H2O2 in the Induction of NF-κB-Dependent Selective Gene Expression

Colloidal Particles in Tuna Head Soup: Chemical Localization, Structural Change, and Antioxidant Property

In this work, chemical localization, structural changes, and antioxidant properties of tuna colloidal particles (TCPs) in boiling tuna head soup were examined. The results demonstrated that TCPs might be core–shell colloidal spherical structures. The hydrophobic core consisted of triglycerides and chloride ions. The hydrophilic shell layer consisted of chloride ions, sodium ions, phospholipids, protein, and glycosyl molecules. Coalescence of TCPs occurred during the boiling process, and water may enter the hydrophobic core of TCPs after the boiling time of 60 min. TCPs had excellent antioxidant properties against H₂O₂-induced human umbilical vein endothelial cell injury. It might be resulted from that TCPs could decrease cell apoptosis proportion and downregulate mRNA levels of endoplasmic reticulum-bounded chaperone protein glucose-related protein (GRP78), C/EBP homologous protein (CHOP), and activating transcription factor-4 (ATF4). This work can provide useful basic information to understand the colloidal system in foods, especially in soup. In addition, it may also promote the potential high-value-added utilization of aquatic by-products.

Endothelial dysfunction in neuroprogressive disorders-causes and suggested treatments

BACKGROUND

Potential routes whereby systemic inflammation, oxidative stress and mitochondrial dysfunction may drive the development of endothelial dysfunction and atherosclerosis, even in an environment of low cholesterol, are examined.

MAIN TEXT

Key molecular players involved in the regulation of endothelial cell function are described, including PECAM-1, VE-cadherin, VEGFRs, SFK, Rho GEF TRIO, RAC-1, ITAM, SHP-2, MAPK/ERK, STAT-3, NF-κB, PI3K/AKT, eNOS, nitric oxide, miRNAs, KLF-4 and KLF-2. The key roles of platelet activation, xanthene oxidase and myeloperoxidase in the genesis of endothelial cell dysfunction and activation are detailed. The following roles of circulating reactive oxygen species (ROS), reactive nitrogen species and pro-inflammatory cytokines in the development of endothelial cell dysfunction are then described: paracrine signalling by circulating hydrogen peroxide, inhibition of eNOS and increased levels of mitochondrial ROS, including compromised mitochondrial dynamics, loss of calcium ion homeostasis and inactivation of SIRT-1-mediated signalling pathways. Next, loss of cellular redox homeostasis is considered, including further aspects of the roles of hydrogen peroxide signalling, the pathological consequences of elevated NF-κB, compromised S-nitrosylation and the development of hypernitrosylation and increased transcription of atherogenic miRNAs. These molecular aspects are then applied to neuroprogressive disorders by considering the following potential generators of endothelial dysfunction and activation in major depressive disorder, bipolar disorder and schizophrenia: NF-κB; platelet activation; atherogenic miRs; myeloperoxidase; xanthene oxidase and uric acid; and inflammation, oxidative stress, nitrosative stress and mitochondrial dysfunction.

CONCLUSIONS

Finally, on the basis of the above molecular mechanisms, details are given of potential treatment options for mitigating endothelial cell dysfunction and activation in neuroprogressive disorders.

Hydrogen peroxide in neutrophil inflammation: Lesson from the zebrafish

The zebrafish has become an excellent model for the study of inflammation and immunity. Its unique advantages for in vivo imaging and gene and drug screening have allowed the visualization of dual oxidase 1 (Duox1)-derived hydrogen peroxide (H₂O₂) tissue gradients and its crosstalk with neutrophil infiltration to inflamed tissue. Thus, it has been shown that H₂O₂ directly recruits neutrophils via the Src-family tyrosine kinase Lyn and indirectly by the activation of several signaling pathways involved in inflammation, such as nuclear factor κB (NF-κB), mitogen activated kinases and the transcription factor AP1. In addition, this model has also unmasked the unexpected ability of H₂O₂ to induce the expression of the gene encoding the key neutrophil chemoattractant CXC chemokine ligand 8 by facilitating the accessibility of transcription factors to its promoter through histone covalent modifications. Finally, zebrafish models of psoriasis have shown that a H₂O₂/NF-κB/Duox1 positive feedback inflammatory loop operates in this chronic inflammatory disorder and that pharmacological inhibition of Duox1, but not of downstream mediators, inhibits inflammation and restores epithelial homeostasis. Therefore, these results have pointed out DUOX1 and H₂O₂ as therapeutic targets for the treatment of skin inflammatory disorders, such as psoriasis.

Neural precursor cell-expressed, developmentally down-regulated 4 (NEDD4) regulates hydrogen peroxide-induced cell proliferation and death through inhibition of Hippo signaling

E3 ubiquitin ligases are involved in the regulation of oxidative stress-induced cell death. In this study, we investigated the role of neural precursor cell-expressed, developmentally down-regulated protein 4 (NEDD4) in regulation of hydrogen peroxide (H₂O₂)-induced cell proliferation and apoptosis in human bone marrow-derived stem cells (hBMSCs). Cell proliferation was increased in low doses of H₂O₂ (10^-4 to 10^-2 μM), whereas sublethal concentrations of H₂O₂ (>200 μM) induced apoptosis. A chromatin immunoprecipitation assay identified that recruitment of NF-κB onto the promoter region of NEDD4 mediated H₂O₂-induced NEDD4 expression. The increase of NEDD4 expression by H₂O₂ induced translocation of yes-associated protein (YAP) into the nucleus by decreasing the stability of large tumor suppressor kinase (LATS). Thus, the phosphorylation of serine 127 residue of YAP by LATS upstream kinase is decreased and thereby increased the transcriptional activity of YAP. The mRNA expression levels of catalase and manganese superoxide dismutase, which are well-known targets of YAP, were increased by H₂O₂ treatment but down-regulated by NEDD4 silencing using a specific small interfering RNA targeting NEDD4 (siNEDD4). H₂O₂-induced scavenging capacity of reactive oxygen species was also decreased by siNEDD4 in hBMSCs. Finally, hBMSC differentiation into osteoblast was decreased by siNEDD4 but reverted by reintroduction of the S127A mutant construction of YAP. Taken together, these results indicate that NEDD4 regulates H₂O₂-induced alteration of cell status through regulation of the Hippo signaling pathway.-Jeon, S.-A., Kim, D. W., Cho, J.-Y. Neural precursor cell-expressed, developmentally down-regulated 4 (NEDD4) regulates hydrogen peroxide-induced cell proliferation and death through inhibition of Hippo signaling.

A novel mechanism of Gamma-aminobutyric acid (GABA) protecting human umbilical vein endothelial cells (HUVECs) against H2O2-induced oxidative injury

Vascular endothelial cell damage is related to many vascular diseases, including cardiovascular disease (CVD). Reactive oxygen species (ROS) play a vital role in the pathogenesis of many cardiovascular diseases. Herein, H₂O₂-induced human umbilical vein endothelial cell (HUVEC) injury model was used to explore the mechanisms involved in the pathogenesis of ROS-induced oxidative stress and cell dysfunction. Gamma-aminobutyric acid (GABA), a naturally occurring four-carbon non-protein amino acid, has antioxidant activity and anti-inflammatory action. In the present study, we demonstrated that GABA could scavenge free radicals including DPPH and ABTS, reverse H₂O₂-induced suppression on HUVEC proliferation, HUVEC apoptosis and ROS formation via p65 signaling. Interestingly, GABA treatment alone did not cause significant changes in p65 phosphorylation, suggesting that GABA will not cause imbalance in NF-κB signaling and ROS formation without oxidative stress. Moreover, GABA also modulated Keap1-Nrf2 and Notch signaling pathways upon H₂O₂ stimulation, suggesting that GABA may exert its effect via multi mechanisms. In conclusion, the present study demonstrated that GABA inhibits H₂O₂-induced oxidative stress in HUVECs via inhibiting ROS-induced NF-κB and Caspase 3 pathway activation. GABA may, therefore, have potential as a pharmacological agent in the prevention or treatment of oxidative injury-related cardiovascular disease.

Peroxidase-Mimicking Nanoassembly Mitigates Lipopolysaccharide-Induced Endotoxemia and Cognitive Damage in the Brain by Impeding Inflammatory Signaling in Macrophages

Oxidative stress during sepsis pathogenesis remains the most-important factor creating imbalance and dysregulation in immune-cell function, usually observed following initial infection. Hydrogen peroxide (H₂O₂), a potentially toxic reactive oxygen species (ROS), is excessively produced by pro-inflammatory immune cells during the initial phases of sepsis and plays a dominant role in regulating the pathways associated with systemic inflammatory immune activation. In the present study, we constructed a peroxide scavenger mannosylated polymeric albumin manganese dioxide (mSPAM) nanoassembly to catalyze the decomposition of H₂O₂ responsible for the hyper-activation of pro-inflammatory immune cells. In a detailed manner, we investigated the role of mSPAM nanoassembly in modulating the expression and secretion of pro-inflammatory markers elevated in bacterial lipopolysaccharide (LPS)-mediated endotoxemia during sepsis. Through a facile one-step solution-phase approach, hydrophilic bovine serum albumin reduced manganese dioxide (BM) nanoparticles were synthesized and subsequently self-assembled with cationic mannosylated disulfide cross-linked polyethylenimine (mSP) to formulate mSPAM nanoassembly. In particular, we observed that the highly stable mSPAM nanoassembly suppressed HIF1α expression by scavenging H₂O₂ in LPS-induced macrophage cells. Initial investigation revealed that a significant reduction of free radicals by the treatment of mSPAM nanoassembly has reduced the infiltration of neutrophils and other leukocytes in a local endotoxemia animal model. Furthermore, therapeutic studies in a systemic endotoxemia model demonstrated that mSPAM treatment reduced TNF-α and IL-6 inflammatory cytokines in serum, in turn circumventing organ damage done by the inflammatory macrophages. Interestingly, we also observed that the reduction of these inflammatory cytokines by mSPAM nanoassembly further prevented IBA-1 immuno-positive microglial cell activation in the brain and consequently improved the cognitive function of the animals. Altogether, the administration of mSPAM nanoassembly scavenged H₂O₂ and suppressed HIF1α expression in LPS-stimulated macrophages and thereby inhibited the progression of local and systemic inflammation as well as neuroinflammation in an LPS-induced endotoxemia model. This mSPAM nanoassembly system could serve as a potent anti-inflammatory agent, and we further anticipate its successful application in treating various inflammation-related diseases.

Antiinflammatory and antioxidant effects of H2O2 generated by natural sources in Il1β-treated human endothelial cells

Specific reactive oxygen species (ROS) from different sources, might lead to different and even opposite, cellular effects. We studied the production of specific ROS resulting from the exposure of human umbilical veins endothelial cells (HUVEC) to H2O2 derived from the natural antioxidant epigallocathechin gallate (EGCG) or from the exposure to IL-1β using a fluorogenic probe and flow cytometry, and evaluated by western blot analysis and immunocytochemistry the associated expression of transcription factors sensitive to both inflammatory and oxidative stress, such as NF-κB and Nrf2, and some downstream activated genes such as cyclooxygenase-2 (COX-2) and hemeoxygenase 1 (HO-1). The results obtained showed that exogenously-generated H2O2 induce anti-inflammatory and antioxidant effects in HUVECs counteracting the pro-inflammatory and pro-oxidant effect of IL-1β related to the production of superoxide anions. The underlying mechanisms resulting from the extracellular production of H2O2, include (1) Nrf2 nuclear translocation and the enhanced expression of antioxidant enzymes such as HO-1, and (2) the previously unreported inhibition of NF-κB and COX-2 expression. Overall, these findings provide evidence that the production of specific reactive oxygen species finely tunes endothelial cell function and might be relevant for the reappraisal of the effects of exogenous antioxidants in the context of cardiovascular diseases.

Design and synthesis of novel xyloketal derivatives and their protective activities against H2O2-induced HUVEC injury

In this work, we designed and synthesized a series of amide derivatives (1–13), benzoxazine derivatives (16–28) and amino derivatives (29–30) from xyloketal B. All 28 new derivatives and seven known compounds (14, 15, 31–35) were evaluated for their protection against H₂O₂-induced HUVEC injury. 23 and 24 exhibited more potential protective activities than other derivatives; and the EC₅₀ values of them and the leading compound 31 (xyloketal B) were 5.10, 3.59 and 15.97 μM, respectively. Meanwhile, a comparative molecular similarity indices analysis (CoMSIA) was constructed to explain the structural activity relationship of these xyloketal derivatives. This 3D QSAR model from CoMSIA suggested that the derived model exhibited good predictive ability in the external test-set validation. Derivative 24 fit well with the COMSIA map, therefore it possessed the highest activity of all compounds. Compounds 23, 24 and 31 (xyloketal B) were further to examine in the JC-1 mitochondrial membrane potential (MMP) assay of HUVECs using flow cytometry (FCM). The result indicated that 23 and 24 significantly inhibited H₂O₂-induced decrease of the cell mitochondrial membrane potential (ΔΨm) at 25 μM. Collectively, the protective effects of xyloketals on H₂O₂-induced endothelial cells may be generated from oxidation action by restraining ROS and reducing the MMP.

Estimation of kinetic parameters related to biochemical interactions between hydrogen peroxide and signal transduction proteins

The lack of kinetic data concerning the biological effects of reactive oxygen species is slowing down the development of the field of redox signaling. Herein, we deduced and applied equations to estimate kinetic parameters from typical redox signaling experiments. H2O2-sensing mediated by the oxidation of a protein target and the switch-off of this sensor, by being converted back to its reduced form, are the two processes for which kinetic parameters are determined. The experimental data required to apply the equations deduced is the fraction of the H2O2 sensor protein in the reduced or in the oxidized state measured in intact cells or living tissues after exposure to either endogenous or added H2O2. Either non-linear fittings that do not need transformation of the experimental data or linearized plots in which deviations from the equations are easily observed can be used. The equations were shown to be valid by fitting to them virtual time courses simulated with a kinetic model. The good agreement between the kinetic parameters estimated in these fittings and those used to simulate the virtual time courses supported the accuracy of the kinetic equations deduced. Finally, equations were successfully tested with real data taken from published experiments that describe redox signaling mediated by the oxidation of two protein tyrosine phosphatases, PTP1B and SHP-2, which are two of the few H2O2-sensing proteins with known kinetic parameters. Whereas for PTP1B estimated kinetic parameters fitted in general the present knowledge, for SHP-2 results obtained suggest that reactivity toward H2O2 as well as the rate of SHP-2 regeneration back to its reduced form are higher than previously thought. In conclusion, valuable quantitative kinetic data can be estimated from typical redox signaling experiments, thus improving our understanding about the complex processes that underlie the interplay between oxidative stress and redox signaling responses.

ATP modulates acute inflammation in vivo through dual oxidase 1-derived H2O2 production and NF-κB activation

Dual oxidase 1 (Duox1) is the NADPH oxidase responsible for the H2O2 gradient formed in tissues after injury to trigger the early recruitment of leukocytes. Little is known about the signals that modulate H2O2 release from DUOX1 and whether the H2O2 gradient can orchestrate the inflammatory response in vivo. In this study, we report on a dominant-negative form of zebrafish Duox1 that is able to inhibit endogenous Duox1 activity, H2O2 release and leukocyte recruitment after tissue injury, with none of the side effects associated with morpholino-mediated Duox1 knockdown. Using this specific tool, we found that ATP release following tissue injury activates purinergic P2Y receptors, and modulates Duox1 activity through phospholipase C (PLC) and intracellular calcium signaling in vivo. Furthermore, Duox1-derived H2O2 is able to trigger the NF-κB inflammatory signaling pathway. These data reveal that extracellular ATP acting as an early danger signal is responsible for the activation of Duox1 via a P2YR/PLC/Ca(2+) signaling pathway and the production of H2O2, which, in turn, is able to modulate in vivo not only the early recruitment of leukocytes to the wound but also the inflammatory response through activation of the NF-κB signaling pathway.