Abstract
Purpose: :
A healthy ocular surface is essential to maintain stable visual function and ocular barrier functions. Nrf2 is a transcription factor that regulates downstream target genes encoding biological defense enzymes including antioxidant and detoxification enzymes to protect the tissues. We used the Nrf2(-/-) mice and investigated the effect of passive current tobacco smoke exposure (TSE) on the ocular surface and tear functions.
Methods: :
Ten weeks old C57/B6 wild type mice (wt) and Nrf2 (-/-) mice were used for evaluations of the tear volume, vital staining including fluorescein and Rose Begal staining. Immunohistochemistry staining and real time PCR evmployed to evaluate the presence of Muc1, Muc4 and Muc5ac glycoproteins and their mRNA expression in cornea and conjunctival tissues. Oxidative stress related tissue damage was evaluated using anti-4-hydroxy-2-nonenal (4HNE) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) antibodies.
Results: :
Nrf2 was highly expressed in cornea and conjunctival epithelium in the wt mice. There were no differences in relation to the tear functions, vital stainings and ocular surface mucin expressions before TSE between two groups. There was also no difference in tear volume between the two groups after TSE. The fluorescein and Rose Bengal staining score in Nrf2 (-/-) mice after TSE was significantly worse than wt mice (p < 0.05). Cornea and conjunctival epithelium in Nrf2(-/-) mice after TSE revealed marked staining with 4HNE and 8-OHdG antibodies. The extent of antibody stained area by oxidative stress markers in Nrf2(-/-) mice after TSE were significantly higher than wt mice (p< 0.05). The Muc1 and Muc5ac mRNA expressions in the conjunctiva of Nrf2(-/-) mice after TSE, and Muc1 and Muc4 mRNA expression in the cornea of Nrf2(-/-) mice after TSE were significantly lower than the wt mice.
Conclusions: :
Current study revealed that Nrf2 is involved in the pathogenesis of ocular surface damage after tobacco smoke exposure owing to accumulation of oxidative stress and alteration of ocular surface mucin.
Keywords: conjunctiva • cornea: surface mucins