Abstract
Purpose: :
To investigate the thioltransferase (TTase)/glutathione reductase (GR)/GSH and thioredoxin (Trx)/thioredoxin reductase (TR)/NADPH systems for protein-thiol damage repair in the human cataratous lenses.
Methods: :
Sixty-seven human cataractous lenses (57-85 yrs) were classified into cortical (16), nuclear (15), mixed (14), posterior subcapsular (2), mature (15) and hypermature (7) cataracts by the LOCSIII system, and obtained through extracapsular cataract extraction (ECCE) procedure. Lens homogenate was used for free GSH analysis and enzyme activity assays for GR, TTase, Trx and TR. Presence of these enzymes was detected by Western blot analysis using specific antibody. Seven clear lenses (49-71 yrs) were each dissected to obtain the inner cortical-nuclear region and used as controls.
Results: :
In comparison with the control, cataractous lenses of cortical, nuclear, mixed and posterior subcapsular all lost > 80% GSH with less than 20-30% activity remained in GR, TR and Trx, while over 30-60% of TTase was still active. Mature and hypermature cataracts had little or no detectable GSH with very weak activities in all these enzymes. Western blot analysis showed that Trx, TTase and GR remained in a fairly stable and detectable quantity in all the cataract types. However, the hypermature cataract lost almost all of Trx but showed much higher expression in TR and moderate amount in TTase, in comparison with the control and other cataract types.
Conclusions: :
Human cataractous lens, regardless of which type, lost both thioltransferase and thioredoxin systems to repair for the oxidative damages in protein-thiols.
Keywords: cataract • enzymes/enzyme inhibitors • oxidation/oxidative or free radical damage