{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:16:47Z","timestamp":1760235407527,"version":"build-2065373602"},"reference-count":36,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,8,19]],"date-time":"2021-08-19T00:00:00Z","timestamp":1629331200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["80NSSC18K0310","80NSSC18K0785","NNX15AB41G"],"award-info":[{"award-number":["80NSSC18K0310","80NSSC18K0785","NNX15AB41G"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Life"],"abstract":"<jats:p>There are serious concerns about possible late radiation damage to ocular tissue from prolonged space radiation exposure, and occupational and medical procedures. This study aimed to investigate the effects of whole-body high-energy proton exposure at a single dose on apoptosis, oxidative stress, and blood-retina barrier (BRB) integrity in the retina and optic nerve head (ONH) region and to compare these radiation-induced effects with those produced by fractionated dose. Six-month-old C57BL\/6 male mice were either sham irradiated or received whole-body high energy proton irradiation at an acute single dose of 0.5 Gy or 12 equal dose fractions for a total dose of 0.5 Gy over twenty-five days. At four months following irradiation, mice were euthanized and ocular tissues were collected for histochemical analysis. Significant increases in the number of apoptotic cells were documented in the mouse retinas and ONHs that received proton radiation with a single or fractionated dose (p &lt; 0.05). Immunochemical analysis revealed enhanced immunoreactivity for oxidative biomarker, 4-hydroxynonenal (4-HNE) in the retina and ONH following single or fractionated protons with more pronounced changes observed with a single dose of 0.5 Gy. BRB integrity was also evaluated with biomarkers of aquaporin-4 (AQP-4), a water channel protein, a tight junction (TJ) protein, Zonula occludens-1 (ZO-1), and an adhesion molecule, the platelet endothelial cell adhesion molecule-1 (PECAM-1). A significantly increased expression of AQP-4 was observed in the retina following a single dose exposure compared to controls. There was also a significant increase in the expression of PECAM-1 and a decrease in the expression of ZO-1 in the retina. These changes give a strong indication of disturbance to BRB integrity in the retina. Interestingly, there was very limited immunoreactivity of AQP-4 and ZO-1 seen in the ONH region, pointing to possible lack of BRB properties as previously reported. Our data demonstrated that exposure to proton radiation of 0.5 Gy induced oxidative stress-associated apoptosis in the retina and ONH, and changes in BRB integrity in the retina. Our study also revealed the differences in BRB biomarker distribution between these two regions. In response to radiation insults, the cellular response in the retina and ONH may be differentially regulated in acute or hyperfractionated dose schedules.<\/jats:p>","DOI":"10.3390\/life11080849","type":"journal-article","created":{"date-parts":[[2021,8,19]],"date-time":"2021-08-19T09:58:06Z","timestamp":1629367086000},"page":"849","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Evaluating Ocular Response in the Retina and Optic Nerve Head after Single and Fractionated High-Energy Protons"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4508-8689","authenticated-orcid":false,"given":"Xiao-Wen","family":"Mao","sequence":"first","affiliation":[{"name":"Department of Basic Sciences, Division of Biomedical Engineering Sciences (BMES), Loma Linda University School of Medicine and Medical Center, Loma Linda, CA 92350, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Seta","family":"Stanbouly","sequence":"additional","affiliation":[{"name":"Department of Basic Sciences, Division of Biomedical Engineering Sciences (BMES), Loma Linda University School of Medicine and Medical Center, Loma Linda, CA 92350, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tamako","family":"Jones","sequence":"additional","affiliation":[{"name":"Department of Basic Sciences, Division of Biomedical Engineering Sciences (BMES), Loma Linda University School of Medicine and Medical Center, Loma Linda, CA 92350, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gregory","family":"Nelson","sequence":"additional","affiliation":[{"name":"Department of Basic Sciences, Division of Biomedical Engineering Sciences (BMES), Loma Linda University School of Medicine and Medical Center, Loma Linda, CA 92350, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,19]]},"reference":[{"key":"ref_1","unstructured":"National Research Council (2008). Managing Space Radiation Risk in the New Era of Space Exploration, National Academies Press."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"241","DOI":"10.1667\/RR15219.1","article-title":"Combined Effects of Low-Dose Proton Radiation and Simulated Microgravity on the Mouse Retina and the Hematopoietic System","volume":"192","author":"Mao","year":"2018","journal-title":"Radiat. Res."},{"key":"ref_3","first-page":"425","article-title":"Gene expression analysis of oxidative stress and apoptosis in proton-irradiated rat retina","volume":"24","author":"Mao","year":"2010","journal-title":"In Vivo"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1667\/RR14977.1","article-title":"Acute Effect of Low-Dose Space Radiation on Mouse Retina and Retinal Endothelial Cells","volume":"190","author":"Mao","year":"2018","journal-title":"Radiat. Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"353","DOI":"10.1667\/RR1398.1","article-title":"Dietary Supplements Reduce the Cataractogenic Potential of Proton and HZE-Particle Radiation in Mice","volume":"173","author":"Davis","year":"2010","journal-title":"Radiat. Res."},{"key":"ref_6","first-page":"1","article-title":"Spaceflight associated neuro-ocular syndrome (SANS) and the neuro-ophthalmologic effects of microgravity: A review and an update","volume":"6","author":"Lee","year":"2020","journal-title":"NPJ Microgravity"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1604","DOI":"10.1016\/j.ophtha.2019.09.009","article-title":"Focus on the Optic Nerve Head in Spaceflight-Associated Neuro-ocular Syndrome","volume":"126","author":"Stenger","year":"2019","journal-title":"Ophthalmology"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Simonsen, L.C., Slaba, T.C., Guida, P., and Rusek, A. (2020). NASA\u2019s first ground-based Galactic Cosmic Ray Simulator: Enabling a new era in space radiobiology research. PLoS Biol., 18.","DOI":"10.1371\/journal.pbio.3000669"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1177\/15330346070060S411","article-title":"Development and operation of the Loma Linda University Medical Center proton facility","volume":"6","author":"Slater","year":"2007","journal-title":"Technol. Cancer Res. Treat."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"463","DOI":"10.1016\/j.scitotenv.2016.01.027","article-title":"Ionizing radiation, antioxidant response and oxidative damage: A meta-analysis","volume":"548","author":"Einor","year":"2016","journal-title":"Sci. Total Environ."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"C537","DOI":"10.1152\/ajpcell.00101.2016","article-title":"4-Hydroxy-2-nonenal: A critical target in oxidative stress?","volume":"311","author":"Breitzig","year":"2016","journal-title":"Am. J. Physiol. Cell Physiol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"319","DOI":"10.18388\/abp.2003_3689","article-title":"Lipid peroxidation and cell cycle signaling: 4-hydroxynonenal, a key molecule in stress mediated signaling","volume":"50","author":"Yang","year":"2003","journal-title":"Acta Biochim. Pol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1016\/j.freeradbiomed.2016.11.033","article-title":"Antioxidants and HNE in redox homeostasis","volume":"111","author":"Skrzydlewska","year":"2017","journal-title":"Free Radic. Biol. Med."},{"key":"ref_14","unstructured":"National Cancer Institute (2021, May 12). Hyperfractionated radiation therapy, NCI Dictionary of Cancer Terms, Available online: https:\/\/www.cancer.gov\/publications\/dictionaries\/cancer-terms\/def\/hyperfractionated-radiation-therapy."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1155","DOI":"10.1016\/S0360-3016(00)00754-9","article-title":"Dose response of rat retinal microvessels to proton dose schedules used clinically: A pilot study","volume":"48","author":"Archambeau","year":"2000","journal-title":"Int. J. Radiat. Oncol."},{"key":"ref_16","unstructured":"Horneck, G., and Stassinopoulos, E.G. (1993). Effects of Linear Energy Transfer on the Formation and Fate of Radiation Damage to the Photoreceptor Cell Complement of the Rabbit Retina: Implications for the Projected Manned Mission to Mars. Biological Effects and Physics of Solar and Galactic Cosmic Radiation, Springer."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1080\/09553008314550281","article-title":"Effects of Heavy Ions on Rabbit Tissues: Analysis of Low Levels of DNA Damage in Retinal Photoreceptor Cells","volume":"43","author":"Keng","year":"1983","journal-title":"Int. J. Radiat. Biol. Relat. Stud. Phys. Chem. Med."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/j.exer.2012.05.012","article-title":"Characterization of retinal expression of vascular cell adhesion molecule (VCAM-1) during experimental autoimmune uveitis","volume":"101","author":"Makhoul","year":"2012","journal-title":"Exp. Eye Res."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"484","DOI":"10.1016\/j.yjmcc.2006.01.022","article-title":"Triglyceride-rich lipoproteins from hypertriglyceridemic subjects induce a pro-inflammatory response in the endothelium: Molecular mechanisms and gene expression studies","volume":"40","author":"Norata","year":"2006","journal-title":"J. Mol. Cell. Cardiol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1172","DOI":"10.1182\/blood-2009-12-256388","article-title":"CD99 and CD99L2 act at the same site as, but independently of, PECAM-1 during leukocyte diapedesis","volume":"116","author":"Bixel","year":"2010","journal-title":"Blood"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1097\/MOH.0000000000000239","article-title":"Endothelial functions of platelet\/endothelial cell adhesion molecule-1 (CD31)","volume":"23","author":"Lertkiatmongkol","year":"2016","journal-title":"Curr. Opin. Hematol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2416","DOI":"10.7150\/ijms.48635","article-title":"Metformin reverses the drug resistance of cisplatin in irradiated CNE-1 human nasopharyngeal carcinoma cells through PECAM-1 mediated MRPs down-regulation","volume":"17","author":"Sun","year":"2020","journal-title":"Int. J. Med. Sci."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1089\/jop.2012.0179","article-title":"Baicalein Protects against Retinal Ischemia by Antioxidation, Antiapoptosis, Downregulation of HIF-1\u03b1, VEGF, and MMP-9 and Upregulation of HO-1","volume":"29","author":"Chao","year":"2013","journal-title":"J. Ocul. Pharmacol. Ther."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"326","DOI":"10.1016\/S1471-4906(03)00117-0","article-title":"Leukocyte\u2013endothelial-cell interactions in leukocyte transmigration and the inflammatory response","volume":"24","author":"Muller","year":"2003","journal-title":"Trends Immunol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"52","DOI":"10.4103\/0974-9233.92116","article-title":"Diabetic retinopathy and inflammation: Novel therapeutic targets","volume":"19","author":"Das","year":"2012","journal-title":"Middle East Afr. J. Ophthalmol."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Naylor, A., Hopkins, A., Hudson, N., and Campbell, M. (2019). Tight Junctions of the Outer Blood Retina Barrier. Int. J. Mol. Sci., 21.","DOI":"10.3390\/ijms21010211"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1146\/annurev.cellbio.22.010305.104219","article-title":"Tight Junctions and Cell Polarity","volume":"22","author":"Shin","year":"2006","journal-title":"Annu. Rev. Cell Dev. Biol."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Tong, N., Zhang, Z., Zhang, W., Qiu, Y., Gong, Y., Yin, L., Qiu, Q., and Wu, X. (2013). Diosmin Alleviates Retinal Edema by Protecting the Blood-Retinal Barrier and Reducing Retinal Vascular Permeability during Ischemia\/Reperfusion Injury. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0061794"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"8215","DOI":"10.1038\/s41598-019-44696-0","article-title":"Characterization of mouse ocular response to a 35-day spaceflight mission: Evidence of blood-retinal barrier disruption and ocular adaptations","volume":"9","author":"Mao","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"573","DOI":"10.1073\/pnas.1912546116","article-title":"Ultraviolet A light induces DNA damage and estrogen-DNA adducts in Fuchs endothelial corneal dystrophy causing females to be more affected","volume":"117","author":"Liu","year":"2019","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"756","DOI":"10.1097\/IJG.0000000000001293","article-title":"Gravitational Influence on Intraocular Pressure: Implications for Spaceflight and Disease","volume":"28","author":"Huang","year":"2019","journal-title":"J. Glaucoma"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"663","DOI":"10.1001\/jamaophthalmol.2021.0931","article-title":"Changes in the Optic Nerve Head and Choroid Over 1 Year of Spaceflight","volume":"139","author":"Macias","year":"2021","journal-title":"JAMA Ophthalmol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"781","DOI":"10.1001\/jamaophthalmol.2021.1400","article-title":"Association of Structural Changes in the Brain and Retina after Long-Duration Spaceflight","volume":"139","author":"Macias","year":"2021","journal-title":"JAMA Ophthalmol."},{"key":"ref_34","first-page":"895","article-title":"Lack of blood-brain barrier properties in microvessels of the prelaminar optic nerve head","volume":"42","author":"Hofman","year":"2001","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1016\/j.bbi.2020.12.026","article-title":"Platelet endothelial cell adhesion molecule-1 is a gatekeeper of neutrophil transendothelial migration in ischemic stroke","volume":"93","author":"Winneberger","year":"2020","journal-title":"Brain Behav. Immun."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1089","DOI":"10.3357\/AMHP.5095.2018","article-title":"Dilated Prelaminar Paravascular Spaces as a Possible Mechanism for Optic Disc Edema in Astronauts","volume":"89","author":"Wostyn","year":"2018","journal-title":"Aerosp. Med. Hum. Perform."}],"container-title":["Life"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-1729\/11\/8\/849\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:47:15Z","timestamp":1760165235000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-1729\/11\/8\/849"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,19]]},"references-count":36,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["life11080849"],"URL":"https:\/\/doi.org\/10.3390\/life11080849","relation":{},"ISSN":["2075-1729"],"issn-type":[{"type":"electronic","value":"2075-1729"}],"subject":[],"published":{"date-parts":[[2021,8,19]]}}}