Hawse JR, Cumming JR, Oppermann B, Sheets NL, Reddy VN, Kantorow M. Activation of metallothioneins and alpha-crystallin/sHSPs in human lens epithelial cells by specific metals and the metal content of aging clear human lenses.
Invest Ophthalmol Vis Sci 2003;
44:672-9. [PMID:
12556398 PMCID:
PMC2825746 DOI:
10.1167/iovs.02-0018]
[Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE
To identify those metallothionein and alpha-crystallin/small heat-shock genes induced by toxic metals in human lens cells and to evaluate the levels of these metals between young and aged human lenses.
METHODS
Human SRA01/04 and primary human lens epithelial cells were cultured and exposed to Cd(2+), Cu(2+), and Zn(2+). The levels of lens metallothioneins (Ig, If, Ih, Ie, and IIa) and alpha-crystallin/small heat-shock (alphaA-crystallin, alphaB-crystallin, and HSP27) genes were analyzed by semiquantitative and quantitative competitive RT-PCR. The content of aluminum, cadmium, calcium, chromium, copper, iron, lead, magnesium, manganese, nickel, potassium, sodium, and zinc in young (mean, 32.8 years), middle-aged (mean, 52.3 years), and old (mean, 70.5 years) human lenses was analyzed by inductively coupled plasma-emission spectroscopy.
RESULTS
Lens metallothioneins (Ig, If, Ih, Ie, and IIa) and alpha-crystallin/small heat-shock genes (alphaA-crystallin, alphaB-crystallin, and HSP27) were differentially induced by specific metals in SRA01/04 human lens epithelial cells. Cd(2+) and Zn(2+), but not Cu(2+), induced the metallothioneins, whereas Cd(2+) and Cu(2+), but not Zn(2+), induced alphaB-crystallin and HSP27. alphaA-crystallin was induced by Cu(2+) only. Similar responses of the metallothionein IIa gene were detected in identically treated primary human lens epithelial cells. Cd(2+) and Zn(2+) induced metallothionein IIa to five times higher levels than metallothionein Ig. Of 13 different metals, only iron was altered, exhibiting an 81% decrease in old versus young lenses.
CONCLUSIONS
Induction of metallothioneins and alpha-crystallin/small heat shock proteins by different metals indicates the presence of metal-specific lens regulatory pathways that are likely to be involved in protection against metal-associated stresses.
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