Antioxidant enzyme mRNA expression in conjunctival epithelium of healthy human subjects

To determine the profile, relative quantitation, and correlation of gene expression of the antioxidant enzymes copper-zinc superoxide dismutase (CuZn-SOD), Mn-superoxide dismutase (Mn-SOD), extracellular superoxide dismutase (EC-SOD), catalase (CAT), glutathione synthetase (GSS), and glutathione reductase (GSR) in conjunctival samples from healthy subjects.

Descriptive study.

Sixteen healthy donors (32 eyes) were included in this study.

Conventional and real-time polymerase chain reactions (PCR) were performed using total RNA isolated from conjunctival impression cytology taken from bulbar superior conjunctiva from both eyes.

Products amplified by conventional PCR had only 1 band with the expected size for each target gene. Melt-curve analysis of real-time PCR products also identified a single amplified product for each gene. Log-transformed antioxidant enzyme mRNA expression levels, relative to glyceraldehyde-3-phosphate dehydrogenase expression (mean ± standard error of the mean [SEM]), were CuZn-SOD, 1.52 ± 0.13; Mn-SOD, 1.72 ± 0.08; EC-SOD, 0.35 ± 0.08; GSS, 2.43 ± 0.20; GSR, 2.52 ± 0.16; and CAT, 0.90 ± 0.08. The mRNA levels for CuZn-SOD were strongly correlated with GSS, GSR, Mn-SOD, and EC-SOD. Similarly, the levels of mRNA of GSS and GSR were strongly correlated with each other and with Mn-SOD and EC-SOD.

Normal human conjunctiva expresses the antioxidant enzymes genes CuZn-SOD, Mn-SOD, EC-SOD, CAT, GSS, and GSR. The relative quantitation of these genes expressed in conjunctivas of normal eyes will allow further comparisons in pathological circumstances. Knowledge of correlated gene expression will provide a better understanding of the antioxidant balance in the ocular surface.