Peroxiredoxin 6 (Prdx6), a bifunctional enzyme with glutathione peroxidase and phospholipase A2 (PLA 2 ) activities, participates in the activation of NADPH oxidase 2 (NOX2) in neutrophils, but the mechanism for this effect is not known. We now demonstrate that Prdx6 is required for agonist-induced NOX2 activation in pulmonary microvascular endothelial cells (PMVEC) and that the effect requires the PLA 2 activity of Prdx6. Generation of reactive oxygen species (ROS) in response to angiotensin II (Ang II) or phorbol 12-myristate 13-acetate was markedly reduced in perfused lungs and isolated PMVEC from Prdx6 null mice. Rac1 and p47phox , cytosolic components of NOX2, translocated to the endothelial cell membrane after Ang II treatment in wild-type but not Prdx6 null PMVEC. MJ33, an inhibitor of Prdx6 PLA 2 activity, blocked agonist-induced PLA 2 activity and ROS generation in PMVEC by >80%, whereas inhibitors of other PLA 2 s were ineffective. Transfection of Prx6 null cells with wild-type and C47S mutant Prdx6, but not with mutants of the PLA 2 active site (S32A, H26A, and D140A), "rescued" Ang II-induced PLA 2 activity and ROS generation. Ang II treatment of wild-type cells resulted in phosphorylation of Prdx6 and its subsequent translocation from the cytosol to the cell membrane. Phosphorylation as well as PLA 2 activity and ROS generation were markedly reduced by the MAPK inhibitor, U0126. Thus, agonist-induced MAPK activation leads to Prdx6 phosphorylation and translocation to the cell membrane, where its PLA 2 activity facilitates assembly of the NOX2 complex and activation of the oxidase.

Oxidant stress induces constitutive calcium entry by tacking glutathiones onto the Orai CRAC channel activator STIM1.

Although radiation-induced bystander effects have been well described over the past decade, the mechanisms of the signaling processes involved in the bystander phenomenon remain unclear. In the present study, using the Columbia University charged particle microbeam, we found that mitochondrial DNA-depleted human skin fibroblasts (R o ) showed a higher bystander mutagenic response in confluent monolayers when a fraction of the same population were irradiated with lethal doses compared with their parental mitochondrial-functional cells (R + ). However, using mixed cultures of R o and R + cells and targeting only one population of cells with a lethal dose of A-particles, a decreased bystander mutagenesis was uniformly found in nonirradiated bystander cells of both cell types, indicating that signals from one cell type can modulate expression of bystander response in another cell type. In addition, we found that Bay 11-7082, a pharmacologic inhibitor of nuclear factor-KB (NF-KB) activation, and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a scavenger of nitric oxide (NO), significantly decreased the mutation frequency in both bystander R o and R + cells. Furthermore, we found that NF-KB activity and its dependent proteins, cyclooxygenase-2 (COX-2) and inducible NO synthase (iNOS), were lower in bystander R o cells when compared with their R + counterparts. Our results indicated that mitochondria play an important role in the regulation of radiation-induced bystander effects and that mitochondriadependent NF-KB/iNOS/NO and NF-KB/COX-2/prostaglandin E2 signaling pathways are important to the process. [Cancer Res 2008;68(7):2233-40]

Fetal and subsequent early postnatal iron deficiency causes persistent impairments in cognitive and affective behaviors despite prompt postnatal iron repletion. The long-term cognitive impacts are accompanied by persistent downregulation of brain-derived neurotrophic factor (BDNF), a factor critical for hippocampal plasticity across the life span. This study determined whether early-life iron deficiency epigenetically modifies the Bdnf locus and whether dietary choline supplementation during late gestation reverses these modifications. DNA methylation and histone modifications were assessed at the Bdnf-IV promoter in the hippocampus of rats [at postnatal day (PND) 65] that were iron-deficient (ID) during the fetal-neonatal period. Iron deficiency was induced in rat pups by providing pregnant and nursing dams an ID diet (4 mg/kg Fe) from gestational day (G) 2 through PND7, after which iron deficiency was treated with an iron-sufficient (IS) diet (200 mg/kg Fe). This paradigm resulted in about 60% hippocampal iron loss on PND15 with complete recovery by PND65. For choline supplementation, pregnant rat dams were given dietary choline (5 g/kg) from G11 through G18. DNA methylation was determined by quantitative sequencing of bisulfite-treated DNA, revealing a small alteration at the Bdnf-IV promoter. Chromatin immunoprecipitation analysis showed increased HDAC1 binding accompanied by reduced binding of RNA polymerase II and USF1 at the Bdnf-IV promoter in formerly ID rats. These changes were correlated with altered histone methylations. Prenatal choline supplementation reverses these epigenetic modifications. Collectively, the findings identify epigenetic modifications as a potential mechanism to explicate the long-term repression of Bdnf following fetal and early postnatal iron deficiency.