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Ningning Wang, Keith Zimmerman, Jae K. Lee, Robert L. McKown, Gordon W. Laurie; Lacritin Suppression of Inflammatory Stress Involves Rapid Changes in the Human Corneal Epithelial Cell Metabolome. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4230.
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The human prosecretory tear protein lacritin is protective against INFG and TNF in human corneal epithelial cell culture via AKT/FOXO3 survival signaling. Both INFG and TNF are elevated in dry eye tears. Since FOXO3 is an important regulator of cellular metabolism, we asked here whether signature metabolic changes underlie lacritin survival signaling.
Human corneal epithelial (HCE; Riken) cells were sensitized with INFG, and then treated with TNF in the (i) absence or presence of (ii)10 nM lacritin or (iii) inactive C-25 lacritin for 10 min and flash frozen Experiments were performed in replicates of six with at least one million cells per replicate. Flash frozen cells were subjected to unbiased metabolomic analysis by LC/MS and GC/MS (Metabolon), and metabolite values were assessed by two sample t- and non-parametric Wilcoxen tests of the log transformed normalized data comparing (ii) lacritin or (iii) C-25 cells to (i) TNF alone treated cells. Data significant by both tests (p<0.05) were then analyzed by hierarchical clustering.
Of 138 metabolites examined, lacritin decreased 22 and increased 7 metabolites. The implication is that protein anabolism and acetylation are increased. Anabolism may feed off of autophagic catabolites. Also elevated are glycerolphosphoinositols and glycerolphosphoethanolamines. Interestingly, the tryptophan metabolite kynurenine is suppressed. Kynurenine is elevated in Sjögren’s syndrome, rheumatoid arthritis and other autoimmune disease sera.
Lacritin promotes rapid metabolic changes in stressed human corneal epithelial cells, suggesting that survival signaling is a complex mixture of kinase activation and metabolic realignment.
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