{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T20:15:34Z","timestamp":1790194534330,"version":"4.1.0"},"reference-count":20,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T00:00:00Z","timestamp":1773360000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>Feline conjunctivitis is a common ocular disorder; however, the molecular composition of feline tear fluid and its alterations during ocular surface inflammation remain poorly characterized. This pilot study aimed to explore the tear proteome of cats with conjunctivitis using matrix-assisted laser desorption\/ionization time-of-flight tandem mass spectrometry (MALDI\u2013TOF\/TOF MS) and to compare findings with those from clinically healthy cats. Tear samples were collected using Schirmer tear test strips from healthy cats and cats diagnosed with conjunctivitis. Total protein concentration was measured by ultraviolet absorbance spectrophotometry, and tear proteins were separated by SDS\u2013polyacrylamide gel electrophoresis, followed by in-gel trypsin digestion and MALDI\u2013TOF\/TOF MS analysis. Nine distinct tear proteins were identified, including antimicrobial and immune-related components such as lactoperoxidase, lactotransferrin, albumin, and immunoglobulin A constant region. Lactoperoxidase and SBP1 were identified in feline tear fluid for the first time. No proteins uniquely associated with conjunctivitis were detected. The mean total tear protein concentration was numerically higher in cats with conjunctivitis (13.06 \u00b1 0.75 mg\/mL) than in healthy cats (9.69 \u00b1 0.67 mg\/mL); however, this difference did not reach statistical significance (p = 0.095) and should be interpreted cautiously given the limited sample size. This pilot study provides preliminary insights into tear protein profiles in cats with conjunctivitis and highlights the need for larger quantitative investigations. These findings provide a preliminary framework for future studies aimed at further characterizing molecular alterations associated with feline ocular surface disorders.<\/jats:p>","DOI":"10.3390\/ani16060912","type":"journal-article","created":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T15:06:22Z","timestamp":1773414382000},"page":"912","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A Pilot Proteomic Analysis of Tear Fluid in Domestic Cats with and Without Conjunctivitis Using MALDI\u2013TOF\/TOF Mass Spectrometry"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-5212-3221","authenticated-orcid":false,"given":"Takuya","family":"Yogo","sequence":"first","affiliation":[{"name":"Laboratory of Veterinary Surgery, Nippon Veterinary and Life Science University, Musashino 180-8602, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shotaro","family":"Iino","sequence":"additional","affiliation":[{"name":"Laboratory of Veterinary Surgery, Nippon Veterinary and Life Science University, Musashino 180-8602, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0667-6736","authenticated-orcid":false,"given":"Kinya","family":"Katayama","sequence":"additional","affiliation":[{"name":"Laboratory of Biomolecular Chemistry, Nippon Veterinary and Life Science University, Musashino 180-8602, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Sebbag, L., Allbaugh, R.A., Weaver, A., Seo, Y.J., and Mochel, J.P. (2019). Histamine-induced conjunctivitis and breakdown of blood\u2013tear barrier in dogs: A model for ocular pharmacology and therapeutics. Front. Pharmacol., 10.","DOI":"10.3389\/fphar.2019.00752"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"683","DOI":"10.1111\/vop.13261","article-title":"Tear cytokines as potential markers of inflammation in feline conjunctivitis","volume":"28","author":"Davari","year":"2025","journal-title":"Vet. Ophthalmol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"9982","DOI":"10.1002\/jcp.27895","article-title":"Tears and ocular surface disorders: Usefulness of biomarkers","volume":"234","author":"Micera","year":"2019","journal-title":"J. Cell. Physiol."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Winiarczyk, M., Winiarczyk, D., Banach, T., Adaszek, L., Madany, J., Mackiewicz, J., Pietras-Ozga, D., and Winiarczyk, S. (2015). Dog tear film proteome in-depth analysis. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0144242"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"333","DOI":"10.1016\/j.jfms.2011.03.010","article-title":"Feline herpesvirus-1: Ocular manifestations, diagnosis and treatment options","volume":"13","author":"Gould","year":"2011","journal-title":"J. Feline Med. Surg."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Gelatt, K.N. (2021). Feline ophthalmology. Veterinary Ophthalmology, John Wiley & Sons. [6th ed.].","DOI":"10.1002\/9781119801368"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"842","DOI":"10.1002\/mas.21691","article-title":"Mass spectrometry-based tear proteomics for noninvasive biomarker discovery","volume":"41","author":"Ponzini","year":"2022","journal-title":"Mass Spectrom. Rev."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Nattinen, J., Aapola, U., Nukareddy, P., and Uusitalo, H. (2022). Clinical tear fluid proteomics-A novel tool in glaucoma research. Int. J. Mol. Sci., 23.","DOI":"10.3390\/ijms23158136"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Ritchoo, S., Havanapan, P.O., Phungthanom, N., Rucksaken, R., Muikaew, R., and Sussadee, M. (2022). Analysis and comparison of tear protein profiles in dogs using different tear collection methods. BMC Vet. Res., 18.","DOI":"10.1186\/s12917-022-03543-7"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"384","DOI":"10.1002\/pro.4230","article-title":"Structural evidence of the oxidation of iodide ion into hyper-reactive hypoiodite ion by mammalian heme lactoperoxidase","volume":"31","author":"Singh","year":"2022","journal-title":"Protein Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"447","DOI":"10.1517\/14728222.2016.1112378","article-title":"Lactoperoxidase as a potential drug target","volume":"20","author":"Flemmig","year":"2016","journal-title":"Expert Opin. Ther. Targets"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Elhodaky, M., and Diamond, A.M. (2018). Selenium-binding protein 1 in human health and disease. Int. J. Mol. Sci., 19.","DOI":"10.3390\/ijms19113437"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"8708023","DOI":"10.1155\/2021\/8708023","article-title":"Tear film proteome of healthy domestic cats","volume":"2021","author":"Veloso","year":"2021","journal-title":"Vet. Med. Int."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1490","DOI":"10.1111\/all.12955","article-title":"The cat lipocalin Fel d 7 and its cross-reactivity with the dog lipocalin Can f 1","volume":"71","author":"Apostolovic","year":"2016","journal-title":"Allergy"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"967","DOI":"10.1124\/pr.111.004523","article-title":"The conserved scavenger receptor cysteine-rich superfamily in therapy and diagnosis","volume":"63","author":"Martinez","year":"2011","journal-title":"Pharmacol. Rev."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"38","DOI":"10.1615\/CritRevImmunol.v24.i1.10","article-title":"The Scavenger Receptor Cysteine-Rich (SRCR) domain: An ancient and highly conserved protein module of the innate immune system","volume":"24","author":"Sarrias","year":"2004","journal-title":"Crit. Rev. Immunol."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Comito, R., Ciavarella, C., Astolfi, G., Conti, M., Porru, E., Violante, F.S., and Versura, P. (2025). Tear Sampling and Biomarker Discovery: A Robust Workflow for Routine Clinical Applications Using UHPLC-MS\/MS and Schirmer Strips. Int. J. Mol. Sci., 26.","DOI":"10.3390\/ijms26052041"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"31181","DOI":"10.1038\/s41598-025-17105-y","article-title":"High throughput tear proteomics with data independent acquisition enables biomarker discovery in allergic conditions","volume":"15","author":"Pardo","year":"2025","journal-title":"Sci. Rep."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"406","DOI":"10.1002\/prca.201400130","article-title":"ELISA in the multiplex era: Potentials and pitfalls","volume":"9","author":"Tighe","year":"2015","journal-title":"Proteom. Clin. Appl."},{"key":"ref_20","unstructured":"Wild, D. (2013). Immunoassay Performance Measures. The Immunoassay Handbook: Theory and Applications of Ligand Binding, ELISA and Related Techniques, Elsevier. [4th ed.]. Chapter 1.3."}],"container-title":["Animals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/6\/912\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T15:16:20Z","timestamp":1773414980000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/6\/912"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,13]]},"references-count":20,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2026,3]]}},"alternative-id":["ani16060912"],"URL":"https:\/\/doi.org\/10.3390\/ani16060912","relation":{},"ISSN":["2076-2615"],"issn-type":[{"value":"2076-2615","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,13]]}}}