Abstract
Abstract: :
Purpose:We previously reported the use of an ex vivo model of bovine corneal organ culture for predicting acute ocular irritation and evaluating chemical toxicity. The present study sought to determine if corneal epithelial injury caused by surfactant exposure is reversible in ex vivo corneas and if recovery can be assessed quantitatively. Methods:Porcine corneas were cultured in an air lifting setting after center of the corneal epithelium exposed to a 7 mm diameter circular filter soaked in different concentrations of sodium dodecyl sulfate (SDS, 0.3, 1, 3, and 15%) or benzalkonium chloride (BAK, 0.1, 0.3, 1 and 3%) for 5 minutes. The corneas were cultured for 0, 1, 2, 3 or 4 days and then subject to surface biotinylation, fluorescein isothiocyanate-dextran retention and DNA-binding activities of AP-1 and NF-kB analyses. Results:Corneal epithelial injury can be recovered when exposed to surfactant with mild irritation (0.3, 1 and 3% SDS, Draize score <16.9), but no evidence of recovery was observed after exposed to surfactant with severe irritation (15% SDS, Draize score 59.2) as assessed by surface biotinylation. A correlation between Draize score and the recovery after BAK exposure can be observed although not as apparently as SDS treatment. The fluorescein retention was found increase in a concentration dependent manner in both SDS and BAK exposed corneas. Furthermore, AP-1 and NF-kB DNA-binding activities were altered. Two surfactants at concentrations to cause severe ocular irritation significantly and dramatically reduced AP-1 and NF-kB DNA-binding activities of corneal epithelial cells. Conclusion:Corneal epithelial barrier recovery after surfactant exposure was detectable in ex vivo corneal organ culture model. Prolonged corneal organ culture, in combination with the measurement of corneal epithelial permeability and DNA binding activity of stress-responsive transcription factors following chemical exposure, can be used as a mechanistically based alternative to in vivo animal testing.
Keywords: 494 ocular irritancy/toxicity testing • 372 cornea: epithelium • 605 transcription factors