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J. Zhou, X. Duan; P38 MAP Kinase Mediates Apoptosis of Lens Cells in Formation of Galactose Cataract. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2133.
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There is no direct evidence to demonstrate that p38 activation involves in apoptosis in formation of galactose cataract, although it has shown that activation of p38 and apoptosis of lens epithelial cells were found in galactose treated lenses both in vitro and in vivo. The goal of this study is to determine the signaling pathway of apoptosis mediated by p38 in development of galactose cataract in vitro.
The cataract model was induced by 30mM/L galactose in 10-day chicken embryonic lenses cultured in Medium 199 with 10%FBS for ten days, treated with or without inhibitor of p38, SB203580. We observed and photographed the cultured lenses daily, and the degree of opacification was quantified by using imagine software. Phospo-p38 in the lens epithelium of cultured lenses was determined by western blot assay. Histomorphological changes of the cultured lenses were observed after immunostaining with WGA for cellular membrane and DAPI for cellular nucleus on the frozen sections. Apoptotic cells were detected by TUNEL assay, and the activity of caspase-3 of lens epithelial cells in the cultured lens was measured by CaspACETM Assay System.
Activation of p38 was found in the cultured lens treated with 30mM/L galactose during the 10-day-culture period, and it was inhibited by SB203580. The cultured lens developed opacification at the periphery cortex, and the degree of opacification increased with time during culture period. Lenses treated with SB203580 developed the similar phenotype of cortical opacity, but the area of opacification was attenuated. By immunostaining with WGA and DAPI, we found the architecture of lens had abnormalities in the shape and organization of the lens fiber cells in equatorial zones and underneath lens epithelium zone. Culturing the lenses in presence of SB203580 prevented these aberrations as well as development of lens opacity. In the section of galactose cataract lenses, the percentage of apoptotic cells was 1.7%, 4.5% and 12% at cultured day 2, 5 and 10, but in SB203580-treated lenses it was decreased dramatically to 0.7%, 1.5% and 1.4%, respectively. Further more, the activity of caspase-3 in the lens epithelium of galactose cataracts increased to 8.5,19.5 and 41.9 folds of E10 lens at culture day 2, 5 and 10, while in SB203580-treated lenses, caspase-3 activity was inhibited to 3,7.8 and 26.9 folds of E10 lens, respectively.
Activation of p38 may involve in formation of galactose cataract by mediating the signaling pathway of apoptosis in lens epithelial cells. Inhibition of p38 activity can inhibit activity of caspase-3 and prevent the lens epithelial cells from apoptosis, by which attenuates formation of cataract.Keywords: p38, apoptosis, cataract, galactose
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