Absence Of Reactive Oxygen Species Research Articles

Visualizing the 4D Impact of Gold Nanoparticles on DNA.

The genotoxicity of AuNPs has sparked a scientific debate, with one perspective attributing it to direct DNA damage and another to oxidative damage through reactive oxygen species (ROS) activation. This controversy poses challenges for the widespread use of AuNPs in biomedical applications. To address this debate, we employed four-dimensional atomic force microscopy (4DAFM) to examine the ability of AuNPs to damage DNA in vitro in the absence of ROS. To further examine whether the size and chemical coupling of these AuNPs are properties that control their toxicity, we exposed individual DNA molecules to three different types of AuNPs: small (average diameter = 10 nm), large (average diameter = 22 nm), and large conjugated (average diameter = 39 nm) AuNPs. We found that all types of AuNPs caused rapid (within minutes) and direct damage to the DNA molecules without the involvement of ROS. This research holds significant promise for advancing nanomedicines in diverse areas like viral therapy (including COVID-19), cancer treatment, and biosensor development for detecting DNA damage or mutations by resolving the ongoing debate regarding the genotoxicity mechanism. Moreover, it actively contributes to the continuous endeavors aimed at fully harnessing the capabilities of AuNPs across diverse biomedical fields, promising transformative healthcare solutions.

The natural compound from Garcinia bracteata mainly induces GSDME-mediated pyroptosis in esophageal cancer cells

BackgroundPyroptosis, an inflammatory form of programmed cell death (PCD), is reported to play important roles in the treatment of tumors. In our previous studies, we found that neobractatin (NBT), a caged prenylxanthone isolated from edible fruits of Garcinia bracteata C. Y. Wu ex Y. H. Li, showed anticancer effects against different cancer cells. However, the effect of NBT on pyroptosis is not well understood. PurposeThis study aims to investigate whether and how GSDME-mediated pyroptosis contributes to NBT-induced antitumor effects in esophageal cancer (EC) cells. MethodsCell viability assay and colony formation assay were used to determine the anticancer effects of NBT in esophageal cancer cells. Lactate dehydrogenase (LDH) release assay and microscopy imaging were used to detect the main characteristic of pyroptosis. CRISPR–Cas9 knockout and siRNA knockdown were performed to verify the roles of GSDME and caspase-3 in NBT-induced pyroptosis. Flow cytometry was used to measure the reactive oxygen species (ROS) level and cell apoptosis. The changes of related protein level were detected by Western blot. Furthermore, animal experiments were used to verify the in vivo effect of NBT. ResultsThe results showed that NBT reduced the viability of EC cells mainly through GSDME-mediated pyroptosis. Morphologically, NBT induced cell swelling and formed large bubbles emerging from plasma membrane in wild type EC cells. Furthermore, NBT induced the cleavage of GSDME by activating caspase-3 in EC cells. On the other hand, caspase-3 activated by NBT also induced apoptosis especially at high dosage. Knocking down GSDME switched NBT-induced cell death from mainly pyroptosis to apoptosis in vivo and in vitro. Mechanistic studies indicated that NBT led to accumulation of ROS, which then regulated the phosphorylation of both JNK and MEK/ERK. In the absence of ROS or caspase-3, NBT-induced pyroptosis and apoptosis were completely reversed. Moreover, NBT showed a significant antitumor effect in both the KYSE150 and GSDME knockout KYSE150-/- xenograft models by inducing pyroptosis and apoptosis, respectively. ConclusionOur results indicated that natural compound NBT could induce GSDME-mediated pyroptosis and apoptosis in esophageal cancer cells, making it a potential therapeutic drug in clinical treatment.

Absence of Interleukin-6 Protects Murine Bone Marrow Erythropoiesis Under Inflammation, in a Process Reversible By Iron Mediated Reactive Oxygen Species Upregulation

Inflammatory states seen in infections and chronic disorders are often characterized by a condition called anemia of Inflammation (AI). Using a mouse model of AI generated by a single injection of the heat killed pathogen Brucella abortus (BA), we have previously shown that mice lacking IL6 (IL6 -KO mice) exhibited protected erythropoiesis in the bone marrow (BM) and a faster recovery from anemia compared to controls. To study the mechanism of IL6 mediated improved erythropoiesis under AI, we investigated erythroid recovery in WT and IL6 -KO mice injected with BA. 72 hours following BA administration, both genotypes showed impaired BM erythropoiesis associated by a surge in inflammatory cytokines such as IFNγ and TNFα and a concurrent increase in mitochondrial ROS (reactive oxygen species), specifically superoxide (SO) in erythroid progenitors. Cytokines levels were normalized after 24 hours. However, during the second phase of erythroid recovery (10-14 days following BA treatment), mice showed a second surge of inflammatory cytokines. During this phase, IL6 -KO mice showed significantly improved BM erythropoiesis and normalization of ROS levels. We analyzed SO levels by Mitosox red, generic ROS production using the chloromethyl derivative of 2′,7′-dichlorofluorescin diacetate and total protein oxidation (by looking at total protein carbonylation) by Western blot. These results were in sharp contrast to WT animals which continued to show upregulated ROS, total protein oxidation and slackened erythroid recovery.Given the extensive association of iron overloading conditions and oxidative stress, we investigated the improved erythroid recovery within IL6 -KO mice in the context of increased iron absorption. We asked if and how BM erythropoiesis would change in IL6 -KO mice lacking Hepcidin (Hamp), a key iron regulatory hormone whose absence induces iron overload. In double knock out mice lacking both IL6 and Hamp (DKO), we observed an initial improved erythroid recovery in the BM, as indicated by increased number of total BM erythroid progenitors and reticulocytes, and improved RBC lifespan. However, all of these factors regressed after 10 days, with a simultaneous increase of cytokine production. The deterioration of erythropoiesis in the BM was accompanied by a concurrent increase in ROS. Of note, compared to non-treated mice, erythroid progenitors in the spleen of DKO-BA did not show increased ROS levels, and this was associated with an increased number of splenic erythroid progenitors and RBC. These results point to a potential role in the microenvironment in influencing erythropoiesis under inflammation. Furthermore, these results suggest that while lack of IL6 protects BM erythropoiesis, iron overload could antagonize it. In fact, iron overloaded IL6 -KO mice (with iron dextran) did show an impairment in BM erythroid recovery and upregulation of ROS, similarly to the DKO. Finally, we hypothesized that while there is a distinct positive correlation between upregulated ROS and weakened BM erythropoiesis, this comes into effect only in the context of inflammation. In other words, we speculated that some level of ROS upregulation is otherwise a physiological byproduct of erythropoietic stress associated with the onset of anemia. In line with this theory, we found that ROS levels were indeed upregulated in BM erythroid progenitors of phlebotomized animals. Our data suggests a model of erythroid recovery under AI wherein inflammation exacerbates ROS production triggered by stress erythropoiesis, and that this phenomenon exquisitely impairs BM erythropoiesis. This negative effect on BM erythropoiesis is mitigated by the absence of IL6, but the lack of IL6 mediated protective function is reversible under conditions of iron overload (Figure 1).Our results, in combination with the upregulation of TNFa, suggest the involvement of non-apoptotic ROS associated programmed cell death such as necroptosis or ferroptosis, which are under investigation. We also have preliminary data pointing to mechanism of increased erythroid iron uptake that could potentially contribute to oxidative stress under AI. With these additional studies, we hope to further characterize the mechanisms surrounding improved BM erythropoiesis in the absence of ROS and IL6. Our studies could potentially characterize cellular responses that can be targeted in conditions of inflammation for therapeutic benefits. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Efficacy of light-emitting diodes emitting 395, 405, 415, and 425 nm blue light for bacterial inactivation and the microbicidal mechanism

We investigated the bactericidal effects against Escherichia coli O157:H7 of light-emitting diodes (LEDs) emitting blue light of four different peak wavelengths ranging from 395 to 425 nm in water. Furthermore, we investigated inactivation in the presence of reactive oxygen species (ROS) scavengers to elucidate the contribution of bacterial inactivation. An aluminum chamber was constructed and coated in carbon to block exterior light, and a single blue light LED with a rear heat sink was attached to the chamber lid. Effective inactivation of the pathogen was observed for all blue light LED irradiation at 305, 405, 415, and 425 nm. The log-linear with shoulder and tail model and log-linear model described the survival of the bacteria after blue light LED treatments. Not just the effects of ROS but also photophysical effects were shown with the addition of mannitol, a ROS scavenger. The integrity of the cell membrane was damaged regardless of the presence of ROS, which indicates that photophysical effects were sufficient to induce damage to the cell membrane. In addition, activity of succinate-coenzyme Q reductase, which participates in respiratory metabolism to generate energy, decreased in the absence of ROS and decreased further in the presence of ROS.

NRF2 preserves genomic integrity by facilitating ATR activation and G2 cell cycle arrest.

Nuclear factor erythroid 2-related factor 2 (NRF2) is a well-characterized transcription factor that protects cells against oxidative and electrophilic stresses. Emerging evidence has suggested that NRF2 protects cells against DNA damage by mechanisms other than antioxidation, yet the mechanism remains poorly understood. Here, we demonstrate that knockout of NRF2 in cells results in hypersensitivity to ionizing radiation (IR) in the presence or absence of reactive oxygen species (ROS). Under ROS scavenging conditions, induction of DNA double-strand breaks (DSBs) increases the NRF2 protein level and recruits NRF2 to DNA damage sites where it interacts with ATR, resulting in activation of the ATR–CHK1–CDC2 signaling pathway. In turn, this leads to G2 cell cycle arrest and the promotion of homologous recombination repair of DSBs, thereby preserving genome stability. The inhibition of NRF2 by brusatol increased the radiosensitivity of tumor cells in xenografts by perturbing ATR and CHK1 activation. Collectively, our results reveal a novel function of NRF2 as an ATR activator in the regulation of the cellular response to DSBs. This shift in perspective should help furnish a more complete understanding of the function of NRF2 and the DNA damage response.

Synthesis of new hetero-arylidene-9(10H)-anthrone derivatives and their biological evaluation.

New hetero-arylidene-9(10H)-anthrone derivatives (1) were synthesized from reaction of 1,2-dimethyl-3-alkyl imidazolium salts (2) and 9-anthracenecarboxaldehyde. Ion exchange of the anion with dioctyl sulfosuccinate and lithium bis(trifluoromethanesulfonyl)imide led to the preparation of other derivatives. The antiproliferative effect of the compounds was evaluated in human ovarian (A2780) and colorectal (HCT116) carcinoma cell lines and in normal primary human fibroblasts. Compound 1 presented an antiproliferative effect related to the imidazolium pattern of substitution with compounds having a decyl group at the R-position (1c and 3c) showing the highest cytotoxic activities in all cell lines independently of the counter ion. Compounds 1b and 1c internalize A2780 cancer cells via a passive or an active transport, respectively, inducing A2780 cell death via an extrinsic apoptosis (1b) or intrinsic apoptosis and oncosis (1c). The localization of both compounds in the cytoplasm coupled to the absence of reactive oxygen species (ROS) induction suggest that the mechanisms of toxicity might be different than those of other anthracyclines currently used in chemotherapy.

Human mast cells exhibit an individualized pattern of antimicrobial responses.

IntroductionMast cells (MCs) are tissue‐resident immune cells implicated in antibacterial responses. These include chemokine secretion, degranulation, and the release of mast cell‐extracellular traps, which are primarily dependent on reactive oxygen species (ROS) production. Our study investigated whether human mast cells (hMCs) develop individual response patterns to bacteria located at different tissue sites: Escherichia coli (gut commensal), Listeria monocytogenes (foodborne intracellular pathogen), Staphylococcus aureus (skin commensal and opportunistic pathogen), and Streptococcus pneumoniae (upper respiratory tract commensal and lung pathogen).MethodsAfter live bacteria exposure, hMCs were analyzed by a combined flow cytometry assay for degranulation, ROS production, DNA externalization, and for β‐hexosaminidase, chemokine, and prostaglandin release.Results L. monocytogenes induced hMC degranulation, IL‐8 and MCP‐1 release coupled with DNA externalization in a novel hMC ROS independent manner. In contrast, S. pneumoniae caused ROS production without DNA release and degranulation. E. coli induced low levels of hMC degranulation combined with interleukin 8 and MCP‐1 secretion and in the absence of ROS and DNA externalization. Finally, S. aureus induced hMCs prostaglandin D2 release and DNA release selectively. Our findings demonstrate a novel hMC phenomenon of DNA externalization independent of ROS production. We also showed that ROS production, degranulation, DNA externalization, and mediator secretion occur as independent immune reactions in hMCs upon bacterial encounter and that hMCs contribute to bacterial clearance.ConclusionsThus, hMCs exhibit a highly individualized pattern of immune response possibly to meet tissue requirements and regulate bacteria coexistence vs defense.

Synthesis, characterization and evaluation of multi sensitive nanocarriers by using the layer by layer method

HypothesisNowadays nanomedicine appears to be the most promising field in the area of nanotechnology. Diseases such as cancer, which lack of early diagnosis and therapy, are now able to be faced up via small nanoscale objects characterized by unique physicochemical characteristics. Nanocarriers have been investigated in the last years as a result of their ability to selectively target the diseased area. The present work deals with multi-sensitive hollow polymeric nanoformulations with well-tuned size, shape and cargo loading. ExperimentsThe synthetic route of biocompatible polymeric drug delivery systems consists of five steps. In the first step the core of methacrylic acid (MAA) was fabricated and then in the second step the first temperature-sensitive layer was added. An additional layer, the pH sensitive, was synthesized in the third step and last, in the fourth step the redox sensitive shell was fabricated. The layers were synthesized by distillation precipitation co-polymerization via layer by layer methodology. In the final step, the core-shell structures were modified in order to encapsulate chemotherapeutic agents, such as daunorubicin (DNR) and Cisplatin. The loading capacity (% L.C.) and encapsulation efficiency (% E.E.) percentages were measured by the standard curve methodology. Furthermore, the releasing properties of the multi responsive nanocarriers were investigated, applying the above already mentioned approach. Finally, cell migration and cell viability studies were performed in human breast epithelial cancer MCF-7 and normal human keratinocyte NCTC 2544 cell lines both in the presence and absence of reactive oxygen species (ROS) by using scavenging agents in order to evaluate the cell proliferation efficiency along with the apoptotic effect induced by these multi-sensitive drug delivery systems. FindingsTo this end, the hollow nanospheres presented an excellent release behaviour with DNR and Cisplatin under acidic environment, high temperature as well as in the presence of glutathione. Moreover, the cell proliferation assay in conjunction to the wound-healing assays indicated that the hollow NCs are non-toxic both in healthy and cancer cells in contrary to the loaded ones.

A comparison of the photolytic and photocatalytic degradation of fluvastatin

Fluvastatin, a commonly used cholesterol-lowering drug, has attracted considerable attention because of its adverse effects on human beings. Photolysis and ZnIn2S4 photocatalysis of fluvastatin under UV–Vis irradiation were compared based on analysis of reactive oxygen species (ROS), degradation pathways, and toxicity evaluation. The removal rates of fluvastatin by photolysis and photocatalysis were 71.07% and 99.79%, respectively. Photolytic degradation of fluvastatin was conducted in the absence of ROS, whereas O2− played a vital role and OH played an auxiliary role during the photocatalytic process. The photolytic degradation of fluvastatin was achieved through cleavage of the CC, CN, and CC bonds. Because of the limited photon energy, photolytic products with stable structure did not decompose easily, which resulted in chemical oxygen demand (COD) removal rate of the photolytic system only 15.62%. The photocatalytic degradation of fluvastatin was achieved through direct cleavage of the chemical bonds under the synergistic oxidation of O2− and OH, and the hydroxylation reaction under OH attack. The COD removal rate of the photocatalytic system reached 43.05%. The photocatalytic samples were slightly less toxic than fluvastatin, whereas the photolytic samples were more toxic than fluvastatin. Therefore, the toxicity of the photolytic samples was significantly higher than that of the photocatalytic samples. Photocatalysis was an effective way for mitigation and elimination of harm of statins to the environment than photolysis.

YO-10 - ROS is the boss

The production of reactive oxygen species (ROS) via the oxidative burst has been connected with promotion of inflammation and tissue damage, but in recent years has been implicated in regulation of inflammation. We investigated the effects of ROS on the murine model of lupus and in patients (SLE). The aim of this project was to elucidate the impact of the oxidative burst on the development of lupus-like autoimmunity. Lupus was induced by i.p. injection of pristane oil. Ex vivo phagocytosis assays were deployed to assess the uptake of cell debris in ROS deficient mice. The formation of neutrophil extracellular traps (NETs) was analysed by immune fluorescence microscopy. ROS activators were injected into mice to investigate the possible beneficial clinical effects on lupus pathology. The absence of ROS gives rise to dramatically exacerbated lupus. Aberrant phagocytosis in ROS-deficient animals leading to production of inflammatory mediators, accompanied by diminished pristane-induced but higher spontaneous formation of NETs could be responsible for this phenotype. Treatment with NOX2 agonists ameliorated the clinical course in mice, while application of a ROS scavenger worsened disease outcome. A fine-tuned balance of ROS-production is necessary to prevent autoimmunity and to avert the development of lupus in mice and men.

Long-term antibacterial characteristics and cytocompatibility of titania nanotubes loaded with Au nanoparticles without photocatalytic effects

Au nanoparticles (NPs) can endow titania nanotubes (Au@TiO2-NT) with light-independent antibacterial properties which bode well for in vivo application because of the dark environment inside tissues. In this work, the long-term antibacterial bactericidal properties and cytocompatibility of Au@TiO2-NT without photocatalytic effects are studied in details. The materials exhibit antibacterial effects against Staphylococcus aureus according to antibacterial tests carried out for a total time of 21 days, which are normally long enough for early stage tissue healing after surgery. In addition, adhesion and proliferation of MC3T3-E1 osteoblasts on Au@TiO2-NT reveal cytocompatibility comparable to that of TiO2-NT. No reactive oxygen species (ROS) are detected from either the bacteria or MC3T3-E1 cells cultured on the Au@TiO2-NT surface. The absence of ROS, long-term antibacterial properties, and cytocompatibility make Au@TiO2-NT promising biomaterials in orthopedic devices and implants.

A Tumor Cell-Selective Inhibitor of Mitogen-Activated Protein Kinase Phosphatases Sensitizes Breast Cancer Cells to Lymphokine-Activated Killer Cell Activity.

Dual specificity mitogen-activated protein kinase (MAPK) phosphatases [dual specificity phosphatase/MAP kinase phosphatase (DUSP-MKP)] have been hypothesized to maintain cancer cell survival by buffering excessive MAPK signaling caused by upstream activating oncogenic products. A large and diverse body of literature suggests that genetic depletion of DUSP-MKPs can reduce tumorigenicity, suggesting that hyperactivating MAPK signaling by DUSP-MKP inhibitors could be a novel strategy to selectively affect the transformed phenotype. Through in vivo structure-activity relationship studies in transgenic zebrafish we recently identified a hyperactivator of fibroblast growth factor signaling [(E)-2-benzylidene-5-bromo-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one (BCI-215)] that is devoid of developmental toxicity and restores defective MAPK activity caused by overexpression of DUSP1 and DUSP6 in mammalian cells. Here, we hypothesized that BCI-215 could selectively affect survival of transformed cells. In MDA-MB-231 human breast cancer cells, BCI-215 inhibited cell motility, caused apoptosis but not primary necrosis, and sensitized cells to lymphokine-activated killer cell activity. Mechanistically, BCI-215 induced rapid and sustained phosphorylation of extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK) in the absence of reactive oxygen species, and its toxicity was partially rescued by inhibition of p38 but not JNK or ERK. BCI-215 also hyperactivated MKK4/SEK1, suggesting activation of stress responses. Kinase phosphorylation profiling documented BCI-215 selectively activated MAPKs and their downstream substrates, but not receptor tyrosine kinases, SRC family kinases, AKT, mTOR, or DNA damage pathways. Our findings support the hypothesis that BCI-215 causes selective cancer cell cytotoxicity in part through non-redox-mediated activation of MAPK signaling, and the findings also identify an intersection with immune cell killing that is worthy of further exploration.

The Transcription Factor Nrf2 Protects Angiogenic Capacity of Endothelial Colony-Forming Cells in High-Oxygen Radical Stress Conditions.

Background Endothelial colony forming cells (ECFCs) have shown a promise in tissue engineering of vascular constructs, where they act as endothelial progenitor cells. After implantation, ECFCs are likely to be subjected to elevated reactive oxygen species (ROS). The transcription factor Nrf2 regulates the expression of antioxidant enzymes in response to ROS. Methods Stable knockdown of Nrf2 and Keap1 was achieved by transduction with lentiviral shRNAs; activation of Nrf2 was induced by incubation with sulforaphane (SFN). Expression of Nrf2 target genes was assessed by qPCR, oxidative stress was assessed using CM-DCFDA, and angiogenesis was quantified by scratch-wound and tubule-formation assays Results. Nrf2 knockdown led to a reduction of antioxidant gene expression and increased ROS. Angiogenesis was disturbed after Nrf2 knockdown even in the absence of ROS. Conversely, angiogenesis was preserved in high ROS conditions after knockdown of Keap1. Preincubation of ECFCs with SFN reduced intracellular ROS in the presence of H2O2 and preserved scratch-wound closure and tubule-formation. Results Nrf2 knockdown led to a reduction of antioxidant gene expression and increased ROS. Angiogenesis was disturbed after Nrf2 knockdown even in the absence of ROS. Conversely, angiogenesis was preserved in high ROS conditions after knockdown of Keap1. Preincubation of ECFCs with SFN reduced intracellular ROS in the presence of H2O2 and preserved scratch-wound closure and tubule-formation. Conclusion The results of this study indicate that Nrf2 plays an important role in the angiogenic capacity of ECFCs, particularly under conditions of increased oxidative stress. Pretreatment of ECFCs with SFN prior to implantation may be a protective strategy for tissue-engineered constructs or cell therapies.

106 - ROS Ameriolates the Clinical Course of Murine Lupus

The production of reactive oxygen species (ROS) via the oxidative burst has in the traditional view been connected with promotion of inflammation and tissue damage, but has in recent years also been implicated in regulation of inflammation and protection from autoimmunity. We have investigated the effects of ROS on the autoimmunity in a mouse model of lupus and in patients with systemic lupus erythematosus (SLE). Aims The aim of this project was to elucidate the impact of the oxidative burst on the development of lupus-like autoimmunity in wild type and Ncf1** mice which carry a point mutation in one of the subunits of the phagocyte NADPH oxidase 2 complex that abrogates ROS-production. Lupus was induced by intraperitoneal injection of 0.5 ml pristane oil and the clinical course was compared by analysis of serological markers and organ involvement. Ex vivo phagocytosis assays and flow cytometry were deployed to assess uptake of cell debris in ROS deficient mice. The formation of neutrophil extracellular traps (NETs) was analysed by immune fluorescence microscopy. Potential activators of ROS production were injected into mice to investigate the possible beneficial clinical effects on lupus pathology. Results Our results show that the absence of ROS in Ncf1** mice gives rise to dramatically exacerbated lupus. Aberrant phagocytosis in ROS-deficient animals leading to production of inflammatory mediators, accompanied by diminished pristane-induced but higher spontaneous formation of NETs could be responsible for this phenotype. Treatment of pristane-induced lupus with NOX2 agonists ameliorated the clinical course in BALB/c mice, while application of a ROS scavenger worsened disease outcome. Further, downstream nrf2 signalling was decreased in Ncf1** mice. Patients with SLE showed similar aberrant phagocytosis as in murine lupus, and were characterized by higher spontaneous formation of NETs. A fine-tuned balance of ROS-production is necessary to prevent autoimmunity and to avert the development of lupus in mice and men.

Reactive oxygen homeostasis – the balance for preventing autoimmunity

Being mainly known for their role in the antimicrobial defense and collateral damage they cause in tissues as agents of oxidative stress, reactive oxygen species were considered "the bad guys" for decades. However, in the last years it was shown that the absence of reactive oxygen species can lead to the development of immune-mediated inflammatory diseases. Animal models of lupus, arthritis and psoriasis revealed reactive oxygen species-deficiency as a potent driver of pathogenesis. On the contrary, in chronic stages oxidative stress can still contribute to progression of inflammation. It seems that a neatly adjusted redox balance is necessary to sustain an immune state that both prevents the development of overt autoimmunity and attenuates chronic stages of disease.

NADPH oxidase-derived superoxide provides a third signal for CD4 T cell effector responses

Abstract Efficient T cell immune activation requires a synergistic interaction between innate immune-derived reactive oxygen species (ROS) and pro-inflammatory cytokines. Our laboratory previously demonstrated that in the absence of NADPH oxidase (NOX)-derived superoxide, autoreactive T cell responses were profoundly compromised. To examine the role of ROS deficiency on antigen-specific T cells in a non-autoimmune setting and further test the hypothesis that Th1 T cell responses would be diminished in the absence of ROS, we generated the OT-II.Ncf1m1J mouse containing superoxide-deficient, OVA323-339-specific CD4 T cells. Stimulation of OT-II.Ncf1m1J elicited a 4-fold decrease in IFN-γ (p<0.05), concomitant with 2-fold reductions in CD4 T cell-derived IL-12Rβ2 and T-bet, required for Th1 activation. Th1 responses elicited by OVA323-339 stimulation were redox-sensitive, as addition of exogenous superoxide to OT-II.Ncf1m1J CD4 T cells restored IFN-γ synthesis and IL-12 signaling to approximately OT-II CD4 T cell levels. Conversely, Th1 responses were curbed in wild type OT-II T cells via free radical dissipation with a superoxide dismutase mimetic. This data highlights the importance of NOX-derived ROS in providing a third signal for adaptive immune maturation by modulating IL-12 signaling and may represent a promising therapeutic strategy in curbing CD4 T cell autoreactivity.

Moonlight-like proteins of the cell wall protect sessile cells of Candida from oxidative stress

Biofilms of Candida species are associated with high morbidity and hospital mortality. Candida forms biofilms by adhering to human host epithelium through cell wall proteins (CWP) and simultaneously neutralizing the reactive oxygen species (ROS) produced during the respiratory burst by phagocytic cells. The purpose of this paper is to identify the CWP of Candida albicans, Candida glabrata, Candida krusei and Candida parapsilosis expressed after exposure to different concentrations of H2O2 using a proteomic approach. CWP obtained from sessile cells, both treated and untreated with the oxidizing agent, were resolved by one and two-dimensional (2D-PAGE) gels and identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Some of these proteins were identified and found to correspond to moonlighting CWP such as: (i) glycolytic enzymes, (ii) heat shock, (iii) OSR proteins, (iv) general metabolic enzymes and (v) highly conserved proteins, which are up- or down-regulated in the presence or absence of ROS. We also found that the expression of these CWP is different for each Candida species. Moreover, RT-PCR assays allowed us to demonstrate that transcription of the gene coding for Eno1, one of the moonlight-like CWP identified in response to the oxidant agent, is differentially regulated. To our knowledge this is the first demonstration that, in response to oxidative stress, each species of Candida, differentially regulates the expression of moonlighting CWP, which may protect the organism from the ROS generated during phagocytosis. Presumptively, these proteins allow the pathogen to adhere and form a biofilm, and eventually cause invasive candidiasis in the human host. We propose that, in addition to the antioxidant mechanisms present in Candida, the moonlighting CWP also confer protection to these pathogens from oxidative stress.

Oxidative degradation of N(ε)-fructosylamine-substituted peptides in heated aqueous systems.

Glycation, or non-enzymatic glycosylation, is a common protein modification formed by reactions between reducing sugars (i.e. aldoses and ketoses) with protein amino groups. Resulting Amadori and Heyns compounds, respectively, can be oxidatively degraded yielding a structurally heterogeneous group of advanced glycation end-products. We have studied this process in aqueous conditions at 95 °C in terms of appearing products and their formation kinetics in the presence or absence of reactive oxygen species (ROS)-generating systems (iron(II) sulfate). RP-HPLC-ESI-MS revealed 20 products, 12 of which were confirmed after synthesis by identical retention times and fragmentation patterns. These products accumulated during the incubation period of 4 h (N(ε)-carboxymethyl-, N(ε)-formyl- and N(ε)-methyl lysine) or appeared intermediately (2-aminoadipic semialdehyde, N(ε)-ethanalyl lysine). Acidic and basic amino acid residues near the glycation site and elevated ROS levels in the reaction mixture had significant effects on both product formation and degradation kinetics.

Moving forward with reactive oxygen species involvement in antimicrobial lethality.

Support for the contribution of reactive oxygen species (ROS) to antimicrobial lethality has been refined and strengthened. Killing by diverse antimicrobials is enhanced by defects in genes that protect against ROS, inhibited by compounds that block hydroxyl radical accumulation, and is associated with surges in intracellular ROS. Moreover, support has emerged for a genetic pathway that controls the level of ROS. Since some antimicrobials kill in the absence of ROS, ROS must add to, rather than replace, known killing mechanisms. New work has addressed many of the questions concerning the specificity of dyes used to detect intracellular ROS and the specificity of perturbations that influence ROS surges. However, complexities associated with killing under anaerobic conditions remain to be resolved. Distinctions among primary lesion formation, resistance, direct lesion-mediated killing and a self-destructive stress response are discussed to facilitate efforts to potentiate ROS-mediated bacterial killing and improve antimicrobial efficacy.

An intracellular redox sensor for reactive oxygen species at the M3‐M4 linker of GABAAρ1 receptors

Reactive oxygen species (ROS) are normally involved in cell oxidative stress but also play a role as cellular messengers in redox signalling; for example, modulating the activity of neurotransmitter receptors and ion channels. However, the direct actions of ROS on GABAA receptors were not previously demonstrated. In the present work, we studied the effects of ROS on GABAA ρ1 receptor function. GABAA ρ1 receptors were expressed in oocytes and GABA-evoked responses electrophysiologically recorded in the presence or absence of ROS. Chemical protection of cysteines by selective sulfhydryl reagents and site-directed mutagenesis studies were used to identify protein residues involved in ROS actions. GABAA ρ1 receptor-mediated responses were significantly enhanced in a concentration-dependent and reversible manner by H₂O₂. Potentiating effects were attenuated by a free radical scavenger, lipoic acid or an inhibitor of the Fenton reaction, deferoxamine. Each ρ1 subunit contains only three cysteine residues, two extracellular at the Cys-loop (C¹⁷⁷ and C¹⁹¹) and one intracellular (C³⁶⁴) at the M3-M4 linker. Mutant GABAA ρ1 receptors in which C³⁶⁴ was exchanged by alanine were completely insensitive to modulation, implying that this site, rather than a cysteine in the Cys-loop, is essential for ROS modulation. Our results show that the function of GABAA ρ1 receptors is enhanced by ROS and that the intracellular C³⁶⁴ is the sensor for ROS actions.