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Cholesterol oxides, signal transduction and cell dysfunction in the lens: a bizarre love triangle
Author(s) -
PEREIRA P,
FERNANDES AF,
FERREIRA J,
BRITO A,
GIRAO H
Publication year - 2008
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2008.4242.x
Subject(s) - autophagy , protein kinase b , pi3k/akt/mtor pathway , microbiology and biotechnology , wortmannin , chemistry , p38 mitogen activated protein kinases , western blot , signal transduction , mapk/erk pathway , biology , biochemistry , apoptosis , gene
Purpose Cholesterol oxides was implicated in the development of cataract. The purpose of this study is to elucidate the molecular mechanisms underlying cholesterol oxide‐induced cell dysfunction in the lens. Methods Lens epithelial cells (LEC) were incubated with 7‐ketocholesterol (7‐KC) and 25‐hydroxycholesterol (25‐OH). The effects of cholesterol oxides on cytoskeleton were evaluated by immunofluorescence microscopy. Activation of p38 MAPK and Akt was detected by Western Blot. LC3 processing was detected by Western Blot and immunofluorescence confocal microscopy and autophagy was assessed by the LC3 I/LC3 II ratio. Results Cells treated with 25‐OH show increased migration and formation of lamellipodia. These effects are reversed by inhibitors of PI3K and p38 MAPK. Consistently, 25‐OH induces activation of Akt and p38 MAPK in LEC. On the other hand, treatment of LEC with 7‐KC decreases Akt levels and up‐regulates autophagy. The increase in autophagy following treatment with 7‐KC is prevented by overexpressing a constitutive active Akt. Chemical inhibition of PI3K or overexpression of a dominant negative Akt also leads to stimulation of autophagy. Conclusion 7‐KC stimulates autophagy in LEC by promoting degradation of Akt and activation of mTOR. The two different cholesterol oxides (7‐KC, 25‐OH) have opposite effects in the regulation of Akt, resulting in increased autophagy (7‐KC) and increased cell migration (25‐OH). Accumulation of cholesterol oxides in lens may thus account for loss of cell transparency by interfering with cell migration and by deregulating autophagy in LEC. Supported by FCT grants POCI/SAU‐MMO/57216/2004 and POCI/SAU‐OBS/57772/2004.