Decreased chaperone activity of alpha-crystallin in selenite cataract may result from selenite-induced aggregation.
OBJECTIVE
To investigate the role of chaperone activity of alpha-crystallin in selenite-induced cataract formation.


METHODS
Selenite cataract was induced in Sprague-Dawley rats by five subcutaneous injections of sodium selenite over a 20-day period starting at 8-10 days postpartum. alpha-Crystallin was separated from the rat lenses by size-exclusion chromatography. Bovine alpha(L)-crystallin and beta(L)-crystallin were isolated for studies in vitro, and for the chaperone assays. The protective effects of both alpha(H)- and alpha(L)-crystallin were measured spectrophotometrically in four different assay procedures including the thermally induced aggregation of catalase and beta(L)-crystallin, and the fructation- and heat-induced inactivation of catalase. The bovine alpha(L)-crystallin was incubated with different concentrations of sodium selenite for 72 h and then its chaperone activity against heat-induced beta(L)-crystallin aggregation was assayed. The aggregation of selenite-treated alpha(L)-crystallin was analysed by molecular sieve high-performance liquid chromatography (HPLC).


RESULTS
The protection of alpha(H)-crystallin was less than that of alpha(L)-crystallin in both normal and cataractous lenses. The chaperone activities of both alpha(H)- and alpha(L)-crystallin in selenite cataract were decreased compared with normal lenses. The protection provided by both alpha(H)-crystallin and alpha(L)-crystallin against the thermal aggregation of catalase was much greater than their protection against thermally and chemically induced inactivation. HPLC analysis demonstrated aggregation of alpha-crystallin by sodium selenite after 24 h incubation in a dose-dependent fashion.


CONCLUSIONS
The chaperone activity of alpha-crystallin presented parallel patterns of activity with different methods, further supporting the view that the different assays measure essentially the same property. The decreased chaperone activity of alpha-crystallin in selenite cataract may result from selenite-induced aggregation.
Yan
H
H
Department of Ophthalmology, Tangdu Hospital, The Fourth Military Medical University, Xi'an, China.
Harding
J J
JJ
Hui
Y N
YN
Li
M Y
MY
D000818:Animals; D002386:Cataract / Q000139:chemically induced / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D007908:Lens, Crystalline / Q000378:metabolism; D018832:Molecular Chaperones / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018038:Sodium Selenite; D038201:alpha-Crystallins / Q000378:metabolism*
D018832:Molecular Chaperones; D038201:alpha-Crystallins; D018038:Sodium Selenite