Neuroprotective effects of PrxI over‐expression in an in vitro human Alzheimer's disease model

Peroxiredoxins are ubiquitous proteins that recently attracted major interests in view of the strict correlation observed in several cell lines and/or tissues between different levels of their expression and the increased capacity of cells to survive in different pathophysiological conditions. They are recently considered as the most important enzymes regulating the concentration of hydroperoxides inside the cells. Most of neurodisorders such as Parkinson, Huntington, Alzheimer's diseases, and ischemic injury are characterized by conditions of oxidative stress inside cells. In these pathophysiological conditions, a strict correlation between cell survival and Prx expression has been found. In CNS all the Prx isoforms are present though with different expression pattern depending on cell phenotype. Interestingly, neurons treated with amyloid beta peptide (Aβ), showed an overexpression of PrxI. In this study, the neuroprotective effect of PrxI after Aβ exposure and the underlying mechanisms by which PrxI expression counteracts cell death was investigated in a well established human AD in vitro model. Taking advantage on cells transfected by a construct where human PrxI is fused with a Green fluorescent protein (GFP) at the C‐terminus, we report some events at the basis of cell survival after Aβ injury, suggesting possible new signal cascades dealing with the antiapoptotic effect of PrxI. The results obtained indicated a protective role for PrxI in counteracting Aβ injury by increasing cell viability, preserving neurites, and decreasing cell death. J. Cell. Biochem. 114: 708–715, 2013. © 2012 Wiley Periodicals, Inc.     

Spodoptera frugiperda FKBP‐46 is a consensus p53 motif binding protein

p53 protein, the central molecule of the apoptosis pathway, is mutated in 50% of the human cancers. Of late, p53 homologues have been identified from different invertebrates including Drosophila melanogaster, Caenorhabditis elegans, Squid, and Clams. We report the identification of a p53‐like protein in Spodoptera frugiperda (Sf9) insect cells, which is activated during oxidative stress, caused by exposure to UV‐B or H₂O₂, and binds to p53 consensus DNA binding motifs as well as other p53 cognate motifs. Sf9 p53 motif‐binding protein is similar to murine and Drosophila p53 in terms of molecular size, which is around 50–60 kDa, as evident from UV cross‐linking, and displays DNA binding characteristics similar to both insect and vertebrate p53 as seen from electrophoretic mobility shift assays. The N‐terminal sequencing of the purified Sf9 p53 motif‐binding protein reveals extensive homology to the pro‐apoptotic FK‐506 binding protein (FKBP‐46), earlier identified in Sf9 cells as a factor which interacts with murine casein kinase. FKBP, an evolutionarily conserved protein of mammalian origin functions as a pro‐apoptotic factor. Identification of FKBP‐46 as a novel p53 motif‐binding protein in insect cells adds a new facet to our understanding of the mechanisms of apoptosis under oxidative stress in the absence of a typical p53 homologue. J. Cell. Biochem. 114: 899–907, 2013. © 2012 Wiley Periodicals, Inc.     

Role of eosinophil peroxidase in the origins of protein oxidation in asthma

Abstract

Eosinophils are uniquely endowed with an arsenal of enzymes that enable them to generate an array of reactive oxidants and diffusible radical species. The formidable arsenal at their disposal likely evolved because of the central role these phagocytes play in combating invading helminths and other large metazoan pathogens. Although these leukocytes constitute an essential component of the effector limb of host defenses, they also are implicated in contributing to inflammatory tissue injury. The growing prevalence and severity of asthma, a respiratory disease characterized by recruitment and activation of eosinophils in the airways of affected individuals, has focused research efforts on elaborating the many potential mechanisms through which eosinophils may contribute to tissue injury and oxidative modification of biological targets in asthma. Eosinophil activation is strongly suspected as playing a contributory role in the pathogenesis of asthma. Accordingly, an understanding of the basic chemical pathways available to the leukocytes for generating specific reactive oxidants and diffusible radical species in vivo is required. In the following review, recent progress in the elaboration of specific mechanisms through which eosinophils generate oxidants and other reactive species are discussed. The potential contributions of these intermediates to modification of biological targets during asthma are described. Particular emphasis is placed upon the secreted hemoprotein eosinophil peroxidase (EPO), a central participant in generation of reactive oxidants and diffusible radical species by the phagocytes.     

Oxidative stress and apoptosis in homocystinuria patients with genetic remethylation defects

Oxidative stress has been described as a putative disease mechanism in pathologies associated with an elevation of homocysteine. An increased reactive oxygen species (ROS) production and apoptosis rate have been associated with several disorders of cobalamin metabolism, particularly with methylmalonic aciduria (MMA) combined with homocystinuria cblC type. In this work, we have evaluated several parameters related to oxidative stress and apoptosis in fibroblasts from patients with homocystinuria due to defects in the MTR, MTRR, and MTHFR genes involved in the remethylation pathway of homocysteine. We have also evaluated these processes by knocking down the MTRR gene in cellular models, and complementation by transducing the wild‐type gene in cblE mutant fibroblasts. All cell lines showed a significant increase in ROS content and in MnSOD expression level, and also a higher rate of apoptosis with similar levels to the ones in cblC fibroblasts. The amount of the active phosphorylated forms of p38 and JNK stress‐kinases was also increased. ROS content and apoptosis rate increased in control fibroblasts and in a glioblastoma cell line by shRNA‐mediated silencing of MTRR gene expression. In contrast, wild‐type MTRR gene corrected mutant cell lines showed a decrease in ROS and apoptosis levels. To the best of our knowledge, this study provides the first evidence that an impaired remethylation capacity due to low MTRR and MTR activity might be partially responsible for stress response. J. Cell. Biochem. 114: 183–191, 2012. © 2012 Wiley Periodicals, Inc.