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Z. Pan, P. Gjorstrup, P. Reinach; Resolvins Inhibit Hypertonicity-Induced Proinflammatory Cytokine Release by Suppressing Mapk Pathway Activation in Human Corneal Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2008;49(13):125.
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Dry eye is commonly associated with tear film hypertonicity which may induce ocular surface inflammation and erosion. Accordingly, it is clinically relevant to identify novel approaches to suppress these stress responses. Resolvins, oxygenase products of omega-3 PUFAs, are highly potent and efficacious immune response regulators as shown in models of acute and chronic inflammation. We now investigated in human corneal epithelial cells (HCEC) if resolvin E1 (RvE1) and its analog RX-10008 could suppress a hypertonicity-induced increases in proinflammatory cytokine release.
SV-40 immortalized HCEC were maintained in DMEM/F12 medium supplemented with 10% FBS and 5 ng/ml epidermal growth factor (EGF). The extracellular medium tonicity was varied from 300 mOsm (isotonic control) to 600 mOsm by adding NaCl. Initial experiments indicated 450 mOsm was an optimal stress level with reproducible increases in cytokine levels and without causing cell detachment, and was the level selected for investigating effects of the resolvins. The HCEC were exposed to hypertonicity for 20 hours in the absence or presence of RvE1 and RX-10008 in concentrations between 10-11 - 10-7 M. The drugs were added 30 minutes prior to starting the hyperosmolar exposure. Q-Plux human inflammatory cytokine arrays were used to screen for select hypertonicity-induced cytokines, which were later quantitatively determined using ELISA.
Exposure to a hyperosmolar environment of 450 MOsm caused an increase in IL-6 levels from a basal level of approximately 2000 pg/mL to 4000 pg/mL, and for IL-8 the increase was from 3,700 pg/mL to 9000 pg/mL. Both RvE1 and RX-10008 in a concentration dependent manner prevented the release of both IL-6 and IL-8. At 10-7 M RvE1 reduced IL-6 release by 75% and IL-8 release by 70%, while the corresponding decreases seen with RX-10008 were 70% and 65%, respectively. There was no effect on IL-6 or IL-8 release by either compound at a concentration of 10-11 M.
Both RvE1 and its analogue RX-10008 in a concentration dependent manner suppress hypertonicity-induced release of IL-6 and IL-8 from HCEC. The results indicate that resolvins may have therapeutic value in the treatment of dry eye.
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