Levels of Antioxidant Enzyme Genes in Conjunctival Impression Cytology Specimens from Hydrogel Contact Lenses Wearers

Abstract

Abstract: : Purpose:To investigate whether hydrogel contact lens (HCL) wearing induces alterations in the expression of 5 of the most relevant antioxidant enzyme genes in the human conjunctival epithelium. Methods:Conjunctival impression cytology was performed by applying two polyethersulfone filters to the superior bulbar conjunctiva of both eyes of 8 healthy donors who never had worn contact lenses before, 6 months, and 1 year after HCL fitting, and 15 days after discontinuation. Real time PCR was performed using isolated and retrotranscribed total RNA to quantify the expression of 5 antioxidant enzyme genes: mitochondrial Mn superoxide dismutase (MnSOD), cytosolic Cu- and Zn-containing superoxide dismutase (CuZn-SOD), extracellular superoxide dismutase (ecSOD), glutathione synthetase (GSS), and glutathione reductase (GSR). The relative quantity of these mRNAs was determined by SYBR ® Green I dye detection. The housekeeping gene GAPDH was used to normalize the amount of expression levels. Chronologic variations were analyzed using Student's test and lineal regression. Results:Expression of all genes showed a tendency to diminish after 6 and 12 months of HCL wearing, although only significant for CuZn-SOD (p<0.05), and for GSS and GSR (p<0.0001). Fifteen days after discontinuing HCL wearing, ecSOD gene levels remained unaltered, whereas the other genes had a tendency to increase, being significant (p<0.05) for GSS and GSR transcripts. Conclusions: HCL wearing for 12 months decreased the expression of 3 out of the 5 antioxidant enzyme genes studied. These findings suggest that HCL wearing might decrease the defensive capacity of the normal conjunctiva against oxidative stress.

Keywords: oxidation/oxidative or free radical damage • contact lens • conjunctiva