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.

Contrary to the general assumption that the peroxidase activity is the main mechanism for Prdx6 antioxidant function, these results indicate that the PLA(2) activity also plays a substantial role in protecting cells against oxidant stress caused by an exogenous hydroperoxide.

No abstract

A well-functioning placenta is crucial for normal gestation and regulates the nutrient, gas, and waste exchanges between the maternal and fetal circulations and is an important endocrine organ producing hormones that regulate both the maternal and fetal physiologies during pregnancy. Placental insufficiency is implicated in spontaneous preterm birth (SPTB). We proposed that deficits in the capacity of the placenta to maintain bioenergetic and metabolic stability during pregnancy may ultimately result in SPTB. To explore our hypothesis, we performed a RNA-seq study in male and female placentas from women with SPTB (<36 weeks gestation) compared to normal pregnancies (≥38 weeks gestation) to assess the alterations in the gene expression profiles. We focused exclusively on Black women (cases and controls), who are at the highest risk of SPTB. Six hundred and seventy differentially expressed genes were identified in male SPTB placentas. Among them, 313 and 357 transcripts were increased and decreased, respectively. In contrast, only 61 differentially expressed genes were identified in female SPTB placenta. The ingenuity pathway analysis showed alterations in the genes and canonical pathways critical for regulating inflammation, oxidative stress, detoxification, mitochondrial function, energy metabolism, and the extracellular matrix. Many upstream regulators and master regulators important for nutrient-sensing and metabolism were also altered in SPTB placentas, including the PI3K complex, TGFB1/SMADs, SMARCA4, TP63, CDKN2A, BRCA1, and NFAT. The transcriptome was integrated with published human placental metabolome to assess the interactions of altered genes and metabolites. Collectively, significant and biologically relevant alterations in the transcriptome were identified in SPTB placentas with fetal sex disparities. Altered energy metabolism, mitochondrial function, inflammation, and detoxification may underly the mechanisms of placental dysfunction in SPTB.

Peroxiredoxin 6 (Prdx6) is a 1-Cys member of the peroxiredoxin superfamily that plays an important role in antioxidant defense. Glutathionylation of recombinant Prdx6 mediated by π glutathione S-transferase (GST) is required for reduction of the oxidized Cys and completion of the peroxidatic catalytic cycle in vitro. This study investigated the requirement for πGST in intact cells. Transfection with a plasmid construct expressing πGST into MCF7, a cell line that lacks endogenous πGST, significantly increased phospholipid peroxidase activity as measured in cell lysates and protected intact cells against a peroxidative stress. siRNA knockdown indicated that this increased peroxidase activity was Prdx6 dependent. Interaction between πGST and Prdx6, evaluated by the Duolink Proximity Ligation Assay, was minimal under basal conditions but increased dramatically following treatment of cells with the oxidant, tert-butyl hydroperoxide. Interaction was abolished by mutation of C47, the active site for Prdx6 peroxidase activity. Depletion of cellular GSH by treatment of cells with buthionine sulfoximine had no effect on the interaction of Prdx6 and πGST. These data are consistent with the hypothesis that oxidation of the catalytic cysteine in Prdx6 is required for its interaction with πGST and that the interaction plays an important role in regenerating the peroxidase activity of Prdx6.