Mice. Front Immunol 2018; 9:215. [PMID: 29487597 PMCID: PMC5816794 DOI: 10.3389/fimmu.2018.00215] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/25/2018] [Indexed: 12/23/2022] Open
Abstract
Background Rictor is an essential component of mammalian target of rapamycin (mTOR) complex 2 (mTORC2), a conserved serine/threonine kinase that may play a role in cell proliferation, survival and innate or adaptive immune responses. Genetic loss of Rictor inactivates mTORC2, which directly activates Akt S473 phosphorylation and promotes pro-survival cell signaling and proliferation. Methods and results To study the role of mTORC2 signaling in monocytes and macrophages, we generated mice with myeloid lineage-specific Rictor deletion (MRictor−/−). These MRictor−/− mice exhibited dramatic reductions of white blood cells, B-cells, T-cells, and monocytes but had similar levels of neutrophils compared to control Rictor flox-flox (Rictorfl/fl) mice. MRictor−/− bone marrow monocytes and peritoneal macrophages expressed reduced levels of mTORC2 signaling and decreased Akt S473 phosphorylation, and they displayed significantly less proliferation than control Rictorfl/fl cells. In addition, blood monocytes and peritoneal macrophages isolated from MRictor−/− mice were significantly more sensitive to pro-apoptotic stimuli. In response to LPS, MRictor−/− macrophages exhibited the M1 phenotype with higher levels of pro-inflammatory gene expression and lower levels of Il10 gene expression than control Rictorfl/fl cells. Further suppression of LPS-stimulated Akt signaling with a low dose of an Akt inhibitor, increased inflammatory gene expression in macrophages, but genetic inactivation of Raptor reversed this rise, indicating that mTORC1 mediates this increase of inflammatory gene expression. Next, to elucidate whether mTORC2 has an impact on atherosclerosis in vivo, female and male Ldlr null mice were reconstituted with bone marrow from MRictor−/− or Rictorfl/fl mice. After 10 weeks of the Western diet, there were no differences between the recipients of the same gender in body weight, blood glucose or plasma lipid levels. However, both female and male MRictor−/− → Ldlr−/− mice developed smaller atherosclerotic lesions in the distal and proximal aorta. These lesions contained less macrophage area and more apoptosis than lesions of control Rictorfl/fl → Ldlr−/− mice. Thus, loss of Rictor and, consequently, mTORC2 significantly compromised monocyte/macrophage survival, and this markedly diminished early atherosclerosis in Ldlr−/− mice. Conclusion Our results demonstrate that mTORC2 is a key signaling regulator of macrophage survival and its depletion suppresses early atherosclerosis.
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Affiliation(s)
- Vladimir R Babaev
- Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Jiansheng Huang
- Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Lei Ding
- Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Youmin Zhang
- Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - James M May
- Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - MacRae F Linton
- Atherosclerosis Research Unit, Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
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20
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Kuck JL, Bastarache JA, Shaver CM, Fessel JP, Dikalov SI, May JM, Ware LB. Ascorbic acid attenuates endothelial permeability triggered by cell-free hemoglobin. Biochem Biophys Res Commun 2018; 495:433-437. [PMID: 29129689 PMCID: PMC5736437 DOI: 10.1016/j.bbrc.2017.11.058] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 11/08/2017] [Indexed: 01/09/2023]
Abstract
BACKGROUND Increased endothelial permeability is central to shock and organ dysfunction in sepsis but therapeutics targeted to known mediators of increased endothelial permeability have been unsuccessful in patient studies. We previously reported that cell-free hemoglobin (CFH) is elevated in the majority of patients with sepsis and is associated with organ dysfunction, poor clinical outcomes and elevated markers of oxidant injury. Others have shown that Vitamin C (ascorbate) may have endothelial protective effects in sepsis. In this study, we tested the hypothesis that high levels of CFH, as seen in the circulation of patients with sepsis, disrupt endothelial barrier integrity. METHODS Human umbilical vein endothelial cells (HUVEC) were grown to confluence and treated with CFH with or without ascorbate. Monolayer permeability was measured by Electric Cell-substrate Impedance Sensing (ECIS) or transfer of 14C-inulin. Viability was measured by trypan blue exclusion. Intracellular ascorbate was measured by HPLC. RESULTS CFH increased permeability in a dose- and time-dependent manner with 1 mg/ml of CFH increasing inulin transfer by 50% without affecting cell viability. CFH (1 mg/ml) also caused a dramatic reduction in intracellular ascorbate in the same time frame (1.4 mM without CFH, 0.23 mM 18 h after 1 mg/ml CFH, p < 0.05). Pre-treatment of HUVECs with ascorbate attenuated CFH induced permeability. CONCLUSIONS CFH increases endothelial permeability in part through depletion of intracellular ascorbate. Supplementation of ascorbate can attenuate increases in permeability mediated by CFH suggesting a possible therapeutic approach in sepsis.
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Affiliation(s)
- Jamie L. Kuck
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Julie A. Bastarache
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN
| | - Ciara M. Shaver
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Joshua P. Fessel
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN,Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - Sergey I. Dikalov
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - James M. May
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Lorraine B. Ware
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN,Corresponding author: Lorraine B. Ware, MD, Professor of Medicine and Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, 1161 21st Avenue South, T1218 MCN, Nashville, TN 37232,
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21
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Brody K, Nasypany AM, Baker RT, May JM. Analysis of Patient Outcomes Using the MyoKinesthetic System for the Treatment of Low Back Pain: A Case Series. J Chiropr Med 2017; 16:111-121. [DOI: 10.1016/j.jcm.2017.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 12/18/2016] [Accepted: 01/20/2017] [Indexed: 11/26/2022] Open
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22
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O'Day KM, Koehling EM, Vollavanh LR, Bradney D, May JM, Breedlove KM, Breedlove EL, Blair P, Nauman EA, Bowman TG. Comparison of head impact location during games and practices in Division III men's lacrosse players. Clin Biomech (Bristol, Avon) 2017; 43:23-27. [PMID: 28178579 DOI: 10.1016/j.clinbiomech.2017.01.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 01/17/2017] [Accepted: 01/18/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND Head impacts have been studied extensively in football, but little similar research has been conducted in men's lacrosse. It is important to understand the location and magnitude of head impacts during men's lacrosse to recognize the risk of head injury. METHODS Descriptive epidemiology study set on collegiate lacrosse fields. Eleven men's lacrosse players (age=20.9±1.13years, mass=83.91±9.04kg, height=179.88±5.99cm) volunteered to participate. We applied X2 sensors behind the right ear of participants for games and practices. Sensors recorded data on linear and rotational accelerations and the location of head impacts. We calculated incidence rates per 1000 exposures with 95% confidence intervals for impact locations and compared the effect of impact location on linear and rotational accelerations with Kruskal-Wallis tests. FINDINGS We verified 167 head impacts (games=112; practices=55). During games, the incidence rate was 651.16 (95% confidence interval=530.57-771.76). The high and low incidence rates for head impact locations during games were: side=410.7 (95% confidence interval=292.02-529.41) and top=26.79 (95% confidence interval=3.53-57.10). For games and practices combined, the impact locations did not significantly affect linear (χ23=6.69, P=0.08) or rotational acceleration (χ23=6.34, P=0.10). INTERPRETATION We suggest further research into the location of head impacts during games and practices. We also suggest player and coach education on head impacts as well as behavior modification in men's lacrosse athletes to reduce the incidence of impacts to the side of the head in an effort to reduce potential injury.
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23
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24
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Parker WH, Rhea EM, Qu ZC, Hecker MR, May JM. Intracellular ascorbate tightens the endothelial permeability barrier through Epac1 and the tubulin cytoskeleton. Am J Physiol Cell Physiol 2016; 311:C652-C662. [PMID: 27605450 DOI: 10.1152/ajpcell.00076.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 08/21/2016] [Indexed: 12/28/2022]
Abstract
Vitamin C, or ascorbic acid, both tightens the endothelial permeability barrier in basal cells and also prevents barrier leak induced by inflammatory agents. Barrier tightening by ascorbate in basal endothelial cells requires nitric oxide derived from activation of nitric oxide synthase. Although ascorbate did not affect cyclic AMP levels in our previous study, there remains a question of whether it might activate downstream cyclic AMP-dependent pathways. In this work, we found in both primary and immortalized cultured endothelial cells that ascorbate tightened the endothelial permeability barrier by ∼30%. In human umbilical vein endothelial cells, this occurred at what are likely physiologic intracellular ascorbate concentrations. In so doing, ascorbate decreased measures of oxidative stress and also flattened the cells to increase cell-to-cell contact. Inhibition of downstream cyclic AMP-dependent proteins via protein kinase A did not prevent ascorbate from tightening the endothelial permeability barrier, whereas inhibition of Epac1 did block the ascorbate effect. Although Epac1 was required, its mediator Rap1 was not activated. Furthermore, ascorbate acutely stabilized microtubules during depolymerization induced by colchicine and nocodazole. Over several days in culture, ascorbate also increased the amount of stable acetylated α-tubulin. Microtubule stabilization was further suggested by the finding that ascorbate increased the amount of Epac1 bound to α-tubulin. These results suggest that physiologic ascorbate concentrations tighten the endothelial permeability barrier in unstimulated cells by stabilizing microtubules in a manner downstream of cyclic AMP that might be due both to increasing nitric oxide availability and to scavenging of reactive oxygen or nitrogen species.
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Affiliation(s)
- William H Parker
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Elizabeth Meredith Rhea
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Zhi-Chao Qu
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Morgan R Hecker
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - James M May
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee; and
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Abstract
Macular edema poses a significant risk for visual loss in persons with diabetic retinopathy. It occurs when plasma constituents and fluid leak out of damaged retinal microvasculature in the area of the macula, causing loss of central vision. Apoptotic loss of pericytes surrounding capillaries is perhaps the earliest feature of diabetic vascular damage in the macula, which is also associated with dysfunction of the endothelium and loss of the otherwise very tight endothelial permeability barrier. Increased oxidative stress is a key feature of damage to both cell types, mediated by excess superoxide from glucose-induced increases in mitochondrial metabolism, as well as by activation of the receptor for advanced glycation end products (RAGE). The latter in turn activates multiple pathways, some of which lead to increased oxidative stress, such as those involving NF-ĸB, NADPH oxidase, and endothelial nitric oxide synthase. Such cellular oxidative stress is associated with low cellular and plasma ascorbic acid levels in many subjects with diabetes in poor glycemic control. Whether repletion of low ascorbate in retinal endothelium and pericytes might help to prevent diabetic macular edema is unknown. However, cell culture studies show that the vitamin prevents high-glucose and RAGE-induced apoptosis in both cell types, that it preserves nitric oxide generated by endothelial cells, and that it tightens the leaky endothelial permeability barrier. Although these findings need to be confirmed in pre-clinical animal studies, it is worth considering clinical trials to determine whether adequate ascorbate repletion is possible and whether it might help to delay or even reverse early diabetic macular edema.
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Affiliation(s)
- James M May
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-6303, United States.
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26
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Andrews D, Baker RT, May JM. Novel Posture-Based Neuromuscular Treatment for Chronic Pain and Dysfunction of the Lateral Knee - Basketball. Med Sci Sports Exerc 2016. [DOI: 10.1249/01.mss.0000485531.11544.d5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Babaev VR, Brooksbank JA, Ding L, Zhang Y, May JM, Linton MF. Abstract 129: Overexpression of P110alpha Induces Vascular Malformation in Mouse Tail, Feet and Ears. Arterioscler Thromb Vasc Biol 2016. [DOI: 10.1161/atvb.36.suppl_1.129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Phosphoinositide-3 kinases (PI3Ks) are a family of signal transduction enzymes involved in critical cellular functions such as cell growth, proliferation, differentiation, motility and survival. Class IA PI3K is composed of a heterodimer between a P110 catalytic subunit and a p85 regulatory subunit. Upregulation of P110alpha protein significantly propagates second messenger response accelerating Akt signaling. To augment Akt activity in macrophages, we generated mice with conditional myeloid lineage-specific (LysM-Cre) overexpression of P110alpha (M-P110α+). Peritoneal macrophages isolated from these mice expressed an additional band slightly different in size than P110alpha protein and had markedly increased phosphorylation of Akt. These mice also exhibited dramatic changes in blood cells including lower levels of white blood cells, B-cells and an increase in neutrophils; whereas the levels of T-cells and monocytes were not different compared to wild-type mice. Because of the defects of B-cell development, M-P110α+ mice had also splenomegaly with decreased levels of follicles. Unexpectedly, M-P110α+ mice at age of 3-4 weeks spontaneously developed a striking phenotype with massive enlargements of small vessels forming malformations in the extremities including tail, feet and ears. These vascular malformations grew very rapidly, and, at age 5-7 months, M-P110α+ mice developed severe hemorrhages from lesions on the tail and feet. The malformations appeared to be mainly venous by Doppler color ultrasonography, and histologically they represented overgrowth of venous and capillary cells that expressed endothelial markers including CD31/PECAM-1, von Willibrand factor and panendothelial cell antigen, MECA-32. These endothelial cells exhibited high levels of proliferation detected by Ki67 staining. In addition, the malformations were surrounded by high numbers of macrophages. In conclusion, M-P110α+ mice develop spontaneous capillary-venous malformations that represent a novel model of the human PIK3CA-related overgrowth spectrum. This mouse model provides a unique opportunity to develop novel therapeutic strategies to prevent capillary and venous malformations.
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Affiliation(s)
| | | | - Lei Ding
- Medicine, Vanderbilt Univ, Nashville, TN
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Babaev VR, Ding L, Zhang Y, May JM, Linton MF. Abstract 2: Loss of
Rictor
in Macrophages Suppresses Their Viability and Reduces Atherosclerosis in LDLR Null Mice. Arterioscler Thromb Vasc Biol 2016. [DOI: 10.1161/atvb.36.suppl_1.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The mammalian target of rapamycin (mTOR) is a conserved serine/threonine kinase that plays a central role in the regulation of cell viability, growth and metabolism. mTOR complex 2 (mTORC2) directly activates phosphorylation of Akt at S
473
, promoting pro-survival signaling. Rictor is an essential component of mTORC2, and genetic loss of
Rictor
inactivates the complex. To examine whether macrophage mTORC2 signaling has an impact on atherosclerosis, we transplanted male
Ldlr
null mice with bone marrow isolated from male mice with myeloid-specific
Rictor
deletion (
Rictor
-/-
, n=9) and control marrow from
Rictor
flox-flox mice (
Rictor
flox/flox
; n=10). Compared to control mice reconstituted with
Rictor
flox/flox
cells, the recipients of
Rictor
-/-
bone marrow cells exhibited dramatic changes in blood cells including lower levels of white blood cells, B-cells, T-cells and monocytes but had similar levels of neutrophils. After 8 weeks of the Western diet, both groups of recipients had similar levels of body weight, blood glucose, plasma total cholesterol and triglycerides. However,
Rictor
-/-
→
Ldlr
-/-
mice developed smaller atherosclerotic lesions in the proximal and distal aorta (46 and 40% reduction, respectively). These lesions contained less macrophage area and more apoptotic macrophages than lesions of control
Rictor
flox/flox
→
Ldlr
-/-
mice. Importantly, blood monocytes and peritoneal macrophages isolated from
Rictor
-/-
→
Ldlr
-/-
mice were more sensitive to apoptotic stimuli compared to control
Rictor
flox/flox
cells. In response to LPS,
Rictor
-/-
macrophages exhibited the M1 phenotype with high levels of pro-inflammatory gene expression. Both
Rictor
-/-
blood monocytes and macrophages had lower levels of
Il10
gene expression than
Rictor
flox/flox
cells. Thus, loss of
Rictor
and, consequently, mTORC2 in monocyte/macrophages significantly compromises their survival, and this markedly diminishes early atherosclerosis in
Ldlr
-/-
mice. Our results indicate that mTORC2 is a key signaling regulator of macrophage survival and inflammatory responses and promote atherosclerosis.
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Affiliation(s)
| | - Lei Ding
- Medicine, Vanderbilt Univ, Nashville, TN
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Babaev VR, Yeung M, Erbay E, Ding L, Zhang Y, May JM, Fazio S, Hotamisligil GS, Linton MF. Jnk1 Deficiency in Hematopoietic Cells Suppresses Macrophage Apoptosis and Increases Atherosclerosis in Low-Density Lipoprotein Receptor Null Mice. Arterioscler Thromb Vasc Biol 2016; 36:1122-31. [PMID: 27102962 DOI: 10.1161/atvbaha.116.307580] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/04/2016] [Indexed: 12/18/2022]
Abstract
OBJECTIVE The c-Jun NH2-terminal kinases (JNK) are regulated by a wide variety of cellular stresses and have been implicated in apoptotic signaling. Macrophages express 2 JNK isoforms, JNK1 and JNK2, which may have different effects on cell survival and atherosclerosis. APPROACH AND RESULTS To dissect the effect of macrophage JNK1 and JNK2 on early atherosclerosis, Ldlr(-/-) mice were reconstituted with wild-type, Jnk1(-/-), and Jnk2(-/-) hematopoietic cells and fed a high cholesterol diet. Jnk1(-/-)→Ldlr(-/-) mice have larger atherosclerotic lesions with more macrophages and fewer apoptotic cells than mice transplanted with wild-type or Jnk2(-/-) cells. Moreover, genetic ablation of JNK to a single allele (Jnk1(+/-)/Jnk2(-/-) or Jnk1(-/-)/Jnk2(+/-)) in marrow of Ldlr(-/-) recipients further increased atherosclerosis compared with Jnk1(-/-)→Ldlr(-/-) and wild-type→Ldlr(-/-) mice. In mouse macrophages, anisomycin-mediated JNK signaling antagonized Akt activity, and loss of Jnk1 gene obliterated this effect. Similarly, pharmacological inhibition of JNK1, but not JNK2, markedly reduced the antagonizing effect of JNK on Akt activity. Prolonged JNK signaling in the setting of endoplasmic reticulum stress gradually extinguished Akt and Bad activity in wild-type cells with markedly less effects in Jnk1(-/-) macrophages, which were also more resistant to apoptosis. Consequently, anisomycin increased and JNK1 inhibitors suppressed endoplasmic reticulum stress-mediated apoptosis in macrophages. We also found that genetic and pharmacological inhibition of phosphatase and tensin homolog abolished the JNK-mediated effects on Akt activity, indicating that phosphatase and tensin homolog mediates crosstalk between these pathways. CONCLUSIONS Loss of Jnk1, but not Jnk2, in macrophages protects them from apoptosis, increasing cell survival, and this accelerates early atherosclerosis.
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Affiliation(s)
- Vladimir R Babaev
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.).
| | - Michele Yeung
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.)
| | - Ebru Erbay
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.)
| | - Lei Ding
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.)
| | - Youmin Zhang
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.)
| | - James M May
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.)
| | - Sergio Fazio
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.)
| | - Gökhan S Hotamisligil
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.)
| | - MacRae F Linton
- From the Departments of Medicine (V.R.B., M.Y., L.D., Y.Z., J.M.M., M.F.L.) and Pharmacology (M.F.L.), Vanderbilt University Medical Center, Nashville, TN; Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey (E.E.); Department of Medicine, Oregon Health & Science University, Portland, OR (S.F.); and Department of Genetics & Complex Diseases & Sabri Ulker Center, Harvard School of Public Health, Boston, MA (G.S.H.).
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30
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Vergeade A, Bertram CC, Bikineyeva AT, Zackert WE, Zinkel SS, May JM, Dikalov SI, Roberts LJ, Boutaud O. Cardiolipin fatty acid remodeling regulates mitochondrial function by modifying the electron entry point in the respiratory chain. Mitochondrion 2016; 28:88-95. [PMID: 27085476 DOI: 10.1016/j.mito.2016.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 03/24/2016] [Accepted: 04/07/2016] [Indexed: 01/18/2023]
Abstract
Modifications of cardiolipin (CL) levels or compositions are associated with changes in mitochondrial function in a wide range of pathologies. We have made the discovery that acetaminophen remodels CL fatty acids composition from tetralinoleoyl to linoleoyltrioleoyl-CL, a remodeling that is associated with decreased mitochondrial respiration. Our data show that CL remodeling causes a shift in electron entry from complex II to the β-oxidation electron transfer flavoprotein quinone oxidoreductase (ETF/QOR) pathway. These data demonstrate that electron entry in the respiratory chain is regulated by CL fatty acid composition and provide proof-of-concept that pharmacological intervention can be used to modify CL composition.
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Affiliation(s)
- Aurelia Vergeade
- Department of Pharmacology, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - Clinton C Bertram
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - Alfiya T Bikineyeva
- Department of Medicine, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - William E Zackert
- Department of Pharmacology, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - Sandra S Zinkel
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States; Department of Medicine, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - James M May
- Department of Medicine, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - Sergey I Dikalov
- Department of Medicine, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - L Jackson Roberts
- Department of Pharmacology, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States; Department of Medicine, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States
| | - Olivier Boutaud
- Department of Pharmacology, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, TN 37232-6602, United States.
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31
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Babaev VR, Ding L, Zhang Y, May JM, Lin PC, Fazio S, Linton MF. Macrophage IKKα Deficiency Suppresses Akt Phosphorylation, Reduces Cell Survival, and Decreases Early Atherosclerosis. Arterioscler Thromb Vasc Biol 2016. [PMID: 26848161 PMCID: PMC4808396 DOI: 10.1161/atvbaha.115.306931,10.1161/atvbaha.115.306931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE The IκB kinase (IKK) is an enzyme complex that initiates the nuclear factor κB transcription factor cascade, which is important in regulating multiple cellular responses. IKKα is directly associated with 2 major prosurvival pathways, PI3K/Akt and nuclear factor κB, but its role in cell survival is not clear. Macrophages play critical roles in the pathogenesis of atherosclerosis, yet the impact of IKKα signaling on macrophage survival and atherogenesis remains unclear. APPROACH AND RESULTS Here, we demonstrate that genetic IKKα deficiency, as well as pharmacological inhibition of IKK, in mouse macrophages significantly reduces Akt S(473) phosphorylation, which is accompanied by suppression of mTOR complex 2 signaling. Moreover, IKKα null macrophages treated with lipotoxic palmitic acid exhibited early exhaustion of Akt signaling compared with wild-type cells. This was accompanied by a dramatic decrease in the resistance of IKKα(-/-) monocytes and macrophages to different proapoptotic stimuli compared with wild-type cells. In vivo, IKKα deficiency increased macrophage apoptosis in atherosclerotic lesions and decreased early atherosclerosis in both female and male low-density lipoprotein receptor (LDLR)(-/-) mice reconstituted with IKKα(-/-) hematopoietic cells and fed with the Western diet for 8 weeks compared with control LDLR(-/-) mice transplanted with wild-type cells. CONCLUSIONS Hematopoietic IKKα deficiency in mouse suppresses Akt signaling, compromising monocyte/macrophage survival and this decreases early atherosclerosis.
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32
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Babaev VR, Ding L, Zhang Y, May JM, Lin PC, Fazio S, Linton MF. Macrophage IKKα Deficiency Suppresses Akt Phosphorylation, Reduces Cell Survival, and Decreases Early Atherosclerosis. Arterioscler Thromb Vasc Biol 2016; 36:598-607. [PMID: 26848161 DOI: 10.1161/atvbaha.115.306931] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 01/17/2015] [Indexed: 12/12/2022]
Abstract
OBJECTIVE The IκB kinase (IKK) is an enzyme complex that initiates the nuclear factor κB transcription factor cascade, which is important in regulating multiple cellular responses. IKKα is directly associated with 2 major prosurvival pathways, PI3K/Akt and nuclear factor κB, but its role in cell survival is not clear. Macrophages play critical roles in the pathogenesis of atherosclerosis, yet the impact of IKKα signaling on macrophage survival and atherogenesis remains unclear. APPROACH AND RESULTS Here, we demonstrate that genetic IKKα deficiency, as well as pharmacological inhibition of IKK, in mouse macrophages significantly reduces Akt S(473) phosphorylation, which is accompanied by suppression of mTOR complex 2 signaling. Moreover, IKKα null macrophages treated with lipotoxic palmitic acid exhibited early exhaustion of Akt signaling compared with wild-type cells. This was accompanied by a dramatic decrease in the resistance of IKKα(-/-) monocytes and macrophages to different proapoptotic stimuli compared with wild-type cells. In vivo, IKKα deficiency increased macrophage apoptosis in atherosclerotic lesions and decreased early atherosclerosis in both female and male low-density lipoprotein receptor (LDLR)(-/-) mice reconstituted with IKKα(-/-) hematopoietic cells and fed with the Western diet for 8 weeks compared with control LDLR(-/-) mice transplanted with wild-type cells. CONCLUSIONS Hematopoietic IKKα deficiency in mouse suppresses Akt signaling, compromising monocyte/macrophage survival and this decreases early atherosclerosis.
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Affiliation(s)
- Vladimir R Babaev
- From the Atherosclerosis Research Unit, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., M.R.F.L.) and Pharmacology (M.R.F.L.), Vanderbilt University Medical Center, Nashville, TN; Center for Cancer Research, National Cancer Institute, Frederick, MD (P.C.L.); and Department of Medicine, Center of Preventive Cardiology, Oregon Health & Science University, Portland, OR (S.F.).
| | - Lei Ding
- From the Atherosclerosis Research Unit, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., M.R.F.L.) and Pharmacology (M.R.F.L.), Vanderbilt University Medical Center, Nashville, TN; Center for Cancer Research, National Cancer Institute, Frederick, MD (P.C.L.); and Department of Medicine, Center of Preventive Cardiology, Oregon Health & Science University, Portland, OR (S.F.)
| | - Youmin Zhang
- From the Atherosclerosis Research Unit, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., M.R.F.L.) and Pharmacology (M.R.F.L.), Vanderbilt University Medical Center, Nashville, TN; Center for Cancer Research, National Cancer Institute, Frederick, MD (P.C.L.); and Department of Medicine, Center of Preventive Cardiology, Oregon Health & Science University, Portland, OR (S.F.)
| | - James M May
- From the Atherosclerosis Research Unit, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., M.R.F.L.) and Pharmacology (M.R.F.L.), Vanderbilt University Medical Center, Nashville, TN; Center for Cancer Research, National Cancer Institute, Frederick, MD (P.C.L.); and Department of Medicine, Center of Preventive Cardiology, Oregon Health & Science University, Portland, OR (S.F.)
| | - P Charles Lin
- From the Atherosclerosis Research Unit, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., M.R.F.L.) and Pharmacology (M.R.F.L.), Vanderbilt University Medical Center, Nashville, TN; Center for Cancer Research, National Cancer Institute, Frederick, MD (P.C.L.); and Department of Medicine, Center of Preventive Cardiology, Oregon Health & Science University, Portland, OR (S.F.)
| | - Sergio Fazio
- From the Atherosclerosis Research Unit, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., M.R.F.L.) and Pharmacology (M.R.F.L.), Vanderbilt University Medical Center, Nashville, TN; Center for Cancer Research, National Cancer Institute, Frederick, MD (P.C.L.); and Department of Medicine, Center of Preventive Cardiology, Oregon Health & Science University, Portland, OR (S.F.)
| | - MacRae F Linton
- From the Atherosclerosis Research Unit, Department of Medicine (V.R.B., L.D., Y.Z., J.M.M., M.R.F.L.) and Pharmacology (M.R.F.L.), Vanderbilt University Medical Center, Nashville, TN; Center for Cancer Research, National Cancer Institute, Frederick, MD (P.C.L.); and Department of Medicine, Center of Preventive Cardiology, Oregon Health & Science University, Portland, OR (S.F.)
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33
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Ulker E, Parker WH, Raj A, Qu ZC, May JM. Ascorbic acid prevents VEGF-induced increases in endothelial barrier permeability. Mol Cell Biochem 2015; 412:73-9. [PMID: 26590088 DOI: 10.1007/s11010-015-2609-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 11/14/2015] [Indexed: 02/07/2023]
Abstract
Vascular endothelial growth factor (VEGF) increases endothelial barrier permeability, an effect that may contribute to macular edema in diabetic retinopathy. Since vitamin C, or ascorbic acid, can tighten the endothelial permeability barrier, we examined whether it could prevent the increase in permeability due to VEGF in human umbilical vein endothelial cells (HUVECs). As previously observed, VEGF increased HUVEC permeability to radiolabeled inulin within 60 min in a concentration-dependent manner. Loading the cells with increasing concentrations of ascorbate progressively prevented the leakage caused by 100 ng/ml VEGF, with a significant inhibition at 13 µM and complete inhibition at 50 µM. Loading cells with 100 µM ascorbate also decreased the basal generation of reactive oxygen species and prevented the increase caused by both 100 ng/ml VEGF. VEGF treatment decreased intracellular ascorbate by 25%, thus linking ascorbate oxidation to its prevention of VEGF-induced barrier leakage. The latter was blocked by treating the cells with 60 µM L-NAME (but not D-NAME) as well as by 30 µM sepiapterin, a precursor of tetrahydrobiopterin that is required for proper function of endothelial nitric oxide synthase (eNOS). These findings suggest that VEGF-induced barrier leakage uncouples eNOS. Ascorbate inhibition of the VEGF effect could thus be due either to scavenging superoxide or to peroxynitrite generated by the uncoupled eNOS, or more likely to its ability to recycle tetrahydrobiopterin, thus avoiding enzyme uncoupling in the first place. Ascorbate prevention of VEGF-induced increases in endothelial permeability opens the possibility that its repletion could benefit diabetic macular edema.
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Affiliation(s)
- Esad Ulker
- Department of Medicine, Vanderbilt University School of Medicine, 7465 Medical Research Building IV, Nashville, TN, 37232-0475, USA
| | - William H Parker
- Department of Medicine, Vanderbilt University School of Medicine, 7465 Medical Research Building IV, Nashville, TN, 37232-0475, USA
| | - Amita Raj
- Department of Medicine, Vanderbilt University School of Medicine, 7465 Medical Research Building IV, Nashville, TN, 37232-0475, USA
| | - Zhi-chao Qu
- Department of Medicine, Vanderbilt University School of Medicine, 7465 Medical Research Building IV, Nashville, TN, 37232-0475, USA
| | - James M May
- Department of Medicine, Vanderbilt University School of Medicine, 7465 Medical Research Building IV, Nashville, TN, 37232-0475, USA.
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35
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Pierce MR, Raj A, Betke KM, Zeidan LN, Matthies HJG, May JM. Sodium-dependent vitamin C transporter-2 mediates vitamin C transport at the cortical nerve terminal. J Neurosci Res 2015; 93:1881-90. [PMID: 26366722 DOI: 10.1002/jnr.23669] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 08/04/2015] [Accepted: 08/31/2015] [Indexed: 11/09/2022]
Abstract
It has been shown that vitamin C (VC) is transported at synaptic boutons, but how this occurs has not been elucidated. This study investigates the role of the sodium-dependent vitamin C transporter-2 (SVCT2) in transporting VC at the cortical nerve terminal. Immunostaining of cultured mouse superior cervical ganglion cells showed the SVCT2 to be expressed in presynaptic boutons, colocalizing with the vesicular monoamine transporter-2 and the norepinephrine transporter. Immunoblotting of enriched cortical synaptosomes demonstrated that the SVCT2 was enriched in presynaptic fractions, confirming a predominantly presynaptic location. In crude synaptosomes, known inhibitors of SVCT2 inhibited uptake of VC. Furthermore, the kinetic features of VC uptake were consistent with SVCT2-mediated function. VC was also found to efflux from synaptosomes by a mechanism not involving the SVCT2. Indeed, VC efflux was substantially offset by reuptake of VC on the SVCT2. The presence and function of the SVCT2 at the presynaptic nerve terminal suggest that it is the transporter responsible for recovery of VC released into the synaptic cleft.
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Affiliation(s)
- Marquicia R Pierce
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Amita Raj
- Department of Neuroscience, Vanderbilt University, Nashville, Tennessee
| | - Katherine M Betke
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - L Nora Zeidan
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Heinrich J G Matthies
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - James M May
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
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36
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May JM, Kyriacou PA, Petros AJ. Pilot investigation of anterior fontanelle photoplethysmographic signals and their suitability in estimating arterial oxygen saturation. Annu Int Conf IEEE Eng Med Biol Soc 2015; 2013:2656-9. [PMID: 24110273 DOI: 10.1109/embc.2013.6610086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
There is a need for more reliable, non-invasive and alternative measurement sites for the monitoring of arterial blood oxygen saturation in critically ill newborns at times of peripheral compromise. A pilot investigation on 14 Intensive Care Unit (ICU) newborns was conducted utilizing custom-made reflectance photoplethysmographic (PPG) sensors placed at the fontanelle and foot. The results suggest that the fontanelle is sensitive to changes in saturation, where saturation values obtained from the custom sensor were compared against commercial pulse oximeter values and results from a blood gas analyzer, however careful placement of the sensor at the fontanelle is an issue that needs further investigation.
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37
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Brown JA, Pensabene V, Markov DA, Allwardt V, Neely MD, Shi M, Britt CM, Hoilett OS, Yang Q, Brewer BM, Samson PC, McCawley LJ, May JM, Webb DJ, Li D, Bowman AB, Reiserer RS, Wikswo JP. Recreating blood-brain barrier physiology and structure on chip: A novel neurovascular microfluidic bioreactor. Biomicrofluidics 2015; 9:054124. [PMID: 26576206 PMCID: PMC4627929 DOI: 10.1063/1.4934713] [Citation(s) in RCA: 268] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 10/10/2015] [Indexed: 05/04/2023]
Abstract
The blood-brain barrier (BBB) is a critical structure that serves as the gatekeeper between the central nervous system and the rest of the body. It is the responsibility of the BBB to facilitate the entry of required nutrients into the brain and to exclude potentially harmful compounds; however, this complex structure has remained difficult to model faithfully in vitro. Accurate in vitro models are necessary for understanding how the BBB forms and functions, as well as for evaluating drug and toxin penetration across the barrier. Many previous models have failed to support all the cell types involved in the BBB formation and/or lacked the flow-created shear forces needed for mature tight junction formation. To address these issues and to help establish a more faithful in vitro model of the BBB, we have designed and fabricated a microfluidic device that is comprised of both a vascular chamber and a brain chamber separated by a porous membrane. This design allows for cell-to-cell communication between endothelial cells, astrocytes, and pericytes and independent perfusion of both compartments separated by the membrane. This NeuroVascular Unit (NVU) represents approximately one-millionth of the human brain, and hence, has sufficient cell mass to support a breadth of analytical measurements. The NVU has been validated with both fluorescein isothiocyanate (FITC)-dextran diffusion and transendothelial electrical resistance. The NVU has enabled in vitro modeling of the BBB using all human cell types and sampling effluent from both sides of the barrier.
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Affiliation(s)
| | - Virginia Pensabene
- Department of Biomedical Engineering, Vanderbilt University , Nashville, Tennessee 37235, USA
| | | | - Vanessa Allwardt
- Department of Physics and Astronomy, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - M Diana Neely
- Department of Neurology, Vanderbilt Kennedy Center, Vanderbilt Brain Institute, Vanderbilt Center in Molecular Toxicology, Vanderbilt University , Nashville, Tennessee 37232, USA
| | - Mingjian Shi
- Department of Biological Sciences, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - Clayton M Britt
- Department of Physics and Astronomy, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - Orlando S Hoilett
- Department of Physics and Astronomy, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - Qing Yang
- Department of Physics and Astronomy, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - Bryson M Brewer
- Department of Mechanical Engineering, Vanderbilt University , Nashville, Tennessee 37235, USA
| | | | | | - James M May
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - Donna J Webb
- Department of Biological Sciences, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - Deyu Li
- Department of Mechanical Engineering, Vanderbilt University , Nashville, Tennessee 37235, USA
| | - Aaron B Bowman
- Department of Neurology, Vanderbilt Kennedy Center, Vanderbilt Brain Institute, Vanderbilt Center in Molecular Toxicology, Vanderbilt University , Nashville, Tennessee 37232, USA
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38
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Abstract
Microvascular pericytes take up ascorbic acid on the ascorbate transporter SVCT2. Intracellular ascorbate then protects the cells against apoptosis induced by culture at diabetic glucose concentrations. To investigate whether pericytes might also provide ascorbate to the underlying endothelial cells, we studied ascorbate efflux from human pericytes. When loaded with ascorbate to intracellular concentrations of 0.8-1.0 mM, almost two-thirds of intracellular ascorbate effluxed from the cells over 2 H. This efflux was opposed by ascorbate re-uptake from the medium, since preventing re-uptake by destroying extracellular ascorbate with ascorbate oxidase increased ascorbate loss even further. Ascorbate re-uptake occurred on the SVCT2, since its blockade by replacing medium sodium with choline, by the SVCT2 inhibitor sulfinpyrazone, or by extracellular ascorbate accelerated ascorbate loss from the cells. This was supported by finding that net efflux of radiolabeled ascorbate was increased by unlabeled extracellular ascorbate with a half-maximal effect in the range of the high affinity Km of the SVCT2. Intracellular ascorbate did not inhibit its efflux. To assess the mechanism of ascorbate efflux, known inhibitors of volume-regulated anion channels (VRACs) were tested. These potently inhibited ascorbate transport into cells on the SVCT2, but not its efflux. An exception was the anion transport inhibitor DIDS, which, despite inhibition of ascorbate uptake, also inhibited net efflux at 25-50 µM. These results suggest that ascorbate efflux from vascular pericytes occurs on a DIDS-inhibitable transporter or channel different from VRACs. Further, ascorbate efflux is opposed by re-uptake of ascorbate on the SVCT2, providing a potential regulatory mechanism.
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Affiliation(s)
- James M. May
- To whom correspondence should be addressed: Dr. James May, 7465 Medical Research Building IV, Vanderbilt University School of Medicine, Nashville, TN 37232-0475. Tel. (615) 936-1653; Fax: (615) 936-1667.
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Parker WH, Qu ZC, May JM. Intracellular Ascorbate Prevents Endothelial Barrier Permeabilization by Thrombin. J Biol Chem 2015; 290:21486-97. [PMID: 26152729 DOI: 10.1074/jbc.m115.662098] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Indexed: 12/11/2022] Open
Abstract
Intracellular ascorbate (vitamin C) has previously been shown to tighten the endothelial barrier and maintain barrier integrity during acute inflammation in vitro. However, the downstream effectors of ascorbate in the regulation of endothelial permeability remain unclear. In this study, we evaluated ascorbate as a mediator of thrombin-induced barrier permeabilization in human umbilical vein endothelial cells and their immortalized hybridoma line, EA.hy926. We found that the vitamin fully prevented increased permeability to the polysaccharide inulin by thrombin in a dose-dependent manner, and it took effect both before and after subjection to thrombin. Thrombin exposure consumed intracellular ascorbate but not the endogenous antioxidant GSH. Likewise, the antioxidants dithiothreitol and tempol did not reverse permeabilization. We identified a novel role for ascorbate in preserving cAMP during thrombin stimulation, resulting in two downstream effects. First, ascorbate maintained the cortical actin cytoskeleton in a Rap1- and Rac1-dependent manner, thus preserving stable adherens junctions between adjacent cells. Second, ascorbate prevented actin polymerization and formation of stress fibers by reducing the activation of RhoA and phosphorylation of myosin light chain. Although ascorbate and thrombin both required calcium for their respective effects, ascorbate did not prevent thrombin permeabilization by obstructing calcium influx. However, preservation of cAMP by ascorbate was found to depend on both the production of nitric oxide by endothelial nitric-oxide synthase, which ascorbate is known to activate, and the subsequent generation cGMP by guanylate cyclase. Together, these data implicate ascorbate in the prevention of inflammatory endothelial barrier permeabilization and explain the underlying signaling mechanism.
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Affiliation(s)
- William H Parker
- From the Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6303
| | - Zhi-chao Qu
- From the Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6303
| | - James M May
- From the Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6303
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Loutsch RA, Baker RT, May JM, Nasypany AM. REACTIVE NEUROMUSCULAR TRAINING RESULTS IN IMMEDIATE AND LONG TERM IMPROVEMENTS IN MEASURES OF HAMSTRING FLEXIBILITY: A CASE REPORT. Int J Sports Phys Ther 2015; 10:371-377. [PMID: 26075153 PMCID: PMC4458925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023] Open
Abstract
BACKGROUND AND PURPOSE Hamstring tightness is a common complaint among active individuals and patients are traditionally classified with tight hamstrings based on commonly accepted clinical exams including the active knee extension, active straight leg raise, and passive straight leg raise tests. Apparent hamstring tightness is a condition that is present in patients who have the perception of hamstring tightness and are classified with a tissue extensibility dysfunction but demonstrate immediate gains in hamstring range of motion following an intervention that does not address a tissue length dysfunction. Reactive neuromuscular training can be used as part of the evaluative process used to classify and treat patients with apparent hamstring tightness. The purpose of this case report was to identify, treat, and report the outcomes experienced when using a reactive neuromuscular training technique on a patient who was classified with hamstring inflexibility based on traditional testing methods. CASE DESCRIPTION A 20 year-old female softball player presented with a chief complaint of hamstring tightness of more than four years duration. The patient tested positive for hamstring inflexibility based on traditional testing methods. The patient was then treated using a reactive neuromuscular training technique in which the patient resisted a manual anterior to posterior force at the abdomen, sternum and across the hips while simultaneously bending forward at the hips in an attempt to touch her toes. OUTCOMES Following one reactive neuromuscular training treatment session the patient tested negative for hamstring inflexibility based on traditional testing methods and maintained those results at a five-week follow-up appointment. DISCUSSION The subject in this case report demonstrated the effectiveness of reactive neuromuscular training in identifying and treating apparent hamstring tightness. Based on these findings, clinicians should consider using reactive neuromuscular training to properly classify and treat patients with a chief complaint of hamstring "tightness." LEVEL OF EVIDENCE 4 (single case report).
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Babaev VR, Ding L, Zhang Y, May JM, Linton MF. Abstract 549: Loss of Macrophage Akt2/Akt3 or Akt1/Akt2 Decreases Cell Survival and Suppresses Early Atherosclerosis in Ldlr Null Mice. Arterioscler Thromb Vasc Biol 2015. [DOI: 10.1161/atvb.35.suppl_1.549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Akt is a serine/threonine-specific protein kinase that plays a key role in multiple cellular processes including glucose metabolism and cell survival. Macrophages express three Akt isoforms, Akt1, Akt2 and Akt3 which have been ascribed a number of isoform specific effects but may also be functionally redundant in terms of Akt signaling. Here we hypothesize that dramatic reduction of Akt content with loss of two isoforms will suppress Akt signaling in macrophages, reducing their survival and modulating the development of atherosclerosis. To test this hypothesis, we generated mice with combined deficiency Akt2/Akt3 in hematopoietic cells. Peritoneal macrophages isolated from these mice preserved a similar level of Akt phosphorylation when treated with insulin but exhibited a dramatic increase in apoptosis in response to several different factors that induce ER stress compared to WT or single Akt2 or Akt3 knockout macrophages. Male LDLR null mice reconstituted with double Akt2/Akt3 knockout hematopoietic cells and fed the Western diet for 8 weeks developed smaller (57.6 % reduction) atherosclerotic lesions with more apoptotic macrophages in the proximal aorta than control WT→LDLR
-/-
mice, in the absence of changes in plasma lipid levels. Thus, loss of Akt2/Akt3 in macrophages increases their sensitivity to apoptosis and decreases atherosclerosis. Next, we generated mice with combined deficiency of Akt1/Akt2 in hematopoietic cells. Again, loss of a single Akt1 or Akt2 isoform in macrophages had no impact on cell apoptosis, whereas combined Akt1/Akt2 deficiency did not change Akt phosphorylation but markedly compromised their sensitivity to different apoptotic stimuli. Furthermore, male and female LDLR
-/-
mice transplanted with Akt1/Akt2 knockout hematopoietic cells had significantly smaller atherosclerotic lesions with increased macrophage apoptosis than control WT→LDLR
-/-
mice. Taken together these data indicate that a dramatic reduction of Akt protein in macrophages with loss of either of the Akt1/Akt2 or Akt2/Akt3 pairs of isoforms significantly compromises cell survival and this diminishes early atherosclerosis.
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Affiliation(s)
| | - Lei Ding
- Medicine, Vanderbilt Univ, Nashville, TN
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Abstract
Intracellular vitamin C, or ascorbic acid, has been shown to prevent the apoptosis of cultured vascular pericytes under simulated diabetic conditions. We sought to determine the mechanism by which ascorbate is transported into pericytes prior to exerting this protective effect. Measuring intracellular ascorbate, we found that pericytes display a linear uptake over 30 min and an apparent transport Km of 21 μM, both of which are consistent with activity of the Sodium-dependent Vitamin C Transporter 2 (SVCT2). Uptake of both radiolabeled and unlabeled ascorbate was prevented by inhibiting SVCT2 activity, but not by inhibiting the activity of GLUT-type glucose transporters, which import dehydroascorbate to also generate intracellular ascorbate. Likewise, uptake of dehydroascorbate was prevented with the inhibition of GLUTs, but not by inhibiting the SVCT2, indicating substrate specificity of both transporters. Finally, presence of the SVCT2 in pericytes was confirmed by western blot analysis, and immunocytochemistry was used to localize it to the plasma membrane and intracellular sites. Together, these data clarify previous inconsistencies in the literature, implicate SVCT2 as the pericyte ascorbate transporter, and show that pericytes are capable of concentrating intracellular ascorbate against a gradient in an energy- and sodium-dependent fashion.
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Affiliation(s)
- William H Parker
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-0475, USA
| | - Zhi-Chao Qu
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-0475, USA
| | - James M May
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-0475, USA.
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May JM, Hickey M, Triantis I, Palazidou E, Kyriacou PA. Optical analysis of lithium carbonate: towards the development of a portable lithium blood level analyzer for bipolar disorder patients. Annu Int Conf IEEE Eng Med Biol Soc 2015; 2014:2077-80. [PMID: 25570393 DOI: 10.1109/embc.2014.6944025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lithium medication is the gold standard of treatment in Bipolar Disorder patients, preventing and reducing mood swings and suicidality. However, despite its effectiveness, it is a potentially hazardous drug requiring regular monitoring of blood levels to ensure toxic levels are not reached. This paper describes the first steps towards developing a new portable device that can be used by Bipolar Disorder patients to facilitate the analysis of lithium blood levels at home. Solutions of lithium carbonate have been optically fingerprinted using a high-end spectrophotometer. Preliminary measurements indicate that while the visible to near infrared region of the absorption spectra fall heavily within the water band, measurements in the Ultraviolet region show a strong distinction between different lithium concentrations. The optical spectra of Lithium in the 220 nm to 230 nm region demonstrated the ability to differentiate between concentrations representing those found in patients.
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, McGrath JC, Catterall WA, Spedding M, Peters JA, Harmar AJ, Abul-Hasn N, Anderson CM, Anderson CMH, Araiksinen MS, Arita M, Arthofer E, Barker EL, Barratt C, Barnes NM, Bathgate R, Beart PM, Belelli D, Bennett AJ, Birdsall NJM, Boison D, Bonner TI, Brailsford L, Bröer S, Brown P, Calo G, Carter WG, Catterall WA, Chan SLF, Chao MV, Chiang N, Christopoulos A, Chun JJ, Cidlowski J, Clapham DE, Cockcroft S, Connor MA, Cox HM, Cuthbert A, Dautzenberg FM, Davenport AP, Dawson PA, Dent G, Dijksterhuis JP, Dollery CT, Dolphin AC, Donowitz M, Dubocovich ML, Eiden L, Eidne K, Evans BA, Fabbro D, Fahlke C, Farndale R, Fitzgerald GA, Fong TM, Fowler CJ, Fry JR, Funk CD, Futerman AH, Ganapathy V, Gaisnier B, Gershengorn MA, Goldin A, Goldman ID, Gundlach AL, Hagenbuch B, Hales TG, Hammond JR, Hamon M, Hancox JC, Hauger RL, Hay DL, Hobbs AJ, Hollenberg MD, Holliday ND, Hoyer D, Hynes NA, Inui KI, Ishii S, Jacobson KA, Jarvis GE, Jarvis MF, Jensen R, Jones CE, Jones RL, Kaibuchi K, Kanai Y, Kennedy C, Kerr ID, Khan AA, Klienz MJ, Kukkonen JP, Lapoint JY, Leurs R, Lingueglia E, Lippiat J, Lolait SJ, Lummis SCR, Lynch JW, MacEwan D, Maguire JJ, Marshall IL, May JM, McArdle CA, McGrath JC, Michel MC, Millar NS, Miller LJ, Mitolo V, Monk PN, Moore PK, Moorhouse AJ, Mouillac B, Murphy PM, Neubig RR, Neumaier J, Niesler B, Obaidat A, Offermanns S, Ohlstein E, Panaro MA, Parsons S, Pwrtwee RG, Petersen J, Pin JP, Poyner DR, Prigent S, Prossnitz ER, Pyne NJ, Pyne S, Quigley JG, Ramachandran R, Richelson EL, Roberts RE, Roskoski R, Ross RA, Roth M, Rudnick G, Ryan RM, Said SI, Schild L, Sanger GJ, Scholich K, Schousboe A, Schulte G, Schulz S, Serhan CN, Sexton PM, Sibley DR, Siegel JM, Singh G, Sitsapesan R, Smart TG, Smith DM, Soga T, Stahl A, Stewart G, Stoddart LA, Summers RJ, Thorens B, Thwaites DT, Toll L, Traynor JR, Usdin TB, Vandenberg RJ, Villalon C, Vore M, Waldman SA, Ward DT, Willars GB, Wonnacott SJ, Wright E, Ye RD, Yonezawa A, Zimmermann M. The Concise Guide to PHARMACOLOGY 2013/14: overview. Br J Pharmacol 2014; 170:1449-58. [PMID: 24528237 DOI: 10.1111/bph.12444] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties from the IUPHAR database. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. This compilation of the major pharmacological targets is divided into seven areas of focus: G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors & Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and GRAC and provides a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen P H Alexander
- School of Life Sciences, University of Nottingham Medical School, Nottingham, NG7 2UH, UK
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Babaev VR, Hebron KE, Wiese CB, Toth CL, Ding L, Zhang Y, May JM, Fazio S, Vickers KC, Linton MF. Macrophage deficiency of Akt2 reduces atherosclerosis in Ldlr null mice. J Lipid Res 2014; 55:2296-308. [PMID: 25240046 PMCID: PMC4617132 DOI: 10.1194/jlr.m050633] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Macrophages play crucial roles in the formation of atherosclerotic lesions. Akt, a serine/threonine protein kinase B, is vital for cell proliferation, migration, and survival. Macrophages express three Akt isoforms, Akt1, Akt2, and Akt3, but the roles of Akt1 and Akt2 in atherosclerosis in vivo remain unclear. To dissect the impact of macrophage Akt1 and Akt2 on early atherosclerosis, we generated mice with hematopoietic deficiency of Akt1 or Akt2. After 8 weeks on Western diet, Ldlr−/− mice reconstituted with Akt1−/− fetal liver cells (Akt1−/−→Ldlr−/−) had similar atherosclerotic lesion areas compared with control mice transplanted with WT cells (WT→Ldlr−/−). In contrast, Akt2−/−→Ldlr−/− mice had dramatically reduced atherosclerotic lesions compared with WT→Ldlr−/− mice of both genders. Similarly, in the setting of advanced atherosclerotic lesions, Akt2−/−→Ldlr−/− mice had smaller aortic lesions compared with WT→Ldlr−/− and Akt1−/−→Ldlr−/− mice. Importantly, Akt2−/−→Ldlr−/− mice had reduced numbers of proinflammatory blood monocytes expressing Ly-6Chi and chemokine C-C motif receptor 2. Peritoneal macrophages isolated from Akt2−/− mice were skewed toward an M2 phenotype and showed decreased expression of proinflammatory genes and reduced cell migration. Our data demonstrate that loss of Akt2 suppresses the ability of macrophages to undergo M1 polarization reducing both early and advanced atherosclerosis.
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Affiliation(s)
- Vladimir R Babaev
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Katie E Hebron
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Carrie B Wiese
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Cynthia L Toth
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Lei Ding
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Youmin Zhang
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232
| | - James M May
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Sergio Fazio
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232 Department of Pathology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Kasey C Vickers
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232 Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232
| | - MacRae F Linton
- Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232 Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232
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Abstract
Photoplethysmography (PPG) signals have been investigated at a new anatomical site, the anterior fontanelle (ANTF), on the hypothesis that blood supply at this location is preferentially preserved during cases of poor peripheral circulation which might cause the commercial pulse oximeters to fail to estimate accurately arterial blood oxygen saturation (SpO2). Two custom built reflectance PPG sensors have been developed, one for placement on the fontanelle and one on the periphery (foot). A PPG processing system and software were also developed to process the raw PPG signals and to estimate SpO2. A pilot study on sixteen babies, (9 male, 7 female) with a median age of 15.5 d (interquartile range = 46.8 d) and a median weight of 3.15 kg (SD = 0.93 kg), on a neonatal intensive care unit (NICU) has been carried out. PPG signals from the ANTF were of good quality and high signal-to-noise ratio. The amplitudes of the ANTF PPGs were found to be sensitive to changes in amplitude when amplitudes were observed at the reference PPG site. Bland-Altman analysis of the gold standard blood gas analysis reveals that all three sensors are inaccurate at SaO2 < 85-90 %, but the ANTF sensor shows better mean difference than the commercial device.
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Affiliation(s)
- J M May
- Biomedical Engineering Research Group, School of Engineering and Mathematical Sciences, City University London, London, EC1V 0HB, UK
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Meredith ME, Qu ZC, May JM. Ascorbate reverses high glucose- and RAGE-induced leak of the endothelial permeability barrier. Biochem Biophys Res Commun 2014; 445:30-5. [PMID: 24472555 DOI: 10.1016/j.bbrc.2014.01.078] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 01/20/2014] [Indexed: 02/07/2023]
Abstract
High glucose concentrations due to diabetes increase leakage of plasma constituents across the endothelial permeability barrier. We sought to determine whether vitamin C, or ascorbic acid (ascorbate), could reverse such high glucose-induced increases in endothelial barrier permeability. Human umbilical vein endothelial cells and two brain endothelial cell lines cultured at 25 mM glucose showed increases in endothelial barrier permeability to radiolabeled inulin compared to cells cultured at 5mM glucose. Acute loading of the cells for 30-60 min with ascorbate before the permeability assay prevented the high glucose-induced increase in permeability and decreased basal permeability at 5mM glucose. High glucose-induced barrier leakage was mediated largely by activation of the receptor for advanced glycation end products (RAGE), since it was prevented by RAGE blockade and mimicked by RAGE ligands. Intracellular ascorbate completely prevented RAGE ligand-induced increases in barrier permeability. The high glucose-induced increase in endothelial barrier permeability was also acutely decreased by several cell-penetrant antioxidants, suggesting that at least part of the ascorbate effect could be due to its ability to act as an antioxidant.
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Affiliation(s)
- M Elizabeth Meredith
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0475, United States
| | - Zhi-Chao Qu
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-0475, United States
| | - James M May
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0475, United States; Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-0475, United States.
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Manning J, Mitchell B, Appadurai DA, Shakya A, Pierce LJ, Wang H, Nganga V, Swanson PC, May JM, Tantin D, Spangrude GJ. Vitamin C promotes maturation of T-cells. Antioxid Redox Signal 2013; 19:2054-67. [PMID: 23249337 PMCID: PMC3869442 DOI: 10.1089/ars.2012.4988] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
AIMS Vitamin C (ascorbic acid) is thought to enhance immune function, but the mechanisms involved are obscure. We utilized an in vitro model of T-cell maturation to evaluate the role of ascorbic acid in lymphocyte development. RESULTS Ascorbic acid was essential for the developmental progression of mouse bone marrow-derived progenitor cells to functional T-lymphocytes in vitro and also played a role in vivo. Ascorbate-mediated enhancement of T-cell development was lymphoid cell-intrinsic and independent of T-cell receptor (TCR) rearrangement. Analysis of TCR rearrangements demonstrated that ascorbic acid enhanced the selection of functional TCRαβ after the stage of β-selection. Genes encoding the coreceptor CD8 as well as the kinase ZAP70 were upregulated by ascorbic acid. Pharmacologic inhibition of methylation marks on DNA and histones enhanced ascorbate-mediated differentiation, suggesting an epigenetic mechanism of Cd8 gene regulation via active demethylation by ascorbate-dependent Fe(2+) and 2-oxoglutarate-dependent dioxygenases. INNOVATION We speculate that one aspect of gene regulation mediated by ascorbate occurs at the level of chromatin demethylation, mediated by Jumonji C (JmjC) domain enzymes that are known to be reliant upon ascorbate as a cofactor. JmjC domain enzymes are also known to regulate transcription factor activity. These two mechanisms are likely to play key roles in the modulation of immune development and function by ascorbic acid. CONCLUSION Our results provide strong experimental evidence supporting a role for ascorbic acid in T-cell maturation as well as insight into the mechanism of ascorbate-mediated enhancement of immune function.
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Affiliation(s)
- Jared Manning
- 1 Division of Hematology, Department of Medicine, University of Utah , Salt Lake City, Utah
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Abstract
SIGNIFICANCE Vitamin C, or ascorbic acid, has long been known to participate in several important functions in the vascular bed in support of endothelial cells. These functions include increasing the synthesis and deposition of type IV collagen in the basement membrane, stimulating endothelial proliferation, inhibiting apoptosis, scavenging radical species, and sparing endothelial cell-derived nitric oxide to help modulate blood flow. Although ascorbate may not be able to reverse inflammatory vascular diseases such as atherosclerosis, it may well play a role in preventing the endothelial dysfunction that is the earliest sign of many such diseases. RECENT ADVANCES Beyond simply preventing scurvy, evidence is mounting that ascorbate is required for optimal function of many dioxygenase enzymes in addition to those involved in collagen synthesis. Several of these enzymes regulate the transcription of proteins involved in endothelial function, proliferation, and survival, including hypoxia-inducible factor-1α and histone and DNA demethylases. More recently, ascorbate has been found to acutely tighten the endothelial permeability barrier and, thus, may modulate access of ascorbate and other molecules into tissues and organs. CRITICAL ISSUES The issue of the optimal cellular content of ascorbate remains unresolved, but it appears that low millimolar ascorbate concentrations are normal in most animal tissues, in human leukocytes, and probably in the endothelium. Although there may be little benefit of increasing near maximal cellular ascorbate concentrations in normal people, many diseases and conditions have either systemic or localized cellular ascorbate deficiency as a cause for endothelial dysfunction, including early atherosclerosis, sepsis, smoking, and diabetes. FUTURE DIRECTIONS A key focus for future studies of ascorbate and the vascular endothelium will likely be to determine the mechanisms and clinical relevance of ascorbate effects on endothelial function, permeability, and survival in diseases that cause endothelial dysfunction.
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Affiliation(s)
- James M May
- Department of Medicine, Vanderbilt University School of Medicine , Nashville, Tennessee
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Kyriacou PA, May JM, Petros AJ. Esophageal SpO2 measurements from a pediatric burns-patient: a case study. Annu Int Conf IEEE Eng Med Biol Soc 2013; 2013:1732-1735. [PMID: 24110041 DOI: 10.1109/embc.2013.6609854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Pulse oximetry is being used in everyday clinical practice in anesthesia utilizing peripheral saturation sensors. However, it may be unreliable in certain clinical situations such as peripheral hypoperfusion. Similar situations occur in burns patients and more importantly burns to extremities which limit the sites available for measurement of peripheral oxygen saturation (SpO2). To overcome these limitations, the esophagus has been investigated as an alternative measurement site, as perfusion may be preferentially preserved centrally. A miniaturized reflectance esophageal saturation (SpO2 probe has been constructed utilizing infrared and red photodiodes and a photodetector. Our case study was aimed at evaluating the reliability of esophageal pulse oximetry in a major burns infant. Measurable photoplethysmographic (PPG) traces and SpO2 values were obtained in the neonatal esophagus. It was found that the esophageal pulse oximeter results were in good agreement with oxygen saturation measurements obtained by a commercial ear lobe pulse oximeter. This study suggests that the esophagus can be used as an alternative site for monitoring arterial blood oxygen saturation by pulse oximetry in burned infants.
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