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Westwood J, Mayhook-Walker I, Simpkins C, Darby-Smith A, Morris D, Normando E. Retinal Vascular Changes in Response to Hypoxia: A High-Altitude Expedition Study. High Alt Med Biol 2024; 25:49-59. [PMID: 38011631 DOI: 10.1089/ham.2023.0084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023] Open
Abstract
Westwood, Jessica, India Mayhook-Walker, Ciaran Simpkins, Andrew Darby-Smith, Dan Morris, and Eduardo Normando. Retinal vascular changes in response to hypoxia: a high-altitude expedition study. High Alt Med Biol. 25:49-59, 2024. Background: Increased tortuosity and engorgement of retinal vasculature are recognized physiological responses to hypoxia. This can lead to high-altitude retinopathy (HAR), but incidence reports are highly variable, and our understanding of the etiological mechanisms remains incomplete. This study quantitatively evaluated retinal vascular changes during an expedition to 4,167 m. Methods: Ten healthy participants summited Mount Toubkal, Morocco. Fundus images were taken predeparture, daily throughout the expedition, and 1 month postreturn. Diameter and tortuosity of four vessels were assessed, in addition to vessel density and features of HAR. Results: Significant (p ≤ 0.05) increases in tortuosity and diameter were observed in several vessels on high-altitude exposure days. There was a strong correlation between altitude and supratemporal retinal artery diameter on days 2, 3, and 6 of the expedition (r = 0.7707, 0.7951, 0.7401, respectively; p < 0.05). There was a significant increase in median vessel density from 6.7% at baseline to 10.0% on summit day. Notably there were no incidences of HAR. Conclusion: Physiological but not pathological changes were seen in this cohort, which gives insight into the state of the cerebral vasculature throughout this expedition. These results are likely attributable to relatively low altitude exposure, a conservative ascent profile, and the cohort's demographic. Future study must include daily retinal images at higher altitudes and take steps to mitigate environmental confounders. This study is relevant to altitude tourists, patients with diabetic retinopathy or retinal vein occlusion, and critically ill patients.
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Affiliation(s)
- Jessica Westwood
- Imperial College London Ophthalmology Research Group, Western Eye Hospital, London, United Kingdom
| | - India Mayhook-Walker
- Imperial College London Ophthalmology Research Group, Western Eye Hospital, London, United Kingdom
| | - Ciaran Simpkins
- Imperial College London Ophthalmology Research Group, Western Eye Hospital, London, United Kingdom
| | - Andrew Darby-Smith
- Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom
| | - Dan Morris
- Cardiff Eye Unit, University Hospital of Wales, Cardiff, United Kingdom
| | - Eduardo Normando
- Imperial College London Ophthalmology Research Group, Western Eye Hospital, London, United Kingdom
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Retinal microvasculature is a potential biomarker for acute mountain sickness. SCIENCE CHINA. LIFE SCIENCES 2023:10.1007/s11427-022-2271-x. [PMID: 36811802 DOI: 10.1007/s11427-022-2271-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 12/21/2022] [Indexed: 02/24/2023]
Abstract
Increased cerebral blood flow resulting from altered capillary level autoregulation at high altitudes leads to capillary overperfusion and then vasogenic cerebral edema, which is the leading hypothesis of acute mountain sickness (AMS). However, studies on cerebral blood flow in AMS have been mostly restricted to gross cerebrovascular endpoints as opposed to the microvasculature. This study aimed to investigate ocular microcirculation alterations, the only visualized capillaries in the central neural system (CNS), during early-stage AMS using a hypobaric chamber. This study found that after high altitude simulation, the optic nerve showed retinal nerve fiber layer thickening (P=0.004-0.018) in some locations, and the area of the optic nerve subarachnoid space (P=0.004) enlarged. Optical coherence tomography angiography (OCTA) showed increased retinal radial peripapillary capillary (RPC) flow density (P=0.003-0.046), particularly on the nasal side of the nerve. The AMS-positive group had the largest increases in RPC flow density in the nasal sector (AMS-positive, Δ3.21±2.37; AMS-negative, Δ0.01±2.16, P=0.004). Among multiple ocular changes, OCTA increase in RPC flow density was associated with simulated early-stage AMS symptoms (beta=0.222, 95%CI, 0.009-0.435, P=0.042). The area under the receiver operating characteristics curve (AUC) for the changes in RPC flow density to predict early-stage AMS outcomes was 0.882 (95%CI, 0.746-0.998). The results further confirmed that overperfusion of microvascular beds is the key pathophysiologic change in early-stage AMS. RPC OCTA endpoints may serve as a rapid, noninvasive potential biomarker for CNS microvascular changes and AMS development during risk assessment of individuals at high altitudes.
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Hou J, Zheng D, Wen X, Xiao W, Han F, Lang H, Xiong S, Jiang W, Hu Y, He M, Long P. Proteomic and Morphological Profiling of Mice Ocular Tissue During High-altitude Acclimatization Process: An Animal Study at Lhasa. J Inflamm Res 2022; 15:2835-2853. [PMID: 35645575 PMCID: PMC9135145 DOI: 10.2147/jir.s361174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 04/27/2022] [Indexed: 12/31/2022] Open
Abstract
Purpose High-altitude environment mainly with hypobaric hypoxia could induce pathological alterations in ocular tissue. Previous studies have mostly focused on sporadic case reports and simulated high-altitude hypoxia experiments. This aim of this study was to explore the proteomic and morphological changes of ocular tissue in mice at real altitude environment. Methods In this study, mice were flown from Chengdu (elevation: 500 m) to Lhasa (elevation: 3600 m). After exposure for 1day, 3, 6, 10, 20, 30, and 40days, the mice were euthanatized to obtain blood and ocular tissue. Serological tests, ocular pathological examinations, integral ocular proteomics analysis, and Western blot were conducted. Results We focused on acute phase (1–3 days) and chronic phase (>30 days) during high-altitude acclimatization. Serum interleukin-1 was increased at 3 days, while superoxide dismutase, interleukin-6, and tumor necrosis factor-α showed no statistical changes. H&E staining demonstrated that the cornea was edematous at 3 days and exhibited slower proliferation at 30 days. The choroid showed a consistently significant thickening, while there existed no noticeable changes in retinal thickness. Overall, 4073 proteins were identified, among which 71 and 119 proteins were detected to have significant difference at 3 days and 40 days when compared with the control group. Functional enrichment analysis found the differentiated proteins at 3 days exposure functionally related with response to radiation, dephosphorylation, negative regulation of cell adhesion, and erythrocyte homeostasis. Moreover, the differential profiles of the proteins at 40 days exposure exhibited changes of regulation of complement activation, regulation of protein activation cascade, regulation of humoral immune response, second-messenger-mediated signaling, regulation of leukocyte activation, and cellular iron homeostasis. Interestingly, we found the ocular proteins with lactylation modification were increased along high-altitude adaptation. Conclusion This is the first work reporting the ocular proteomic and morphological changes at real high-altitude environment. We expect it would deep the understanding of ocular response during altitude acclimatization.
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Affiliation(s)
- Jun Hou
- Department of Cardiology, Chengdu Third People’s Hospital/Affiliated Hospital of Southwest Jiaotong University, Chengdu, People’s Republic of China
| | - Dezhi Zheng
- Department of Cardiovascular Surgery, the 960th Hospital of the PLA Joint Logistic Support Force, Jinan, People’s Republic of China
| | - Xudong Wen
- Department of Gastroenterology and Hepatology, Chengdu First People’s Hospital, Chengdu, People’s Republic of China
| | - Wenjing Xiao
- School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, People’s Republic of China
| | - Fei Han
- Department of Ophthalmology, the General Hospital of Western Theater Command, Chengdu, People’s Republic of China
| | - Hongmei Lang
- The Center of Obesity and Metabolic Diseases, Department of General Surgery, Chengdu Third People’s Hospital & the Affiliated Hospital of Southwest Jiaotong University, Chengdu, People’s Republic of China
| | - Shiqiang Xiong
- Department of Cardiology, Chengdu Third People’s Hospital/Affiliated Hospital of Southwest Jiaotong University, Chengdu, People’s Republic of China
| | - Wei Jiang
- Department of Ophthalmology, the General Hospital of Western Theater Command, Chengdu, People’s Republic of China
| | - Yonghe Hu
- School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, People’s Republic of China
- Yonghe Hu, School of Materials Science and Engineering, Southwest Jiaotong University, No. 111, North First Section of the Second Ring Road, Chengdu, People’s Republic of China, Tel +86-138-8059-6789, Email
| | - Mengshan He
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Pan Long
- School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, People’s Republic of China
- Department of Ophthalmology, the General Hospital of Western Theater Command, Chengdu, People’s Republic of China
- Correspondence: Pan Long, Department of Ophthalmology, the General Hospital of Western Theater Command, Rongdu Avenue #270, Chengdu, People’s Republic of China, Tel +86-181-9125-6132, Email
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Transcriptomic analysis of the mouse retina after acute and chronic normobaric and hypobaric hypoxia. Sci Rep 2021; 11:16666. [PMID: 34404875 PMCID: PMC8371159 DOI: 10.1038/s41598-021-96150-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 08/05/2021] [Indexed: 12/13/2022] Open
Abstract
Oxygen delivery to the retinal pigment epithelium and the outer retina is essential for metabolism, function, and survival of photoreceptors. Chronically reduced oxygen supply leads to retinal pathologies in patients and causes age-dependent retinal degeneration in mice. Hypoxia can result from decreased levels of inspired oxygen (normobaric hypoxia) or reduced barometric pressure (hypobaric hypoxia). Since the response of retinal cells to chronic normobaric or hypobaric hypoxia is mostly unknown, we examined the effect of six hypoxic conditions on the retinal transcriptome and photoreceptor morphology. Mice were exposed to short- and long-term normobaric hypoxia at 400 m or hypobaric hypoxia at 3450 m above sea level. Longitudinal studies over 11 weeks in normobaric hypoxia revealed four classes of genes that adapted differentially to the hypoxic condition. Seventeen genes were specifically regulated in hypobaric hypoxia and may affect the structural integrity of the retina, resulting in the shortening of photoreceptor segment length detected in various hypoxic groups. This study shows that retinal cells have the capacity to adapt to long-term hypoxia and that consequences of hypobaric hypoxia differ from those of normobaric hypoxia. Our datasets can be used as references to validate and compare retinal disease models associated with hypoxia.
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Auvazian SL, Cano J, Leahy S, Karamian P, Kashani A, Moshfeghi A, Ameri H, Blair NP, Shahidi M. Relating Retinal Vascular Oxygen Saturation and Microvasculature Morphology at Progressive Stages of Diabetic Retinopathy. Transl Vis Sci Technol 2021; 10:4. [PMID: 34111249 PMCID: PMC8107511 DOI: 10.1167/tvst.10.6.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Purpose Diabetic retinopathy (DR) is a common cause of vision loss in working age adults and presents changes in retinal vessel oxygenation and morphology. The purpose of this study was to test the hypothesis that there is an association of retinal vessel oxygen saturation with vessel density (VD) and tortuosity in DR. Methods Ninety-five subjects were classified in the following groups: nondiabetic control (N = 25), no DR (N = 28), mild nonproliferative DR (NPDR; N = 21), moderate to severe NPDR (N = 14), or treated proliferative DR (PDR; N = 7). Retinal oximetry was performed to measure arterial and venous oxygen saturation (SO2A and SO2V) and calculate oxygen extraction fraction (OEF). Optical coherence tomography angiography (OCTA) was performed for measurements of VD and vessel tortuosity index (VTI). Results There were statistically significant differences in SO2A and SO2V among groups (P< 0.004). SO2A and SO2V were higher in the PDR group compared to the control group and SO2V was also higher in the moderate to severe NPDR group. VD differed significantly among groups (P = 0.003), whereas VTI was not significantly different (P = 0.22). Compared to the control group, VD was lower in moderate to severe NPDR and PDR groups. VD was also lower in the PDR group than that in the no DR group (P = 0.03). There was a significant correlation of VTI with SO2V (r = 0.32, P = 0.002) and OEF (r = −0.35, P = 0.001). Conclusions Retinal vessel morphology, oxygenation, and tissue oxygen extraction were associated with each other in a cohort of subjects with and without DR. Translational Relevance The findings of this study have the potential to improve clinical management of DR by providing better understanding of human disease pathophysiology and propelling future studies to identify multiple image-based biomarkers for improved disease diagnosis and monitoring.
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Affiliation(s)
- Selin L Auvazian
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Jennifer Cano
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Preny Karamian
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Amir Kashani
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Andrew Moshfeghi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Hossein Ameri
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
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Vilela MA, Amaral CE, Ferreira MAT. Retinal vascular tortuosity: Mechanisms and measurements. Eur J Ophthalmol 2020; 31:1497-1506. [PMID: 33307777 DOI: 10.1177/1120672120979907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Retinal vessel tortuosity has been used in the diagnosis and management of different clinical situations. Notwithstanding, basic concepts, standards and tools of measurement, reliable normative data and clinical applications have many gaps or points of divergence. In this review we discuss triggering causes of retinal vessel tortuosity and resources used to assess and quantify it, as well as current limitations.
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Affiliation(s)
- Manuel Ap Vilela
- Federal University of Health Sciences of Porto Alegre, Porto Alegre, Brazil
| | - Carlos Ev Amaral
- Federal University of Health Sciences of Porto Alegre, Porto Alegre, Brazil
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McGrory S, Cameron JR, Pellegrini E, Warren C, Doubal FN, Deary IJ, Dhillon B, Wardlaw JM, Trucco E, MacGillivray TJ. The application of retinal fundus camera imaging in dementia: A systematic review. ALZHEIMER'S & DEMENTIA: DIAGNOSIS, ASSESSMENT & DISEASE MONITORING 2016; 6:91-107. [PMID: 28229127 PMCID: PMC5312461 DOI: 10.1016/j.dadm.2016.11.001] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Introduction The ease of imaging the retinal vasculature, and the evolving evidence suggesting this microvascular bed might reflect the cerebral microvasculature, presents an opportunity to investigate cerebrovascular disease and the contribution of microvascular disease to dementia with fundus camera imaging. Methods A systematic review and meta-analysis was carried out to assess the measurement of retinal properties in dementia using fundus imaging. Results Ten studies assessing retinal properties in dementia were included. Quantitative measurement revealed significant yet inconsistent pathologic changes in vessel caliber, tortuosity, and fractal dimension. Retinopathy was more prevalent in dementia. No association of age-related macular degeneration with dementia was reported. Discussion Inconsistent findings across studies provide tentative support for the application of fundus camera imaging as a means of identifying changes associated with dementia. The potential of fundus image analysis in differentiating between dementia subtypes should be investigated using larger well-characterized samples. Future work should focus on refining and standardizing methods and measurements.
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Affiliation(s)
- Sarah McGrory
- Centre for Clinical Brain Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
| | - James R Cameron
- Centre for Clinical Brain Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK; Anne Rowling Regenerative Neurology Clinic, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
| | - Enrico Pellegrini
- Centre for Clinical Brain Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
| | - Claire Warren
- College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
| | - Fergus N Doubal
- Centre for Clinical Brain Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
| | - Ian J Deary
- Department of Psychology, University of Edinburgh, Edinburgh, UK; Department of Psychology, Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK
| | - Baljean Dhillon
- Centre for Clinical Brain Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
| | - Joanna M Wardlaw
- Centre for Clinical Brain Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK; Department of Psychology, Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK; Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) Collaboration, Edinburgh, UK
| | - Emanuele Trucco
- VAMPIRE Project and Computer Vision and Image Processing Group School of Science and Engineering (Computing), University of Dundee, Dundee, UK
| | - Thomas J MacGillivray
- Centre for Clinical Brain Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK; VAMPIRE Project and Edinburgh Clinical Research Facility, University of Edinburgh, Edinburgh, UK
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Associations between Retinal Markers of Microvascular Disease and Cognitive Impairment in Newly Diagnosed Type 2 Diabetes Mellitus: A Case Control Study. PLoS One 2016; 11:e0147160. [PMID: 26771382 PMCID: PMC4714814 DOI: 10.1371/journal.pone.0147160] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 12/29/2015] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE To investigate associations between retinal microvascular changes and cognitive impairment in newly diagnosed type 2 diabetes mellitus. DESIGN Case control study. SETTING A primary care cohort with newly diagnosed type 2 diabetes mellitus. METHODS For this analysis, we compared 69 cases with lowest decile scores (for the cohort) on the Modified Telephone Interview for Cognitive Status and 68 controls randomly selected from the remainder of the cohort. Retinal images were rated and the following measures compared between cases and controls: retinal vessel calibre, arterio-venous ratio, retinal fractal dimension, and simple and curvature retinal vessel tortuosity. RESULTS Total and venular (but not arteriolar) simple retinal vessel tortuosity levels were significantly higher in cases than controls (t = 2.45, p = 0.015; t = 2.53, p = 0.013 respectively). The associations persisted after adjustment for demographic factors, retinopathy, neuropathy, obesity and blood pressure. There were no other significant differences between cases and controls in retinal measures. CONCLUSIONS A novel association was found between higher venular tortuosity and cognitive impairment in newly diagnosed type 2 diabetes mellitus. This might be accounted for by factors such as hypoxia, thrombus formation, increased vasoendothelial growth factor release and inflammation affecting both the visible retinal and the unobserved cerebral microvasculature.
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Gokce G, Metin S, Erdem U, Sobaci G, Durukan AH, Cagatay HH, Ekinci M. Late hyperbaric oxygen treatment of cilioretinal artery occlusion with nonischemic central retinal vein occlusion secondary to high altitude. High Alt Med Biol 2014; 15:84-8. [PMID: 24673536 DOI: 10.1089/ham.2013.1086] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIM To report a case of cilioretinal artery occlusion (CRAO) with central retinal vein occlusion (CRVO) after a journey to high altitude region and the use of late period hyperbaric oxygen (HBO) therapy successfully. CASE REPORT A previously healthy 48-year-old lowlander woman was admitted to our department for sudden blurred vision in her right eye started at 2 weeks prior to examination. The patient had a history of 1-month exposure to high altitude that finished a day before the onset of her complaints. The best corrected visual acuity (BCVA) was 10/20 in the right eye (RE) and 10/10 in the left eye. Fundus examination of the RE revealed whitening of the retina along the distribution of cilioretinal artery, sparing fovea, flame-shaped hemorrhages, and roth spots with minimally dilated and tortuous retinal veins. Visual field analysis revealed centrocecal scotoma. The patient was treated by a daily session of 2 h of HBO at 2.5 atmosphere absolute for 11 days. BCVA rised to a level of 20/20 for the RE and the scotomas were disappeared immediately after using of the HBO treatment. CONCLUSION CRVO related CRAO should be regarded as a rare complication of exposure to high altitude and HBO seems to be the treatment of choice of high altitude related co-occurence of CRVO and CRAO in the late period.
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Affiliation(s)
- Gokcen Gokce
- 1 Department of Ophthalmology, Sarikamis Military Hospital , Kars, Turkey
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Abstract
Altitude physiology began with Paul Bert in 1878. Chronic mountain sickness (CMS) was defined by Carlos Monge in the 1940s in the Peruvian Andes as consisting of excess polycythemia. Hurtado et al performed studies in the Peruvian Andes in the 1950s to 1960s which defined acclimatization in healthy altitude natives, including polycythemia, moderate pulmonary hypertension, and low systemic blood pressure (BP). Electrocardiographic changes of right ventricular hypertrophy (RVH) were noted. Acclimatization of newcomers to altitude involves hyperventilation stimulated by hypoxia and is usually benign. Acute mountain sickness (AMS) in travelers to altitude is characterized by hypoxia-induced anorexia, dyspnea, headache, insomnia, and nausea. The extremes of AMS are high-altitude cerebral edema and high-altitude pulmonary edema. The susceptible high-altitude resident can lose their tolerance to altitude and develop CMS, also referred to as Monge disease. The CMS includes extreme polycythemia, severe RVH, excess pulmonary hypertension, low systemic BP, arterial oxygen desaturation, and hypoventilation.
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Affiliation(s)
- Thomas F Whayne
- Division of Cardiovascular Medicine, Gill Heart Institute, University of Kentucky, Lexington, KY, USA
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Kadam RS, Ramamoorthy P, LaFlamme DJ, McKinsey TA, Kompella UB. Hypoxia alters ocular drug transporter expression and activity in rat and calf models: implications for drug delivery. Mol Pharm 2013; 10:2350-61. [PMID: 23607566 PMCID: PMC3973437 DOI: 10.1021/mp3007133] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Chronic hypoxia, a key stimulus for neovascularization, has been implicated in the pathology of proliferative diabetic retinopathy, retinopathy of prematurity, and wet age related macular degeneration. The aim of the present study was to determine the effect of chronic hypoxia on drug transporter mRNA expression and activity in ocular barriers. Sprague-Dawley rats were exposed to hypobaric hypoxia (PB = 380 mmHg) for 6 weeks, and neonatal calves were maintained under hypobaric hypoxia (PB = 445 mmHg) for 2 weeks. Age matched controls for rats, and calves were maintained at ambient altitude and normoxia. The effect of hypoxia on transporter expression was analyzed by qRT-PCR analysis of transporter mRNA expression in hypoxic and control rat choroid-retina. The effect of hypoxia on the activity of PEPT, OCT, ATB(0+), and MCT transporters was evaluated using in vitro transport studies of model transporter substrates across calf cornea and sclera-choroid-RPE (SCRPE). Quantitative gene expression analysis of 84 transporters in rat choroid-retina showed that 29 transporter genes were up regulated or down regulated by ≥1.5-fold in hypoxia. Nine ATP binding cassette (ABC) families of efflux transporters including MRP3, MRP4, MRP5, MRP6, MRP7, Abca17, Abc2, Abc3, and RGD1562128 were up-regulated. For solute carrier family transporters, 11 transporters including SLC10a1, SLC16a3, SLC22a7, SLC22a8, SLC29a1, SLC29a2, SLC2a1, SLC3a2, SLC5a4, SLC7a11, and SLC7a4 were up regulated, while 4 transporters including SLC22a2, SLC22a9, SLC28a1, and SLC7a9 were down-regulated in hypoxia. Of the three aquaporin (Aqp) water channels, Aqp-9 was down-regulated, and Aqp-1 was up-regulated during hypoxia. Gene expression analysis showed down regulation of OCT-1, OCT-2, and ATB(0+) and up regulation of MCT-3 in hypoxic rat choroid-retina, without any effect on the expression of PEPT-1 and PEPT-2. Functional activity assays of PEPT, OCT, ATB(0+), and MCT transporters in calf ocular tissues showed that PEPT, OCT, and ATB(0+) functional activity was down-regulated, whereas MCT functional activity was up-regulated in hypoxic cornea and SCRPE. Gene expression analysis of these transporters in rat tissues was consistent with the functional transport assays except for PEPT transporters. Chronic hypoxia results in significant alterations in the mRNA expression and functional activity of solute transporters in ocular tissues.
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Affiliation(s)
- Rajendra S. Kadam
- Pharmaceutical Sciences and Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO
| | | | | | - Timothy A. McKinsey
- Division of Cardiology and Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Uday B. Kompella
- Pharmaceutical Sciences and Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO
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