title: Lacritin-induced secretion of tear proteins from cultured monkey lacrimal acinar cells.
abstract: OBJECTIVE
  During inflammation of the ocular surface, increased proinflammatory cytokines depress tear protein secretion, suggesting that a decline in lacrimal cell function contributes to dry eye. Lacritin, a glycoprotein secreted from lacrimal acinar cells, may function as an autocrine factor to stimulate tear protein secretion. The purpose of the present experiment was to investigate lacritin-induced protein secretion in normal and cytokine-pretreated (inflammation model) monkey acinar cells.
  
  
  METHODS
  Acinar cells from monkey lacrimal glands were cultured with or without tumor necrosis factor alpha (TNF-α) plus interferon gamma (IFN-γ). Protein secretion was induced by lacritin or carbachol (Cch, positive control). Proteins were detected and identified by immunoblotting and immunocytochemistry. Intracellular Ca(2+) was measured with the fluorophore Calcium-4, and cell damage was determined by LDH leakage into the culture medium.
  
  
  RESULTS
  In cultured monkey acinar cells, lacritin stimulated tear protein secretion in normal cells without elevating intracellular Ca(2+). In contrast, Cch elevated intracellular Ca(2+) and release of tear proteins. This contrast suggested an alternate, calcium-independent mechanism for lacritin-induced protein secretion. TNF-α plus IFN-γ caused LDH leakage from sensitive human corneal epithelial cells, but even higher doses of TNF-α plus IFN-γ did not cause LDH leakage from monkey acinar cells, suggesting a higher tolerance against these cytokines. In cytokine-treated acinar cells, lacritin stimulated protein secretion as much as that in normal cells. In contrast, Cch-induced elevation of Ca(2+) and release of proteins were depressed by cytokines.
  
  
  CONCLUSIONS
  Lacritin might be a useful biotechnology-based treatment agent against ocular surface diseases where endogenous lacritin is inadequate.
authors.affiliation: Senju Laboratory of Ocular Sciences, Senju Pharmaceutical Corporation Limited, Beaverton, Oregon 97006, USA.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Fujii
authors.forename: Ayumi
authors.initials: A
authors.lastname: Morimoto-Tochigi
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Walkup
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Shearer
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Azuma
mesh_terms: D061354:Acinar Cells / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000378:metabolism*; D006023:Glycoproteins / Q000302:isolation & purification / Q000494:pharmacology*; D015151:Immunoblotting; D007150:Immunohistochemistry; D007371:Interferon-gamma / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007765:Lacrimal Apparatus / Q000166:cytology*; D007781:Lactoferrin / Q000378:metabolism; D054834:Lipocalins / Q000378:metabolism; D008252:Macaca fascicularis; D008253:Macaca mulatta; D013666:Tears / Q000737:chemistry; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D005136:Eye Proteins; D006023:Glycoproteins; C431764:LACRT protein, human; D054834:Lipocalins; D014409:Tumor Necrosis Factor-alpha; C042434:tear proteins; D007371:Interferon-gamma; D002217:Carbachol; D007770:L-Lactate Dehydrogenase; D007781:Lactoferrin; D002118:Calcium