Comparison of antioxidant enzymes genes expression changes in conjunctival epithelium induced by non ionic hydrogel contact lenses with different oxigen permeability.

Abstract

Abstract: : Purpose: To investigate whether oxigen permeability in non ionic hydrogel contact lenses (HCL) may have influence in the alteration of the expression of 6 of the most relevant antioxidant enzymes genes in the human conjunctival epithelium after one year of wear. Methods: Sixteen healthy subjects with no history of contact lens wear were selected. Patients were randomized into two groups. Group 1: 8 patients (16 eyes) fitted with low permeability (dK 9) non ionic HCL; group 2: 8 patients (16 eyes) fitted with high permeability (dK 32) non ionic HCL. Conjunctival impression cytology was performed by applying two polyethersulfone filters to the superior bulbar conjunctiva of both eyes before HCL fitting, and at 6 months, 1 year and 15 days after discontinuation of wear. Real time polymerase chain reaction was performed using isolated and retrotranscribed total RNA to quantify the expression of 6 antioxidant enzymes genes: cytosolic Cu and Zn containing superoxide dismutase (CuZn–SOD), mitochondrial Mn superoxide dismutase (Mn–SOD), extracellular superoxide dismutase (ec–SOD), glutathione synthetase (GSS), glutathione reductase (GSR) and catalase. 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: No differences were found between both groups. Mn SOD expression showed no changes in both groups. Catalase, CuZn–SOD, GSS and GSR expression diminished in both groups (p<0.05) after 6 or 12 months of HCL wear. Transcripts of ec–SOD increased in group 1 (p<0.01) but remained stable in group 2 after 6 or 12 months of HCL wear. Fifteen days after discontinuing HCL wear, all transcripts did not change compared with the previous visit. However, CuZn–SOD, GSS and GSR expression remained reduced compared with the initial transcripts (p<0.01). Conclusions: Oxigen permeability did not influence in the changes induced by non ionic HCL wear in the 6 antioxidant enzymes genes tested. However, non ionic HCL wear might decrease the resistence of the conjunctival epithelium to oxidative stress.

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