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M. F. Lou, N. Liyanage, J. Hon, K. Xing; Distribution of Thioredoxin and Thioredoxin Binding Protein-2 in Human Eye Tissues. Invest. Ophthalmol. Vis. Sci. 2010;51(13):712.
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Thioredoxin (Trx) is a multifunctional redox regulator present ubiquitously in all forms of life. Recently, a specific Trx binding protein, thioredoxin binding protein-2 (TBP-2), is found and appears to control the bioavailability of intracellular Trx in some cell types. However, little is known on the distribution and relationship of Trx and TBP-2 in the eye. This study is to examine the expressions of Trx and TBP-2 under physiological and pathological conditions, and the effect of aging in human eye tissues.
Human donor eyes at age 31, 53, 68, 84, 89 yrs were each dissected into conjunctiva, cornea, ciliary body, iris, lens, retina and optical nerve. Each tissue was homogenized in lysis buffer and used for Western blot analysis with specific antibody against Trx or TBP-2. The records of clinical history and cause of death from each donor were used for reference.
Trx and TBP-2 were both present in all the eye tissues examined. However there was a general trend of higher levels of Trx in the anterior segment than the posterior segment of the eye, in particular, the cornea and cilliary body. Trx was expressed more in optical nerve than the retina. In all tissues, the TBP-2 level was lower than Trx except in conjunctiva. Age seemed to show some variation of expression of these two proteins but there was a trend of higher Trx/TBP-2 ratio in the young than that of the old eye tissues. Interestingly, there was a clear inverse relationship betweenTBP-2 and Trx, i.e. when a tissue contained high Trx, TBP-2 was low while a tissue contained low Trx, TBP-2 was high. Trx and TBP-2 protein levels were elevated in many parts of the eye tissues of donor with leukemia, or multiple myeloma or diabetes mellitus.
The expression and distribution of Trx and TBP-2 in eye tissues were studies for the first time. The presence of higher Trx level in the anterior segment is consistent with the risk of higher oxidative stress in this region. Several chronic diseases significantly altered the Trx and TBP-2 protein levels in human eye tissues.
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