Exploration of Molecular Factors Impairing Superoxide Dismutase Isoforms Activity in Human Senile Cataractous Lenses

PURPOSE. To explore different molecular factors impairing the activities of superoxide dismutase (SOD) isoforms in senile cataractous lenses. METHODS. Enzyme activity of SOD isoforms, levels of their corresponding cofactors copper (Cu), manganese (Mn), zinc (Zn), and expression of mRNA transcripts and proteins were determined in the lenses of human subjects with and without cataract. DNA from lens epithelium (LE) and peripheral blood was isolated. Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) followed by sequencing was carried out to screen somatic mutations. The impact of intronic insertion/deletion (INDEL) variations on the splicing process and on the resultant transcript was evaluated. Genotyping of IVS4þ42delG polymorphism of SOD1 gene was done by PCR-restriction fragment length polymorphism (RFLP). RESULTS. A significant decrease in Cu/Zn-and Mn-SOD activity (P < 0.001) and in Cu/Zn-SOD transcript (P < 0.001) and its protein (P < 0.05) were found in cataractous lenses. No significant change in the level of copper (P ¼ 0.36) and an increase in the level of manganese (P ¼ 0.01) and zinc (P ¼ 0.02) were observed in cataractous lenses. A significant positive correlation between the level of Cu/Zn-SOD activity and the levels of Cu (P ¼ 0.003) and Zn (P ¼ 0.005) was found in the cataractous lenses. DNA sequencing revealed three intronic INDEL variations in exon4 of SOD1 gene. Splice-junction analysis showed the potential of IVS4þ42delG in creating a new cryptic acceptor site. If it is involved in alternate splicing, it could result in generation of SOD1 mRNA transcripts lacking exon4 region. Transcript analysis revealed the presence of complete SOD1 mRNA transcripts. Genotyping revealed the presence of IVS4þ42delG polymorphism in all subjects. CONCLUSIONS. The decrease in the activity of SOD1 isoform in cataractous lenses was associated with the decreased level of mRNA transcripts and their protein expression and was not associated with either modulation in the level of enzyme cofactors or with INDEL variations

Estrogen mediated protection of cytoskeleton against oxidative stress

Background & objectives: Cytoskeletal proteins are deregulated during oxidative stress and cataract formation. However, estrogen which protects against cataract formation and harmful effects of oxidative stress has not been tested on the cytoskeleton of lens epithelial cells (LECs). The current study was undertaken to assess if the protection rendered to LECs by estrogen was mediated by preserving the cytoskeletal proteins. Methods: Oxidative stress was induced by 50 μM of H 2 O 2 in cultured goat LECs (gLECs) and effect of 1 μM 17β-estradiol (E 2 ) was tested. After treatment, morphological analysis of cells was carried out using haematoxylin-eosin staining and cell density was also quantified. Cell viability was determined using Hoechst (Ho), YO-Pro (YP) and propidium iodide (PI). F-actin and vimentin were localized using phalloidin and anti-vimentin antibody, respectively, and viewed under fluorescence microscopy. Vimentin was further analysed at protein level by Western blotting. Results: H 2 O 2 led to increased condensation of nucleus, cell death and apoptosis but these were prevented with pre- and co-treatment of E 2 with increase in cell viability (P<0.001). E 2 also prevented H 2 O 2 mediated depolymerization of cytoskeleton but was not able to reverse the changes when given after induction of oxidative stress. Interpretation & conclusions: Our findings showed that E 2 helped in preventing deteriorating effect of H 2 O 2 , inhibited cell death, apoptosis and depolymerisation of cytoskeletal proteins in LECs. However, the exact mechanism by which estrogen renders this protection to cytoskeleton of lens epithelial cells remains to be determined