Abstract

URUETA-CUELLAR, Héctor; ALBORES, Martha; AGUILAR, Raúl  and  SANCHEZ DE JIMENEZ, Estela. Protective effect of polyphenols against damage from reactive oxygen species in maize (Zea mays L.). TIP [online]. 2010, vol.13, n.1, pp.5-15. ISSN 1405-888X.

All living organisms are exposed to lethal oxidative effects from free radicals (ROS) produced in their cells from environmental or internal agents. The present research is concerned with the identification, by data base comparative genomic studies, of the maize (Zea mays L.) orthologue PTEN (Phosphatase and Tensin homolog), a relevant enzyme in maintaining the reduced state of living organisms. The maize enzyme showed to contain the characteristic PTEN active site nucleotide sequences of other eukaryotes. To corroborate PTEN sensitivity to ROS, the effect of H₂O₂ was determined on seed germination. The protective antioxidant effect of a methanolic extract from tamarind seeds (EMT), due to its polyphenol concentration, was also determined. The participation of PTEN in the PI3K-TOR maize pathway, was shown by analysis of its response to insulin, as well as to H₂O₂. Both compounds stimulated cell growth of germinating seeds, increasing [³⁵S]-methionine incorporation into de novo ribosomal protein synthesis. Furthermore, a mitogenic effect, induced by either of these compounds was made evident by the increment of [³H]-thymidine incorporation into DNA. These effects were avoided by the presence of polyphenolic antioxidants, that restored PTEN activity, as demostrated by measuring [³⁵P]-incorporation into the phosphoinositides PIP3/PIP2 (Phosphatidylinositol 3,4,5-trisphosphate/phosphatidylinositol 4,5-biphosphate) in the analyzed tissues. These results indicate that enzyme PTEN inhibition by ROS might be reversed by polyphenol compounds as those present in EMT. These results strengthen the possibility of identifying, through bioassays in plants, compounds with high polyphenol content that might be used to help on the maintenance of living organisms into a reduced state.

Keywords : antioxidant; ROS; protein kinase; PTEN; signal transduction.