Osmoprotective activity of alpha-lipoic acid and taurine on hyperosmolar stress in cultured human corneal and conjunctival epithelial cells

PurposeTo characterize the osmoprotective properties of α-lipoic acid (ALA) alone and in combination with taurine on both human corneal and conjunctival epithelial cells for cell viability and inflammatory biomarkers regulation after hyperosmotic stress.MethodsHuman corneal epithelial (HCE) cells and conjunctival epithelial (WKD) cells were incubated in isotonic media and hyperosmolar media (by addition of 100 mM NaCl), in the presence and absence of ALA, Taurine and ALA + Taurine. The osmoprotective activity on cell viability after 4, 8 and 24 h of hyperosmolar stress was evaluated by XTT assay. The expression of inflammatory biomarkers in cell-free supernatants was measured using a Human Cytokine 15-plex ELISA Kit after 4 and 8 h of stress.ResultsThe hyperosmolar conditions significantly reduced the cell viability in a time-dependent manner and induced an overexpression of a panel of cytokines in corneal and conjunctival cells. Preincubation of cells with ALA alone or in combination with taurine significantly lowered the cell toxicity induced by the stress. The highest cell viability protection was observed within the range of ALA/Taurine ratios from 0.005 to 0.05 in conjunctival cells. In corneal cells the combination of ALA + Taurine, exhibited a higher osmoprotective effect than ALA or Taurine alone. The expression of cytokines was significantly but differentially reduced by ALA, and ALA + Taurine in corneal and conjunctival cells. The combination of ALA + Taurine exhibited a higher anti-inflammatory effect than ALA or Taurine alone in corneal cells exposed to stress.ConclusionsALA alone or in combination with taurine, was found to protect against cytotoxicity and inflammation of corneal and conjunctival epithelial cells cultured in hyperosmolar media. ALA may have potential effects in protecting ocular surface epithelia from hyperosmotic stress.