Effect of age on the thioltransferase (glutaredoxin) and thioredoxin systems in the human lens.
OBJECTIVE
To investigate the effect of age on the key oxidation repair enzymes of the thioltransferase (TTase) and thioredoxin (TRx) systems in the human lens.


METHODS
Twenty-three normal human lenses (donor ages, 19-77 years) were grouped into second, third, fifth, sixth, and seventh decades and analyzed for TTase, TRx, glutathione reductase (GR), thioredoxin reductase (TR), and glyceraldehyde-3-phosphate dehydrogenase (G3PD) activities, as well as the glutathione (GSH) pool. Additionally, 19 contralateral lenses of the donor eyes were each divided into cortex and nucleus for enzyme distribution studies.


RESULTS
All the enzymes showed similar activity in the cortex and nucleus, regardless of age, but were inactivated to various extents in the older lenses. In the TTase system, both TTase and GR showed activity loss over the five decades, with 70% remaining in the seventh decade, whereas the GSH pool was depleted extensively, with only 35% left in the older lenses. In the TRx system, TRx activity was not affected as much as TR for which only 70% of the activity was found in the seventh decade compared with the second to third decades. Overall, G3PD was more sensitive to age because only 50% activity remained after the sixth decade.


CONCLUSIONS
With increasing age there is a gradual activity loss in both the TTase and the TRx systems and a lowered GSH pool. These alterations, compounded with the age-related loss in G3PD activity, may lead to redox and energy imbalance, likely contributing to a higher risk to cataract formation in the aging population.
Xing
Kui-Yi
KY
School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE 68583-0905, USA.
Lou
Marjorie F
MF
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002386:Cataract / Q000201:enzymology; D054477:Glutaredoxins / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D050536:Glycerol-3-Phosphate Dehydrogenase (NAD+) / Q000378:metabolism; D006801:Humans; D007904:Lens Cortex, Crystalline / Q000378:metabolism; D007907:Lens Nucleus, Crystalline / Q000378:metabolism; D007908:Lens, Crystalline / Q000378:metabolism*; D008875:Middle Aged; D012307:Risk Factors; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism*; D055815:Young Adult
C516005:GLRX protein, human; D054477:Glutaredoxins; D013879:Thioredoxins; D050536:Glycerol-3-Phosphate Dehydrogenase (NAD+); D005980:Glutathione Reductase; D013880:Thioredoxin-Disulfide Reductase; D005978:Glutathione