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Q. Liu, W. L. Miller, R. Redfern, A. M. McDermott; Effect of Nerve Growth Factor (NGF) and Hyperosmolar Stress on Corneal and Conjunctival Epithelial Cell Viability and Expression of Inflammation Related Molecules. Invest. Ophthalmol. Vis. Sci. 2008;49(13):432.
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© ARVO (1962-2015); The Authors (2016-present)
NGF modulates inflammation by altering production of cytokines such as TGF-β and may be beneficial in inflammatory conditions such as dry eye. A role for NGF in the relief of dry eye was sought by investigating its effects on expression of inflammation related molecules and cell viability in the presence and absence of hyperosmolar stress, a condition mimicking the dry eye environment.
SV40 transformed human corneal epithelial cells (SV40-HCEC) and human conjunctival epithelial cells (IOBA-NHC) were treated for 24 hrs with serum-free media of varying osmolality (300 - 500mOsm/kg) with or without NGF (10 or 100ng/ml). RT-PCR was performed to detect expression of TGF-β1 and 2, TLR4 and 9, HLA-DR, NGF and TrkA. TGF-β1 and 2 in culture supernatant and cell lysate were quantitated by ELISA. Cell viability was assessed by trypan blue exclusion test and MTT assay.
Hyperosmolar stress increased TGF-β1 (0.7-2 fold) and 2 (2-7 fold) mRNA expression in corneal and conjunctival epithelial cells (n=3). Parallel increases in TGF-β1 (0.3-1.5 fold) and 2 (2.5-8 fold) secretion were seen in SV40-HCEC (n=3). In NHC cells, TGF-β1 secretion was increased 2.5-8 fold (n=3). TGF-β2 was not detected in culture supernatant, but increased 0.9-3 fold in NHC cell lysate (n=3). TLR4 mRNA increased (0.7-4 fold, n=4) with hyperosmolar stress whereas TLR9 and HLA-DR mRNA were slightly decreased (n=3). Compared to hyperosmolar media alone NGF: 1).increased TGF-β1 and 2 mRNA up to 30% in both cell types (n=3); 2).increased TGF-β1 (up to 80%) and 2 (up to 200%) secretion in SV40-HCEC (n=3); 3).did not affect TGF-β2 protein levels in NHC cell lysate (n=3) and 4).slightly decreased TLR4, 9, and HLA-DR mRNA expression. NGF mRNA expression was not modulated by NGF treatment whilst, TrkA mRNA was up-regulated 3-8 fold (n=3). 500mOsm/kg induced approximately 35% death in both cell types and 72% of this was prevented by NGF.
The results suggest that NGF, acting via TrkA, may have beneficial effects in dry eye by modulating ocular surface epithelial cell expression of inflammation related molecules and by reducing epithelial cell death.
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