PURPOSE. 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-a) plus interferon gamma (IFN-c). Protein secretion was induced by lacritin or carbachol (Cch, positive control). Proteins were detected and identified by immunoblotting and immunocytochemistry. Intracellular Ca 2þ 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 2þ. In contrast, Cch elevated intracellular Ca 2þ and release of tear proteins. This contrast suggested an alternate, calcium-independent mechanism for lacritin-induced protein secretion. TNF-a plus IFN-c caused LDH leakage from sensitive human corneal epithelial cells, but even higher doses of TNF-a plus IFN-c 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 2þ 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.

Successful culture of monkey lacrimal acinar cells showed that, among the prevalent tear proteins, the secretion of lacritin involved the PKC/Ca2+ pathway, not the p42/p44 MAPK pathway. Induction of transcription by Cch involved the independent p42/p44 MAPK and PKC pathways.