A quantitative study of NF-kappaB activation by H2O2: relevance in inflammation and synergy with TNF-alpha

The role of reactive oxygen species in the regulation of the blood-brain barrier

The blood-brain barrier (BBB) regulates the exchange of metabolites and cells between the blood and brain, and maintains central nervous system homeostasis. Various factors affect BBB barrier functions, including reactive oxygen species (ROS). ROS can act as stressors, damaging biological molecules, but they also serve as secondary messengers in intracellular signaling cascades during redox signaling. The impact of ROS on the BBB has been observed in multiple sclerosis, stroke, trauma, and other neurological disorders, making blocking ROS generation a promising therapeutic strategy for BBB dysfunction. However, it is important to consider ROS generation during normal BBB functioning for signaling purposes. This review summarizes data on proteins expressed by BBB cells that can be targets of redox signaling or oxidative stress. It also provides examples of signaling molecules whose impact may cause ROS generation in the BBB, as well as discusses the most common diseases associated with BBB dysfunction and excessive ROS generation, open questions that arise in the study of this problem, and possible ways to overcome them.

Role of Oxygen and Its Radicals in Peripheral Nerve Regeneration: From Hypoxia to Physoxia to Hyperoxia

Oxygen is compulsory for mitochondrial function and energy supply, but it has numerous more nuanced roles. The different roles of oxygen in peripheral nerve regeneration range from energy supply, inflammation, phagocytosis, and oxidative cell destruction in the context of reperfusion injury to crucial redox signaling cascades that are necessary for effective axonal outgrowth. A fine balance between reactive oxygen species production and antioxidant activity draws the line between physiological and pathological nerve regeneration. There is compelling evidence that redox signaling mediated by the Nox family of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases plays an important role in peripheral nerve regeneration. Further research is needed to better characterize the role of Nox in physiological and pathological circumstances, but the available data suggest that the modulation of Nox activity fosters great therapeutic potential. One of the promising approaches to enhance nerve regeneration by modulating the redox environment is hyperbaric oxygen therapy. In this review, we highlight the influence of various oxygenation states, i.e., hypoxia, physoxia, and hyperoxia, on peripheral nerve repair and regeneration. We summarize the currently available data and knowledge on the effectiveness of using hyperbaric oxygen therapy to treat nerve injuries and discuss future directions.

Immunometabolism in the pathogenesis of vitiligo

Vitiligo is a common depigmenting skin disorder characterized by the selective loss of melanocytes. Autoimmunity, genetic, environmental, and biochemical etiology have been proposed in vitiligo pathogenesis. However, the exact molecular mechanisms of vitiligo development and progression are unclear, particularly for immunometabolism. Sporadic studies have suggested mitochondrial dysfunction, enhanced oxidative stress, and specific defects in other metabolic pathways can promote dysregulation of innate and adaptive immune responses in vitiligo. These abnormalities appear to be driven by genetic and epigenetic factors modulated by stochastic events. In addition, glucose and lipid abnormalities in metabolism have been associated with vitiligo. Specific skin cell populations are also involved in the critical role of dysregulation of metabolic pathways, including melanocytes, keratinocytes, and tissue-resident memory T cells in vitiligo pathogenesis. Novel therapeutic treatments are also raised based on the abnormalities of immunometabolism. This review summarizes the current knowledge on immunometabolism reprogramming in the pathogenesis of vitiligo and novel treatment options.

Chemistry of Hydrogen Peroxide Formation and Elimination in Mammalian Cells, and Its Role in Various Pathologies

Hydrogen peroxide (H2O2) is a compound involved in some mammalian reactions and processes. It modulates and signals the redox metabolism of cells by acting as a messenger together with hydrogen sulfide (H2S) and the nitric oxide radical (•NO), activating specific oxidations that determine the metabolic response. The reaction triggered determines cell survival or apoptosis, depending on which downstream metabolic pathways are activated. There are several ways to produce H2O2 in cells, and cellular systems tightly control its concentration. At the cellular level, the accumulation of hydrogen peroxide can trigger inflammation and even apoptosis, and when its concentration in the blood reaches toxic levels, it can lead to bioenergetic failure. This review summarizes existing research from a chemical perspective on the role of H2O2 in various enzymatic pathways and how this biochemistry leads to physiological or pathological responses.

Effects of Functional Phenolics Dietary Supplementation on Athletes' Performance and Recovery: A Review

In recent years, many efforts have been made to identify micronutrients or nutritional strategies capable of preventing, or at least, attenuating, exercise-induced muscle damage and oxidative stress, and improving athlete performance. The reason is that most exercises induce various changes in mitochondria and cellular cytosol that lead to the generation of reactive species and free radicals whose accumulation can be harmful to human health. Among them, supplementation with phenolic compounds seems to be a promising approach since their chemical structure, composed of catechol, pyrogallol, and methoxy groups, gives them remarkable health-promoting properties, such as the ability to suppress inflammatory processes, counteract oxidative damage, boost the immune system, and thus, reduce muscle soreness and accelerate recovery. Phenolic compounds have also already been shown to be effective in improving temporal performance and reducing psychological stress and fatigue. Therefore, the aim of this review is to summarize and discuss the current knowledge on the effects of dietary phenolics on physical performance and recovery in athletes and sports practitioners. Overall, the reports show that phenolics exert important benefits on exercise-induced muscle damage as well as play a biological/physiological role in improving physical performance.

Eriodictyol Suppresses Porphyromonas gingivalis-Induced Reactive Oxygen Species Production by Gingival Keratinocytes and the Inflammatory Response of Macrophages

Porphyromonas gingivalis is a key pathogen of periodontitis, an inflammatory disease that affects the tooth-supporting tissues. The aim of the present study was to investigate the effects of the flavanone eriodictyol on P. gingivalis-induced reactive oxygen species (ROS) production by gingival keratinocytes and the inflammatory response of macrophages. Porphyromonas gingivalis and H2O2 acted synergistically to induce ROS production by keratinocytes. The presence of eriodictyol significantly attenuated ROS production in a dose-dependent manner. We used a macrophage model to show that eriodictyol decreases the secretion of IL-1β, IL-6, IL-8, and TNF-α induced by P. gingivalis. Evidence has been brought that this anti-inflammatory property of eriodictyol may be related to its ability to prevent the activation of the NF-κB signaling pathway by P. gingivalis. This periodontal pathogen was also found to be a potent inducer of matrix metalloproteinase (MMP) production by macrophages, including MMP-2, MMP-8, and MMP-9. Eriodictyol dose-dependently inhibited the production of all three MMPs. Lastly, eriodictyol inhibited the catalytic activity of both MMP-9 and P. gingivalis collagenase. In conclusion, eriodictyol may be a potential therapeutic agent for preventing and/or treating periodontal disease due to its antioxidant, anti-inflammatory, and anti-proteinase properties.

HBXIP induces anoikis resistance by forming a reciprocal feedback loop with Nrf2 to maintain redox homeostasis and stabilize Prdx1 in breast cancer

Anoikis resistance is an essential prerequisite for tumor metastasis, but the underlying molecular mechanisms remain unknown. Herein, we report that the oncoprotein hepatitis B X-interacting protein (HBXIP) is prominently upregulated in breast cancer cells following ECM detachment. Altering HBXIP expression can impair the anchorage-independent growth ability of tumor cells. Mechanistically, HBXIP, which binds to Kelch-like ECH-associated protein 1 (Keap1) to activate nuclear factor E2-related factor 2 (Nrf2), contains a cis-acting antioxidant response element (ARE) in the gene promoter and is a target gene of Nrf2. The HBXIP/Nrf2 axis forms a reciprocal positive feedback loop that reinforces the expression and tumor-promoting actions of each protein. In response to ECM detachment, Nrf2 reduces reactive oxygen species (ROS) accumulation, protects the mitochondrial membrane potential and increases cellular ATP, GSH and NADPH levels to maintain breast cancer cell survival. Meanwhile, the reinforcement of HBXIP induced by Nrf2 inhibits JNK1 activation by inhibiting ubiquitin-mediated degradation of Prdx1, which also plays an essential role in promoting ECM-detached cell survival. Furthermore, a strong positive correlation was identified between HBXIP expression and Prdx1 expression in clinical breast cancer tissues and TCGA Pan-Cancer Atlas clinical data of breast invasive carcinoma based on the cBioPortal cancer genomics database. Co-expression of HBXIP and Prdx1 predicts a poor prognosis for breast cancer patients. Collectively, our findings reveal a significant mechanism by which the HBXIP/Nrf2 feedback loop contributes to anoikis resistance by maintaining redox homeostasis and inhibiting JNK1 activation and support the likely therapeutic value of the HBXIP/Nrf2 axis in breast cancer patients.

Oxidative stress concept updated: Definitions, classifications, and regulatory pathways implicated

Reactive oxygen species were discovered in living organisms in the early 1950's and their action has been implicated in diverse biological processes. First formulated by H. Sies in 1985[57], the oxidative stress concept stimulated substantial interest in reactive oxygen species and it is now common that fundamental research in various biomedical fields includes mention of research on the involvement of oxidative stress. Such strong interest has resulted in the development of definitions and classifications of oxidative stress and much research progress in the field. Although we clearly understand the limitations of various definitions or classifications, such parameters may help to provide quantitative descriptions, compare related processes among different laboratories, and introduce some measurable parameters. This paper highlights recent advances in the areas of oxidative stress definitions and the classification of oxidative stresses. Such items are directly associated with our understanding of the molecular mechanisms involved in organismal responses to oxidative insults. The knowledge accumulated to date indicates that selective expression of specific genes is a central player in the adaptive response to oxidative stress and reversible oxidation of cysteine residues of sensor proteins is a key process regulating responses to oxidative stress.

Effects of oxidative stress-induced increases in Zn2+ concentrations in human gingival epithelial cells

BACKGROUND AND OBJECTIVE

Previous studies have reported that oxidative stress increases intracellular Zn²⁺ concentrations and induces cytotoxicity. However, no studies have investigated whether oxidative stress induces such changes in periodontal tissue cells. In the present study, we investigated the effect of oxidative stress on intracellular Zn²⁺ concentration in periodontium constituent cells and its potential relationship with periodontal disease.

METHODS

We analyzed changes in intracellular Zn²⁺ concentrations in human gingival epithelial (epi4) cells treated with hydrogen peroxide (H₂ O₂ ). The fluorescent probes FluoZin-3 AM and CellTracker Green CMFDA were used to detect intracellular Zn²⁺ and thiol groups, respectively. Western blot analyses, luciferase reporter assays, and real-time polymerase chain reaction (PCR) analyses were performed to examine the effect of intracellular Zn²⁺ on epi4 cells.

RESULTS

H₂ O₂ treatment increased intracellular concentrations of Zn²⁺ in epi4 cells by facilitating the movement of Zn²⁺ from cellular nonprotein thiols to the cytoplasm and promoting cell membrane permeability to Zn²⁺ . Furthermore, H₂ O₂ -induced increases in intracellular Zn²⁺ activated the p38 cAMP response element-binding protein/mitogen-activated protein kinase (p38 CREB/MAPK) cascade, upregulated nuclear factor kappa B (NF-κB) DNA binding, and increased the expression of inflammatory cytokines and matrix metallopeptidase-9 (MMP-9).

CONCLUSION

Increases in intracellular Zn²⁺ induced by oxidative stress activate signaling pathways involved in inflammation, potentially contributing to the progression of periodontal disease.

Nuclear Factor Kappa B Signaling Complexes in Acute Inflammation

Significance: Nuclear factor kappa B (NF-κB) is a master regulator of the inflammatory response and represents a key regulatory node in the complex inflammatory signaling network. In addition, selective NF-κB transcriptional activity on specific target genes occurs through the control of redox-sensitive NF-κB interactions. Recent Advances: The selective NF-κB response is mediated by redox-modulated NF-κB complexes with ribosomal protein S3 (RPS3), Pirin (PIR). cAMP response element-binding (CREB)-binding protein (CBP)/p300, peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), activator protein-1 (AP-1), signal transducer and activator of transcription 3 (STAT3), early growth response protein 1 (EGR-1), and SP-1. NF-κB is cooperatively coactivated with AP-1, STAT3, EGR-1, and SP-1 during the inflammatory process, whereas NF-κB complexes with CBP/p300 and PGC-1α regulate the expression of antioxidant genes. PGC-1α may act as selective repressor of phospho-p65 toward interleukin-6 (IL-6) in acute inflammation. p65 and nuclear factor erythroid 2-related factor 2 (NRF2) compete for binding to coactivator CBP/p300 playing opposite roles in the regulation of inflammatory genes. S-nitrosylation or tyrosine nitration favors the recruitment of specific NF-κB subunits to κB sites. Critical Issues: NF-κB is a redox-sensitive transcription factor that forms specific signaling complexes to regulate selectively the expression of target genes in acute inflammation. Protein-protein interactions with coregulatory proteins, other transcription factors, and chromatin-remodeling proteins provide transcriptional specificity to NF-κB. Furthermore, different NF-κB subunits may form distinct redox-sensitive homo- and heterodimers with distinct affinities for κB sites. Future Directions: Further research is required to elucidate the whole NF-κB interactome to fully characterize the complex NF-κB signaling network in redox signaling, inflammation, and cancer.

ROS induced by spring viraemia of carp virus activate the inflammatory response via the MAPK/AP-1 and PI3K signaling pathways

Spring viraemia of carp virus (SVCV) can cause a high mortality in common carp (Cyprinus carpio), and its main pathological processes include the inflammatory response. However, the detailed mechanism is still unclear. Reactive oxygen species (ROS) have been shown to play critical roles in the immune response, including inflammation, in different models. Our previous studies have demonstrated that SVCV infection results in the accumulation of ROS, including H₂O₂, in epithelioma papulosum cyprini (EPC) cells. In this study, we aimed to explore the relationship between H₂O₂ accumulation and inflammation during SVCV infection. After EPC cells were infected with SVCV, the expression levels of the inflammatory factors tumor necrosis factor (TNF)-α, cyclooxygenase (COX)-2, and interleukin (IL)-8 were up-regulated, while the expression of the anti-inflammatory factor interleukin (IL)-10 was down-regulated, compared with that in mock-infected EPC cells. The antioxidant N-acetyl-l-cysteine (NAC) could dampen the increased TNF-ɑ and COX-2 expression induced by SVCV and H₂O₂, suggesting a relationship between ROS accumulation and inflammation during SVCV infection. Dual luciferase reporter assays demonstrated that SVCV could not activate the NF-κB pathway. In addition, inhibition of NF-κB by pyrrolidine dithiocarbamate (PDTC) treatment had no effect on the expression of inflammatory factors. Furthermore, inhibition of the ERK, JNK, and p38MAPK signaling pathways by U0126, SP600125, and SB203580, respectively, reduced the expression of TNF-ɑ, COX-2, and IL-8, indicating that these three signaling pathways were all involved in the inflammatory response after SVCV infection. In addition, the PI3K signaling pathway was involved in the expression of the chemokine IL-8 in the SVCV-induced inflammatory response. We also showed that inhibition of the MAPK or PI3K signaling pathway facilitated the expression of SVCV-G as well as increased the SVCV viral titer. Altogether these results reveal the mechanism of the SVCV-mediated inflammatory response. Thus, targeting these signaling pathways may provide novel treatment strategies for SVCV-mediated diseases.

Neuronal Calcium Sensor 1 is up-regulated in response to stress to promote cell survival and motility in cancer cells

Changes in intracellular calcium (Ca²⁺) signaling can modulate cellular machinery required for cancer progression. Neuronal calcium sensor 1 (NCS1) is a ubiquitously expressed Ca²⁺‐binding protein that promotes tumor aggressiveness by enhancing cell survival and metastasis. However, the underlying mechanism by which NCS1 contributes to increased tumor aggressiveness has yet to be identified. In this study, we aimed to determine (a) whether NCS1 expression changes in response to external stimuli, (b) the importance of NCS1 for cell survival and migration, and (c) the cellular mechanism(s) through which NSC1 modulates these outcomes. We found that NCS1 abundance increases under conditions of stress, most prominently after stimulation with the pro‐inflammatory cytokine tumor necrosis factor α, in a manner dependent on nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NFκB). We found that NFκB signaling is activated in human breast cancer tissue, which was accompanied by an increase in NCS1 mRNA expression. Further exploration into the relevance of NCS1 in breast cancer progression showed that knockout of NCS1 (NCS1 KO) caused decreased cell survival and motility, increased baseline intracellular Ca²⁺ levels, and decreased inositol 1,4,5‐trisphosphate‐mediated Ca²⁺ responses. Protein kinase B (Akt) activity was decreased in NCS1 KO cells, which could be rescued by buffering intracellular Ca²⁺. Conversely, Akt activity was increased in cells overexpressing NCS1 (NCS1 OE). We therefore conclude that NCS1 acts as cellular stress response protein up‐regulated by stress‐induced NFκB signaling and that NCS1 influences cell survival and motility through effects on Ca²⁺ signaling and Akt pathway activation.

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.

Cho S, Britton W, S. Kern T, Antonetti DA, Hellström A, E.H. Smith L. Targeting Neurovascular Interaction in Retinal Disorders

The tightly structured neural retina has a unique vascular network comprised of three interconnected plexuses in the inner retina (and choroid for outer retina), which provide oxygen and nutrients to neurons to maintain normal function. Clinical and experimental evidence suggests that neuronal metabolic needs control both normal retinal vascular development and pathological aberrant vascular growth. Particularly, photoreceptors, with the highest density of mitochondria in the body, regulate retinal vascular development by modulating angiogenic and inflammatory factors. Photoreceptor metabolic dysfunction, oxidative stress, and inflammation may cause adaptive but ultimately pathological retinal vascular responses, leading to blindness. Here we focus on the factors involved in neurovascular interactions, which are potential therapeutic targets to decrease energy demand and/or to increase energy production for neovascular retinal disorders.

Implantation Time Has No Effect on the Morphology and Extent of Previously Reported "Degradation" of Prolene Pelvic Mesh

OBJECTIVES

Prolene polypropylene ("Prolene") meshes demonstrate no in vivo degradation, yet some claim degradation continues until no more Prolene polypropylene can be oxidized. We studied whether implantation time affects the morphology/extent of previously reported as cracking/degradation of completely cleaned Prolene explants.

METHODS

Urogynecological explants (248 patients) were collected. After excluding non-Prolene/unknown meshes and those without known implantation times, completely cleaned explants (n = 205; 0.2-14.4 years implantation) were analyzed with light microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. Based on implant times and storage (fixative or dry), representative specimens were randomly selected for comparison. Controls were unused ("exemplar") TVT specimens with and without intentional oxidation via ultraviolet light exposure.

RESULTS

Prolene explants included 31 dry (18 TVT; 7 Prolift; 4 Gynemesh; 2 others) and 174 wet (87 TVT; 47 Prolift; 10 Gynemesh; 30 others) specimens. Specimens had similar morphologies before cleaning. Progressive cleaning removed tissue and cracked tissue-related material exposing smooth, unoxidized, and nondegraded fibers, with no visible gradient-type/ductile damage. Fourier transform infrared spectroscopy of the explants confirmed progressive loss of proteins. Cleaning intentionally oxidized exemplars did not remove oxidized carbonyl frequencies and showed deep cracks and gross fiber rupture/embrittlement, unlike the explants and nonoxidized exemplars.

CONCLUSIONS

If in vivo Prolene degradation exists, there should be wide-ranging crack morphology and nonuniform crack penetration, as well as more cracking, degradation, and physical breakage for implants of longer implantation times, but this was not the case. There is no morphologic or spectral/chemical evidence of Prolene mesh degradation after up to 14.4 years in vivo.

Reversible redox-responsive 1H/19F MRI molecular probes

The redox-responsive manganese(ii)/(iii) complexes serve as a pair of reversible probes for ¹H MRI and ¹⁹F MRI of biological redox species.

The potential of lipid-polymer nanoparticles as epigenetic and ROS control approaches for COPD

Chronic obstructive pulmonary disease (COPD) is a lung disease caused by an inflammatory response to various inhaled toxins, especially cigarette smoke. Reactive oxygen species (ROS) and epigenetic abnormality are intimately related to the pathology of COPD, and the overproduction of ROS results in a decrease of histone deacetylase 2 (HDAC2), leading to glucocorticoid resistance. Therefore, a novel treatment that simultaneously reduces ROS level and glucocorticoid resistance is urgently needed. In this study, we developed a codelivery system using core-shell type lipid-polymer nanoparticles (LPNs) composed of a poly(lactic acid) (PLA) core encapsulating a potent antioxidant Mn-porphyrin dimer (MnPD) and a cationic lipid (DOTAP) shell that binds HDAC2-encoding plasmid DNA (pHDAC2), as a new therapeutic approach toward COPD. The transfection of pHDAC2 combined with the elimination of ROS by MnPD exhibited a significant enhancement of intracellular HDAC2 expression levels, suggesting that the multi-antioxidative activity of MnPD plays a crucial role in the expression of HDAC2. Moreover, treatment with LPNs efficiently ameliorated the steroid resistance in COPD models in vitro as evidenced by the lowered expression levels of IL-8. Recovery from mitochondrial dysfunction may be the mechanism underlying the action of LPNs. The PLA-MnPD/DOTAP/pHDAC2 system proposed offers a new therapeutic approach for COPD based on the synergism of ROS elimination and HDAC2 expression.

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.

Oxidative stress pathways in pancreatic β-cells and insulin-sensitive cells and tissues: importance to cell metabolism, function, and dysfunction

It is now accepted that nutrient abundance in the blood, especially glucose, leads to the generation of reactive oxygen species (ROS), ultimately leading to increased oxidative stress in a variety of tissues. In the absence of an appropriate compensatory response from antioxidant mechanisms, the cell, or indeed the tissue, becomes overwhelmed by oxidative stress, leading to the activation of intracellular stress-associated pathways. Activation of the same or similar pathways also appears to play a role in mediating insulin resistance, impaired insulin secretion, and late diabetic complications. The ability of antioxidants to protect against the oxidative stress induced by hyperglycemia and elevated free fatty acid (FFA) levels in vitro suggests a causative role of oxidative stress in mediating the latter clinical conditions. In this review, we describe common biochemical processes associated with oxidative stress driven by hyperglycemia and/or elevated FFA and the resulting clinical outcomes: β-cell dysfunction and peripheral tissue insulin resistance.

Retinal Vasculature in Development and Diseases

The retina is one of the most metabolically active tissues in the body, consuming high levels of oxygen and nutrients. A well-organized ocular vascular system adapts to meet the metabolic requirements of the retina to ensure visual function. Pathological conditions affect growth of the blood vessels in the eye. Understanding the neuronal biological processes that govern retinal vascular development is of interest for translational researchers and clinicians to develop preventive and interventional therapeutics for vascular eye diseases that address early drivers of abnormal vascular growth. This review summarizes the current knowledge of the cellular and molecular processes governing both physiological and pathological retinal vascular development, which is dependent on the interaction among retinal cell populations, including neurons, glia, immune cells, and vascular endothelial cells. We also review animal models currently used for studying retinal vascular development.

Berberine protects immortalized line of human melanocytes from H2O2-induced oxidative stress via activation of Nrf2 and Mitf signaling pathway

BACKGROUND

Oxidative stress plays important roles in the pathogenesis of vitiligo. The removal of hydrogen peroxided (H₂O₂) has been established to be beneficial to vitiligo patients. Berberine (BBR), a natural isoquinoline alkaloid, has antioxidant activity, however, whether BBR can defend human melanocytes against oxidative injury remains to be elucidated.

OBJECTIVE

In the present study, we investigated the potential protective effect of BBR against oxidative stress on an immortalized normal human melanocyte cell line PIG1.

METHODS

Generally, PIG1 cells were pretreated with various concentrations of BBR for 1 h followed by exposure to 1.0 mM H₂O₂ for 24 h. Cell apoptosis, intracellular reactive oxygen species (ROS) levels were assessed through flow cytometry. Cell apoptosis, melanogenesis and the activation of Nrf2-ARE and Mitf signaling pathway were assayed.

RESULTS

Our results showed that cell viability rose and intracellular ROS generation, cell apoptosis of melanocytes decreased significantly in response to H₂O₂ through pretreatment with BBR. Furthermore, We found that BBR can dramatically induce Nrf2 nuclear translocation, increase total Nrf2 levels and enhance ARE activity. Besides, Nrf2-siRNA transfection can abrogate the protection of BBR in melanocytes against oxidative injury. At last, we verified that BBR could facilitate melanogenesis function via modulation of Mitf and its target proteins.

CONCLUSION

The results above suggest that BBR can protect melanocytes against oxidative stress via its anti-oxidative activity. Also, we found H₂O₂-induced activation of NFκB was inhibited by BBR. Therefore, it is worthy of investigation BBR as a potential drug for treatment of vitiligo.

Clair WH, St. Clair DK. Redox Paradox: A Novel Approach to Therapeutics-Resistant Cancer

SIGNIFICANCE

Cancer cells that are resistant to radiation and chemotherapy are a major problem limiting the success of cancer therapy. Aggressive cancer cells depend on elevated intracellular levels of reactive oxygen species (ROS) to proliferate, self-renew, and metastasize. As a result, these aggressive cancers maintain high basal levels of ROS compared with normal cells. The prominence of the redox state in cancer cells led us to consider whether increasing the redox state to the condition of oxidative stress could be used as a successful adjuvant therapy for aggressive cancers. Recent Advances: Past attempts using antioxidant compounds to inhibit ROS levels in cancers as redox-based therapy have met with very limited success. However, recent clinical trials using pro-oxidant compounds reveal noteworthy results, which could have a significant impact on the development of strategies for redox-based therapies.

CRITICAL ISSUES

The major objective of this review is to discuss the role of the redox state in aggressive cancers and how to utilize the shift in redox state to improve cancer therapy. We also discuss the paradox of redox state parameters; that is, hydrogen peroxide (H2O2) as the driver molecule for cancer progression as well as a target for cancer treatment.

FUTURE DIRECTIONS

Based on the biological significance of the redox state, we postulate that this system could potentially be used to create a new avenue for targeted therapy, including the potential to incorporate personalized redox therapy for cancer treatment.

The manganese(III) porphyrin MnTnHex-2-PyP5+ modulates intracellular ROS and breast cancer cell migration: Impact on doxorubicin-treated cells

Manganese(III) porphyrins (MnPs) are superoxide dismutase (SOD) mimics with demonstrated beneficial effects in cancer treatment in combination with chemo- and radiotherapy regimens. Despite the ongoing clinical trials, little is known about the effect of MnPs on metastasis, being therefore essential to understand how MnPs affect this process. In the present work, the impact of the MnP MnTnHex-2-PyP⁵⁺ in metastasis-related processes was assessed in breast cancer cells (MCF-7 and MDA-MB-231), alone or in combination with doxorubicin (dox). The co-treatment of cells with non-cytotoxic concentrations of MnP and dox altered intracellular ROS, increasing H₂O₂. While MnP alone did not modify cell migration, the co-exposure led to a reduction in collective cell migration and chemotaxis. In addition, the MnP reduced the dox-induced increase in random migration of MDA-MB-231 cells. Treatment with either MnP or dox decreased the proteolytic invasion of MDA-MB-231 cells, although the effect was more pronounced upon co-exposure with both compounds. Moreover, to explore the cellular mechanisms underlying the observed effects, cell adhesion, spreading, focal adhesions, and NF-κB activation were also studied. Although differential effects were observed according to the endpoints analysed, overall, the alterations induced by MnP in dox-treated cells were consistent with a therapeutically favorable outcome.

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MnPs are SOD mimics with potential therapeutic applications in cancer.

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The impact of an MnP on breast cancer metastasis-related processes was assessed.

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Treatment with MnP+dox decreased collective cell migration, chemotaxis and invasion.

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MnP also reduced the dox-induced increase in random migration of MDA-MB-231 cells.

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Combination of MnP with dox revealed therapeutically favorable effects.

Reactive Oxygen Species and NOX Enzymes Are Emerging as Key Players in Cutaneous Wound Repair

Our understanding of the role of oxygen in cell physiology has evolved from its long-recognized importance as an essential factor in oxidative metabolism to its recognition as an important player in cell signaling. With regard to the latter, oxygen is needed for the generation of reactive oxygen species (ROS), which regulate a number of different cellular functions including differentiation, proliferation, apoptosis, migration, and contraction. Data specifically concerning the role of ROS-dependent signaling in cutaneous wound repair are very limited, especially regarding wound contraction. In this review we provide an overview of the current literature on the role of molecular and reactive oxygen in the physiology of wound repair as well as in the pathophysiology and therapy of chronic wounds, especially under ischemic and hyperglycemic conditions.

Therapeutic activity of superoxide dismutase-containing enzymosomes on rat liver ischaemia-reperfusion injury followed by magnetic resonance microscopy

Liver ischaemia-reperfusion injury (IRI) may occur during hepatic surgery and is unavoidable in liver transplantation. Superoxide dismutase enzymosomes (SOD-enzymosomes), liposomes where SOD is at the liposomal surface expressing enzymatic activity in intact form without the need of liposomal disruption, were developed with the aim of having a better insight into its antioxidant therapeutic outcome in IRI. We also aimed at validating magnetic resonance microscopy (MRM) at 7T as a tool to follow IRI. SOD-enzymosomes were characterized and tested in a rat ischaemia-reperfusion model and the therapeutic outcome was compared with conventional long circulating SOD liposomes and free SOD using biochemical liver injury biomarkers, histology and MRM. MRM results correlated with those obtained using classical biochemical biomarkers of liver injury and liver histology. Moreover, MRM images suggested that the therapeutic efficacy of both SOD liposomal formulations used was related to prevention of peripheral biliary ductular damage and disrupted vascular architecture. Therefore, MRM at 7T is a useful technique to follow IRI. SOD-enzymosomes were more effective than conventional liposomes in reducing liver ischaemia-reperfusion injury and this may be due to a short therapeutic window.

Quantitative biology of hydrogen peroxide signaling

Hydrogen peroxide (H₂O₂) controls signaling pathways in cells by oxidative modulation of the activity of redox sensitive proteins denominated redox switches. Here, quantitative biology concepts are applied to review how H₂O₂ fulfills a key role in information transmission. Equations described lay the foundation of H₂O₂ signaling, give new insights on H₂O₂ signaling mechanisms, and help to learn new information from common redox signaling experiments. A key characteristic of H₂O₂ signaling is that the ratio between reduction and oxidation of redox switches determines the range of H₂O₂ concentrations to which they respond. Thus, a redox switch with low H₂O₂-dependent oxidability and slow reduction rate responds to the same range of H₂O₂ concentrations as a redox switch with high H₂O₂-dependent oxidability, but that is rapidly reduced. Yet, in the first case the response time is slow while in the second case is rapid. H₂O₂ sensing and transmission of information can be done directly or by complex mechanisms in which oxidation is relayed between proteins before oxidizing the final regulatory redox target. In spite of being a very simple molecule, H₂O₂ has a key role in cellular signaling, with the reliability of the information transmitted depending on the inherent chemical reactivity of redox switches, on the presence of localized H₂O₂ pools, and on the molecular recognition between redox switches and their partners.

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Hydrogen peroxide signaling proceeds through oxidation of redox switches.

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Oxidation of redox switches can be direct or mediated by highly reactive sensors.

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Response of redox switches is controlled by their oxidability and reduction rate.

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Localized protein interactions ensure the accuracy of information transmission.

Modulating and Measuring Intracellular H2O2 Using Genetically Encoded Tools to Study Its Toxicity to Human Cells

Reactive oxygen species (ROS) such as H₂O₂ play paradoxical roles in mammalian physiology. It is hypothesized that low, baseline levels of H₂O₂ are necessary for growth and differentiation, while increased intracellular H₂O₂ concentrations are associated with pathological phenotypes and genetic instability, eventually reaching a toxic threshold that causes cell death. However, the quantities of intracellular H₂O₂ that lead to these different responses remain an unanswered question in the field. To address this question, we used genetically encoded constructs that both generate and quantify H₂O₂ in a dose-response study of H₂O₂-mediated toxicity. We found that, rather than a simple concentration-response relationship, a combination of intracellular concentration and the cumulative metric of H₂O₂ concentration multiplied by time (i.e., the area under the curve) determined the occurrence and level of cell death. Establishing the quantitative relationship between H₂O₂ and cell toxicity promotes a deeper understanding of the intracellular effects of H₂O₂ specifically as an individual reactive oxygen species, and it contributes to an understanding of its role in various redox-related diseases.

Insight into the messenger role of reactive oxygen intermediates in immunostimulated hemocytes from the scallop Argopecten purpuratus

Reactive oxygen intermediates (ROI) are metabolites produced by aerobic cells which have been linked to oxidative stress. Evidence reported in vertebrates indicates that ROI can also act as messengers in a variety of cellular signaling pathways, including those involved in innate immunity. In a recent study, an inhibitor of NF-kB transcription factors was identified in the scallop Argopecten purpuratus, and its functional characterization suggested that it may regulate the expression of the big defensin antimicrobial peptide ApBD1. In order to give new insights into the messenger role of ROI in the immune response of bivalve mollusks, the effect of ROI production on gene transcription of ApBD1 was assessed in A. purpuratus. The results showed that 48 h-cultured hemocytes were able to display phagocytic activity and ROI production in response to the β-glucan zymosan. The immune stimulation also induced the transcription of ApBD1, which was upregulated in cultured hemocytes. After neutralizing the ROI produced by the stimulated hemocytes with the antioxidant trolox, the transcription of ApBD1 was reduced near to base levels. The results suggest a potential messenger role of intracellular ROI on the regulation of ApBD1 transcription during the immune response of scallops.

LncRNAs H19 and HULC, activated by oxidative stress, promote cell migration and invasion in cholangiocarcinoma through a ceRNA manner

Background

Long non-coding RNAs (lncRNAs) are known to play important roles in different cell contexts, including cancers. However, little is known about lncRNAs in cholangiocarcinoma (CCA), a cholangiocyte malignancy with poor prognosis, associated with chronic inflammation and damage to the biliary epithelium. The aim of the study is to identify if any lncRNA might associate with inflammation or oxidative stress in CCA and regulate the disease progression.

Methods

In this study, RNA-seqs datasets were used to identify aberrantly expressed lncRNAs. Small interfering RNA and overexpressed plasmids were used to modulate the expression of lncRNAs, and luciferase target assay RNA immunoprecipitation (RIP) was performed to explore the mechanism of miRNA-lncRNA sponging.

Results

We firstly analyzed five available RNA-seqs datasets to investigate aberrantly expressed lncRNAs which might associate with inflammation or oxidative stress. We identified that two lncRNAs, H19 and HULC, were differentially expressed among all the samples under the treatment of hypoxic or inflammatory factors, and they were shown to be stimulated by short-term oxidative stress responses to H₂O₂ and glucose oxidase in CCA cell lines. Further studies revealed that these two lncRNAs promoted cholangiocyte migration and invasion via the inflammation pathway. H19 and HULC functioned as competing endogenous RNAs (ceRNAs) by sponging let-7a/let-7b and miR-372/miR-373, respectively, which activate pivotal inflammation cytokine IL-6 and chemokine receptor CXCR4.

Conclusions

Our study revealed that H19 and HULC, up-regulated by oxidative stress, regulate CCA cell migration and invasion by targeting IL-6 and CXCR4 via ceRNA patterns of sponging let-7a/let-7b and miR-372/miR-373, respectively. The results suggest that these lncRNAs might be the chief culprits of CCA pathogenesis and progression. The study provides new insight into the mechanism linking lncRNA function with CCA and may serve as novel targets for the development of new countermeasures of CCA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0348-0) contains supplementary material, which is available to authorized users.

In Situ Impregnation of Silver Nanoclusters in Microporous Chitosan-PEG Membranes as an Antibacterial and Drug Delivery Percutaneous Device

An in situ synthesis method for preparing silver nanoclusters (AgNCs) embedded in chitosan-polyethylene glycol (CS-PEG) membranes is disclosed. The aim is to develop implantable multifunctional devices for biofilm inhibition and drug release to reduce percutaneous device related complications (PDRCs). A multiple array of characterization techniques confirmed the formation of fluorescent AgNCs with sizes of ∼3 nm uniformly distributed in CS-PEG matrix and their active role in determining the fraction and interconnectivity of the microporous membranes. The presence and increasing contents of AgNCs enhanced the mechanical stability of membranes and decreased their susceptibility to degradation in the presence of lysozyme and H₂O₂. Moreover, the presence and increasing concentrations of AgNCs hindered biofilm formation against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) and enabled a sustainable release of an anti-inflammatory drug naproxen in vitro until 24 h. The overall results gathered and reported in this work make the AgNCs impregnated CS-PEG membranes highly promising multifunctional devices combining efficient antibacterial activity and biocompatibility with active local drug delivery.

Hydrogen peroxide detection with high specificity in living cells and inflamed tissues

Hydrogen peroxide (H2O2) detection in biological systems is of significant importance, which act as critical second messenger in fundamental biological processes. Here, we report on a chemoselective fluorescent naphthylimide peroxide probe (NPP) for the H2O2 detection in vitro and in vivo. NPP is a phenylboronic acid-caged chromophore that selectively responds to H2O2 through a self-immolate mechanism. NPP exhibited high sensitivity and selectivity to H2O2 with distinctive fluorescence change due to the excellent two-photon excitation property, which permits the facile detection of inflammation produced H2O2 and offers chance to monitor the inflammatory stages in diseased cells.

Apocynin and ebselen reduce influenza A virus-induced lung inflammation in cigarette smoke-exposed mice

Influenza A virus (IAV) infections are a common cause of acute exacerbations of chronic obstructive pulmonary disease (AECOPD). Oxidative stress is increased in COPD, IAV-induced lung inflammation and AECOPD. Therefore, we investigated whether targeting oxidative stress with the Nox2 oxidase inhibitors and ROS scavengers, apocynin and ebselen could ameliorate lung inflammation in a mouse model of AECOPD. Male BALB/c mice were exposed to cigarette smoke (CS) generated from 9 cigarettes per day for 4 days. On day 5, mice were infected with 1 × 10(4.5) PFUs of the IAV Mem71 (H3N1). BALF inflammation, viral titers, superoxide production and whole lung cytokine, chemokine and protease mRNA expression were assessed 3 and 7 days post infection. IAV infection resulted in a greater increase in BALF inflammation in mice that had been exposed to CS compared to non-smoking mice. This increase in BALF inflammation in CS-exposed mice caused by IAV infection was associated with elevated gene expression of pro-inflammatory cytokines, chemokines and proteases, compared to CS alone mice. Apocynin and ebselen significantly reduced the exacerbated BALF inflammation and pro-inflammatory cytokine, chemokine and protease expression caused by IAV infection in CS mice. Targeting oxidative stress using apocynin and ebselen reduces IAV-induced lung inflammation in CS-exposed mice and may be therapeutically exploited to alleviate AECOPD.

Hydrogen peroxide regulates cell adhesion through the redox sensor RPSA

To become metastatic, a tumor cell must acquire new adhesion properties that allow migration into the surrounding connective tissue, transmigration across endothelial cells to reach the blood stream and, at the site of metastasis, adhesion to endothelial cells and transmigration to colonize a new tissue. Hydrogen peroxide (H2O2) is a redox signaling molecule produced in tumor cell microenvironment with high relevance for tumor development. However, the molecular mechanisms regulated by H2O2 in tumor cells are still poorly known. The identification of H2O2-target proteins in tumor cells and the understanding of their role in tumor cell adhesion are essential for the development of novel redox-based therapies for cancer. In this paper, we identified Ribosomal Protein SA (RPSA) as a target of H2O2 and showed that RPSA in the oxidized state accumulates in clusters that contain specific adhesion molecules. Furthermore, we showed that RPSA oxidation improves cell adhesion efficiency to laminin in vitro and promotes cell extravasation in vivo. Our results unravel a new mechanism for H2O2-dependent modulation of cell adhesion properties and identify RPSA as the H2O2 sensor in this process. This work indicates that high levels of RPSA expression might confer a selective advantage to tumor cells in an oxidative environment.

Controlled intracellular generation of reactive oxygen species in human mesenchymal stem cells using porphyrin conjugated nanoparticles

Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(II) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(II) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn(II) porphyrin and high numbers of irradiations of excitation light were found to generate greater amounts of ROS. A novel dye, which is transformed into fluorescent 7-hydroxy-4-trifluoromethyl-coumarin in the presence of hydrogen peroxide, provided an indirect indicator for cumulative ROS production. The mitochondrial membrane potential was monitored to investigate the destructive effect of increased intracellular ROS production. Flow cytometric analysis of nanoparticle treated hMSCs suggested irradiation with excitation light signalled controlled apoptotic cell death, rather than uncontrolled necrotic cell death. Increased intracellular ROS production did not induce phenotypic changes in hMSC subcultures.

Preclinical murine models of Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) is a major incurable global health burden and is the 4th leading cause of death worldwide. It is believed that an exaggerated inflammatory response to cigarette smoke causes progressive airflow limitation. This inflammation, where macrophages, neutrophils and T lymphocytes are prominent, leads to oxidative stress, emphysema, small airway fibrosis and mucus hypersecretion. Much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities and infectious (viral and bacterial) exacerbations (AECOPD). Comorbidities, defined as other chronic medical conditions, in particular skeletal muscle wasting and cardiovascular disease markedly impact on disease morbidity, progression and mortality. The mechanisms and mediators underlying COPD and its comorbidities are poorly understood and current COPD therapy is relatively ineffective. Thus, there is an obvious need for new therapies that can prevent the induction and progression of COPD and effectively treat AECOPD and comorbidities of COPD. Given that access to COPD patients can be difficult and that clinical samples often represent a "snapshot" at a particular time in the disease process, many researchers have used animal modelling systems to explore the mechanisms underlying COPD, AECOPD and comorbidities of COPD with the goal of identifying novel therapeutic targets. This review highlights the mouse models used to define the cellular, molecular and pathological consequences of cigarette smoke exposure and the recent advances in modelling infectious exacerbations and comorbidities of COPD.

TPN-associated intestinal epithelial cell atrophy is modulated by TLR4/EGF signaling pathways

Recent studies suggest a close interaction between epidermal growth factor (EGF) and TLR signaling in the modulation of intestinal epithelial cell (IEC) proliferation; however, how these signaling pathways adjust IEC proliferation is poorly understood. We utilized a model of total parenteral nutrition (TPN), or enteral nutrient deprivation, to study this interaction as TPN results in mucosal atrophy due to decreased IEC proliferation and increased apoptosis. We identified the novel finding of decreased mucosal atrophy in TLR4 knockout (TLR4KO) mice receiving TPN. We hypothesized that EGF signaling is preserved in TLR4KO-TPN mice and prevents mucosal atrophy. C57Bl/6 and strain-matched TLR4KO mice were provided either enteral feeding or TPN. IEC proliferation and apoptosis were measured. Cytokine and growth factor abundances were detected in both groups. To examine interdependence of these pathways, ErbB1 pharmacologic blockade was used. The marked decline in IEC proliferation with TPN was nearly prevented in TLR4KO mice, and intestinal length was partially preserved. EGF was significantly increased, and TNF-α decreased in TLR4KO-TPN versus wild-type (WT)-TPN mice. Apoptotic positive crypt cells were 15-fold higher in WT-TPN versus TLR4KO-TPN mice. Bcl-2 was significantly increased in TLR4KO-TPN mice, while Bax decreased 10-fold. ErbB1 blockade prevented this otherwise protective effect in TLR4KO-sTPN mice. TLR4 blockade significantly prevented TPN-associated atrophy by preserving proliferation and preventing apoptosis. This is driven by a reduction in TNF-α abundance and increased EGF. Potential manipulation of this regulatory pathway may have significant clinical potential to prevent TPN-associated atrophy.

Cardioprotective effects of melatonin against myocardial injuries induced by chronic intermittent hypoxia in rats

Obstructive sleep apnea (OSA) associated with chronic intermittent hypoxia (CIH) increases the morbidity and mortality of ischemic heart disease in patients. Yet, there is a paucity of preventive measures targeting the pathogenesis of CIH-induced myocardial injury. We examined the cardioprotective effect of melatonin against the inflammation, fibrosis and the deteriorated sarcoplasmic reticulum (SR) Ca(2+) homeostasis, and ischemia/reperfusion (I/R)-induced injury exacerbated by CIH. Adult male Sprague Dawley rats that had received a daily injection of melatonin (10 mg/kg) or vehicle were exposed to CIH treatment mimicking a severe OSA condition for 4 wk. Systolic pressure, heart weights, and malondialdehyde were significantly increased in hypoxic rats but not in the melatonin-treated group, when compared with the normoxic control. Levels of the expression of inflammatory cytokines (TNF-α, IL-6, and COX-2) and fibrotic markers (PC1 and TGF-β) were significantly elevated in the hypoxic group but were normalized by melatonin. Additionally, infarct size of isolated hearts with regional I/R was substantial in the hypoxic group treated with vehicle but not in the melatonin-treated group. Moreover, melatonin treatment mitigated the SR-Ca(2+) homeostasis in the cardiomyocyte during I/R with (i) Ca(2+) overloading, (ii) decreased SR-Ca(2+) content, (iii) lowered expression and activity of Ca(2+) -handling proteins (SERCA2a and NCX1),and (iv) decreased expressions of CAMKII and phosphorylated eNOS(ser1177). Furthermore, melatonin ameliorated the level of expression of antioxidant enzymes (CAT and MnSOD) and NADPH oxidase (p22 and NOX2). Results support a prophylactic usage of melatonin in OSA patients, which protects against CIH-induced myocardial inflammation and fibrosis with impaired SR-Ca(2+) handling and exacerbated I/R injury.

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.

Quantifying intracellular hydrogen peroxide perturbations in terms of concentration

Molecular level, mechanistic understanding of the roles of reactive oxygen species (ROS) in a variety of pathological conditions is hindered by the difficulties associated with determining the concentration of various ROS species. Here, we present an approach that converts fold-change in the signal from an intracellular sensor of hydrogen peroxide into changes in absolute concentration. The method uses extracellular additions of peroxide and an improved biochemical measurement of the gradient between extracellular and intracellular peroxide concentrations to calibrate the intracellular sensor. By measuring peroxiredoxin activity, we found that this gradient is 650-fold rather than the 7–10-fold that is widely cited. The resulting calibration is important for understanding the mass-action kinetics of complex networks of redox reactions, and it enables meaningful characterization and comparison of outputs from endogenous peroxide generating tools and therapeutics across studies.

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2-cys peroxiredoxin is the dominant scavenger of H₂O₂ in mammalian cells.

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H₂O₂ gradient across the plasma membrane is ~650-fold, 100 times higher than cited in literature.

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We developed an approach that converts fold-change in H₂O₂ sensor HyPer into change in actual concentration.

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The range of intracellular perturbations associated with the onset of apoptosis is less than 10 nM.

Effect of plant extracts on H2O2-induced inflammatory gene expression in macrophages

Background

Arctium lappa (AL), Camellia sinensis (CS), Echinacea angustifolia, Eleutherococcus senticosus, Panax ginseng (PG), and Vaccinium myrtillus (VM) are plants traditionally used in many herbal formulations for the treatment of various conditions. Although they are well known and already studied for their anti-inflammatory properties, their effects on H₂O₂-stimulated macrophages are a novel area of study.

Materials and methods

Cell viability was tested after treatment with increasing doses of H₂O₂ and/or plant extracts at different times of incubation to identify the optimal experimental conditions. The messenger (m)RNA expression of TNFα, COX2, IL1β, NFκB1, NFκB2, NOS2, NFE2L2, and PPARγ was analyzed in macrophages under H₂O₂ stimulation. The same genes were also quantified after plant extract treatment on cells pre-stimulated with H₂O₂.

Results

A noncytotoxic dose (200 μM) of H₂O₂ induced active mRNA expression of COX2, IL1β, NFE2L2, NFκB1, NFκB2, NOS2, and TNFα, while PPARγ was depressed. The expression of all genes tested was significantly (P<0.001) regulated by plant extracts after pre-stimulation with H₂O₂. COX2 was downregulated by AL, PG, and VM. All extracts depressed IL1β expression, but upregulated NFE2L2. NFκB1, NFκB2, and TNFα were downregulated by AL, CS, PG, and VM. NOS2 was inhibited by CS, PG, and VM. PPARγ was decreased only after treatment with E. angustifolia and E. senticosus.

Conclusion

The results of the present study indicate that the stimulation of H₂O₂ on RAW267.4 cells induced the transcription of proinflammatory mediators, showing that this could be an applicable system by which to activate macrophages. Plant extracts from AL, CS, PG, and VM possess in vitro anti-inflammatory activity on H₂O₂-stimulated macrophages by modulating key inflammation mediators. Further in vitro and in vivo investigation into molecular mechanisms modulated by herbal extracts should be undertaken to shed light on the development of novel modulating therapeutic strategies.

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.

Hydrogen peroxide sensing, signaling and regulation of transcription factors

The regulatory mechanisms by which hydrogen peroxide (H₂O₂) modulates the activity of transcription factors in bacteria (OxyR and PerR), lower eukaryotes (Yap1, Maf1, Hsf1 and Msn2/4) and mammalian cells (AP-1, NRF2, CREB, HSF1, HIF-1, TP53, NF-κB, NOTCH, SP1 and SCREB-1) are reviewed. The complexity of regulatory networks increases throughout the phylogenetic tree, reaching a high level of complexity in mammalians. Multiple H₂O₂ sensors and pathways are triggered converging in the regulation of transcription factors at several levels: (1) synthesis of the transcription factor by upregulating transcription or increasing both mRNA stability and translation; (ii) stability of the transcription factor by decreasing its association with the ubiquitin E3 ligase complex or by inhibiting this complex; (iii) cytoplasm–nuclear traffic by exposing/masking nuclear localization signals, or by releasing the transcription factor from partners or from membrane anchors; and (iv) DNA binding and nuclear transactivation by modulating transcription factor affinity towards DNA, co-activators or repressors, and by targeting specific regions of chromatin to activate individual genes. We also discuss how H₂O₂ biological specificity results from diverse thiol protein sensors, with different reactivity of their sulfhydryl groups towards H₂O₂, being activated by different concentrations and times of exposure to H₂O₂. The specific regulation of local H₂O₂ concentrations is also crucial and results from H₂O₂ localized production and removal controlled by signals. Finally, we formulate equations to extract from typical experiments quantitative data concerning H₂O₂ reactivity with sensor molecules. Rate constants of 140 M⁻¹ s⁻¹ and ≥1.3 × 10³ M⁻¹ s⁻¹ were estimated, respectively, for the reaction of H₂O₂ with KEAP1 and with an unknown target that mediates NRF2 protein synthesis. In conclusion, the multitude of H₂O₂ targets and mechanisms provides an opportunity for highly specific effects on gene regulation that depend on the cell type and on signals received from the cellular microenvironment.

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Complexity of redox regulation increases along the phylogenetic tree.

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Complex regulatory networks allow for a high degree of H₂O₂ biological plasticity.

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H₂O₂ modulates gene expression at all steps from transcription to protein synthesis.

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Fast response (s) is mediated by sensors with high H₂O₂ reactivity.

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Low reactivity H₂O₂ sensors may mediate slow (h) or localized H₂O₂ responses.

Multiple sclerosis: molecular mechanisms and therapeutic opportunities

The pathophysiology of multiple sclerosis (MS) involves several components: redox, inflammatory/autoimmune, vascular, and neurodegenerative. All of them are supported by the intertwined lines of evidence, and none of them should be written off. However, the exact mechanisms of MS initiation, its development, and progression are still elusive, despite the impressive pace by which the data on MS are accumulating. In this review, we will try to integrate the current facts and concepts, focusing on the role of redox changes and various reactive species in MS. Knowing the schedule of initial changes in pathogenic factors and the key turning points, as well as understanding the redox processes involved in MS pathogenesis is the way to enable MS prevention, early treatment, and the development of therapies that target specific pathophysiological components of the heterogeneous mechanisms of MS, which could alleviate the symptoms and hopefully stop MS. Pertinent to this, we will outline (i) redox processes involved in MS initiation; (ii) the role of reactive species in inflammation; (iii) prooxidative changes responsible for neurodegeneration; and (iv) the potential of antioxidative therapy.