Project description:Prevention of phenotype switching of vascular smooth muscle cells is an important determinant of normal vascular physiology. Hydrogen peroxide (H2O2) promotes osteogenic differentiation of vascular smooth muscle cells through expression of Runt related transcription factor 2 (Runx2). In this study, an increase in dietary NaCl increased endothelial H2O2 generation through NOX4, a NAD(P)H oxidase. The production of H2O2 was sufficient to increase Runx2, osteopontin and osteocalcin in adjacent vascular smooth muscle cells from control littermate mice but was inhibited in mice lacking endothelial Nox4. A vascular smooth muscle cell culture model confirmed the direct involvement of the activation of protein kinase B (Akt) with inactivation of FoxO1 and FoxO3a observed in the control mice on the high NaCl diet. The present study also showed a reduction of catalase activity in aortas during high NaCl intake. The findings demonstrated an interesting cell-cell communication in the vascular wall that was initiated with H2O2 production by endothelium and was regulated by dietary NaCl intake. A better understanding of how dietary salt intake alters vascular biology may improve treatment of vascular disease that involves activation of Runx2.
Project description:Chronic granulomatous disease (CGD) is caused by mutations in genes that encode the NADPH-oxidase and result in a failure of phagocytic cells to produce reactive oxygen species (ROS) via this enzyme system. Patients with CGD are highly susceptible to infections and often suffer from inflammatory disorders; the latter occurs in the absence of infection and correlates with the spontaneous production of inflammatory cytokines. This clinical feature suggests that NADPH-oxidase-derived ROS are not required for, or may even suppress, inflammatory processes. Experimental evidence, however, implies that ROS are in fact required for inflammatory cytokine production. By using a myeloid cell line devoid of a functional NADPH-oxidase and primary CGD cells, we analyzed intracellular oxidants, signs of oxidative stress, and inflammatory cytokine production. Herein, we demonstrate that phagocytes lacking a functional NADPH-oxidase, namely primary CGD phagocytes and a gp91phox-deficient cell line, display elevated levels of ROS derived from mitochondria. Accordingly, these cells, despite lacking the major source of cellular ROS, display clear signs of oxidative stress, including an induced expression of antioxidants and altered oxidation of cell surface thiols. These observed changes in redox state were not due to abnormalities in mitochondrial mass or membrane integrity. Finally, we demonstrate that increased mitochondrial ROS enhanced phosphorylation of ERK1/2, and induced production of IL8, findings that correlate with previous observations of increased MAPK activation and inflammatory cytokine production in CGD cells. Our data show that elevated baseline levels of mitochondria-derived oxidants lead to the counter-intuitive observation that CGD phagocytes are under oxidative stress and have enhanced MAPK signaling, which may contribute to the elevated basal production of inflammatory cytokines and the sterile inflammatory manifestations in CGD.
Project description:Vanillic acid is a widely used food additive (flavouring agent, JECFA number: 959) with many reported beneficial biological effects. The same is true for its ester derivative (methyl vanillate, JECFA number: 159). Based on the increasing evidence that diapocynin, the dimer of apocynin (NADPH oxidase inhibitor), has some improved pharmacological properties compared to its monomer, here the dimer of methyl vanillate (MV), i.e., methyl divanillate (dimer of methyl vanillate, DMV) was synthesized and studied in the context of its redox properties and binding affinity with human serum albumin (HSA). We found that the antioxidant potency of DMV was significantly increased compared to MV. In this regard, the reduction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical by DMV was 30-fold more effective compared to MV. Ferric ion reduction was 4-fold higher and peroxyl radical reduction was 2.7-fold higher. The interaction with HSA was significantly improved (Stern-Vomer constants, 3.8 × 105 mol-1 L and 2.3 × 104 mol-1 L, for DMV and MV, respectively). The complexation between DMV and HSA was also evidenced by induced circular dichroism (ICD) signal generation in the former due to its fixation in the asymmetric protein pocket. Density-functional calculations (TD-DFT) showed that the ICD spectrum was related to a DMV conformation bearing a dihedral angle of approximately -60°. Similar dihedral angles were obtained in the lowest and most populated DMV cluster poses obtained by molecular docking simulations. The computational studies and experimental displacement studies revealed that DMV binds preferentially at site I. In conclusion, besides being a powerful antioxidant, DMV is also a strong ligand of HSA. This is the first study on the chemical and biophysical properties of DMV, a compound with potential beneficial biological effects.
Project description:The leukocyte NADPH oxidase 2 (NOX2) plays a key role in pathogen killing and immunoregulation. Genetic defects in NOX2 result in chronic granulomatous disease (CGD), associated with microbial infections and inflammatory disorders, often involving the lung. Alveolar macrophages (AMs) are the predominant immune cell in the airways at steady state, and limiting their activation is important, given the constant exposure to inhaled materials, yet the importance of NOX2 in this process is not well understood. In this study, we showed a previously undescribed role for NOX2 in maintaining lung homeostasis by suppressing AM activation, in CGD mice or mice with selective loss of NOX2 preferentially in macrophages. AMs lacking NOX2 had increased cytokine responses to Toll-like receptor-2 (TLR2) and TLR4 stimulation ex vivo. Moreover, between 4 and 12 week of age, mice with global NOX2 deletion developed an activated CD11bhigh subset of AMs with epigenetic and transcriptional profiles reflecting immune activation compared with WT AMs. The presence of CD11bhigh AMs in CGD mice correlated with an increased number of alveolar neutrophils and proinflammatory cytokines at steady state and increased lung inflammation after insults. Moreover, deletion of NOX2 preferentially in macrophages was sufficient for mice to develop an activated CD11bhigh AM subset and accompanying proinflammatory sequelae. In addition, we showed that the altered resident macrophage transcriptional profile in the absence of NOX2 is tissue specific, as those changes were not seen in resident peritoneal macrophages. Thus, these data demonstrate that the absence of NOX2 in alveolar macrophages leads to their proinflammatory remodeling and dysregulates alveolar homeostasis.
Project description:Melatonin (MT) is a crucial hormone that controls and positively regulates plant growth under abiotic stress, but the biochemical and physiological processes of the combination of melatonin seed initiation and exogenous spray treatments and their effects on maize germination and seedling salt tolerance are not well understood. Consequently, in this research, we utilized the maize cultivars Zhengdan 958 (ZD958) and Demeiya 1 (DMY1), which are extensively marketed in northeastern China's high-latitude cold regions, to reveal the modulating effects of melatonin on maize salinity tolerance by determining the impacts of varying concentrations of melatonin on maize seedling growth characteristics, osmoregulation, antioxidant systems, and gene expression. The findings revealed that salt stress (100 mM NaCl) significantly inhibited maize seed germination and seedling development, which resulted in significant increases in the H2O2 and O2- content and decreases in the antioxidant enzyme activity and photosynthetic pigment content in maize seedlings. However, exogenous melatonin considerably reduced the development inhibition caused by salt stress in maize seedlings. Moreover, exogenous melatonin alleviated NaCl-induced membrane damage and oxidative stress, and reduced Na+ content and excessively large quantities of reactive oxygen species (ROS). In addition, exogenous melatonin increased antioxidant enzyme activity and the expression of the antioxidant enzyme genes ZmSOD4, ZmCAT2, and ZmAPX2. This study demonstrates the potential role of combined melatonin seed initiation and foliar spray treatments in mitigating the detrimental effects of salt stress on maize growth, giving a theoretical foundation to future research on the possible advantages of exogenous regulating chemicals in attaining sustainable production in salt-alkaline soils.
Project description:MYCN amplification is an independent poor prognostic factor in patients with high-risk neuroblastoma (NB). Further exploring the molecular regulatory mechanisms in MYCN-amplified NB will help to develop novel therapy targets. In this study, methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) was identified as the differentially expressed gene (DEG) highly expressed in MYCN-amplified NB, and it showed a positive correlation with MYCN and was associated with a poor prognosis of NB patients. Knockdown of MTHFD1 inhibited proliferation and migration, and induced apoptosis of NB cells in vitro. Mouse model experiments validated the tumorigenic effect of MTHFD1 in NB in vivo. In terms of the mechanism, ChIP-qPCR and dual-luciferase reporter assays demonstrated that MTHFD1 was directly activated by MYCN at the transcriptional level. As an important enzyme in the folic acid metabolism pathway, MTHFD1 maintained the NADPH redox homeostasis in MYCN-amplified NB. Knockdown of MTHFD1 reduced cellular NADPH/NADP+ and GSH/GSSG ratios, increased cellular reactive oxygen species (ROS) and triggered the apoptosis of NB cells. Moreover, genetic knockdown of MTHFD1 or application of the anti-folic acid metabolism drug methotrexate (MTX) potentiated the anti-tumor effect of JQ1 both in vitro and in vivo. Taken together, MTHFD1 as an oncogene is a potential therapeutic target for MYCN-amplified NB. The combination of MTX with JQ1 is of important clinical translational significance for the treatment of patients with MYCN-amplified NB.
Project description:ObjectiveTo determine the functional significance of physiological reactive oxygen species (ROS) levels in endothelium-dependent nitric oxide (NO)-mediated coronary vasodilatation.Methods and resultsEndothelium-derived NO is important in regulating coronary vascular tone. Excess ROS have been shown to reduce NO bioavailability, resulting in endothelial dysfunction and coronary diseases. NADPH oxidase is a major source of ROS in endothelial cells (ECs). By using lucigenin-based superoxide production and dichlorfluorescein diacetate (DCFH-DA) fluorescence-activated cell sorter assays, we found that mouse heart ECs from NADPH oxidase-knockdown (p47(phox-/-)) animals have reduced NADPH oxidase activity (>40%) and ROS levels (>30%) compared with wild-type mouse heart ECs. Surprisingly, a reduction in ROS did not improve coronary vasomotion; rather, endothelium-dependent vascular endothelial growth factor-mediated coronary vasodilatation was reduced by greater than 50% in p47(phox-/-) animals. Western blots and L-citrulline assays showed a significant reduction in Akt/protein kinase B (PKB) and endothelial NO synthase phosphorylation and NO synthesis, respectively, in p47(phox-/-) coronary vessels and mouse heart ECs. Adenoviral expression of constitutively active endothelial NO synthase restored vascular endothelial growth factor-mediated coronary vasodilatation in p47(phox-/-) animals.ConclusionsEndothelium-dependent vascular endothelial growth factor regulation of coronary vascular tone may require NADPH oxidase-derived ROS to activate phosphatidylinositol 3-kinase-Akt-endothelial NO synthase axis.
Project description:Brassinosteroids (BRs) have been shown to induce hydrogen peroxide (H(2)O(2)) accumulation, and BR-induced H(2)O(2) up-regulates antioxidant defence systems in plants. However, the mechanisms by which BR-induced H(2)O(2) regulates antioxidant defence systems in plants remain to be determined. In the present study, the role of ZmMPK5, a mitogen-activated protein kinase, in BR-induced anitioxidant defence and the relationship between the activation of ZmMPK5 and H(2)O(2) production in BR signalling were investigated in leaves of maize (Zea mays) plants. BR treatment activated ZmMPK5, induced apoplastic and chloroplastic H(2)O(2) accumulation, and enhanced the total activities of antioxidant enzymes. Such enhancements were blocked by pre-treatment with mitogen-activated protein kinase kinase (MAPKK) inhibitors and H(2)O(2) inhibitors or scavengers. Pre-treatment with MAPKK inhibitors substantially arrested the BR-induced apoplastic H(2)O(2) production after 6 h of BR treatment, but did not affect the levels of apoplastic H(2)O(2) within 1 h of BR treatment. BR-induced gene expression of NADPH oxidase was also blocked by pre-treatment with MAPKK inhibitors and an apoplastic H(2)O(2) inhibitor or scavenger after 120 min of BR treatment, but was not affected within 30 min of BR treatment. These results suggest that the BR-induced initial apoplastic H(2)O(2) production activates ZmMPK5, which is involved in self-propagation of apoplastic H(2)O(2) via regulation of NADPH oxidase gene expression in BR-induced antioxidant defence systems.
Project description:The plant microbiota consists of a multitude of microorganisms that can affect plant health and fitness. However, it is currently unclear how the plant shapes its leaf microbiota and what role the plant immune system plays in this process. Here, we evaluated Arabidopsis thaliana mutants with defects in different parts of the immune system for an altered bacterial community assembly using a gnotobiotic system. While higher-order mutants in receptors that recognize microbial features and in defence hormone signalling showed substantial microbial community alterations, the absence of the plant NADPH oxidase RBOHD caused the most pronounced change in the composition of the leaf microbiota. The rbohD knockout resulted in an enrichment of specific bacteria. Among these, we identified Xanthomonas strains as opportunistic pathogens that colonized wild-type plants asymptomatically but caused disease in rbohD knockout plants. Strain dropout experiments revealed that the lack of RBOHD unlocks the pathogenicity of individual microbiota members driving dysbiosis in rbohD knockout plants. For full protection, healthy plants require both a functional immune system and a microbial community. Our results show that the NADPH oxidase RBOHD is essential for microbiota homeostasis and emphasizes the importance of the plant immune system in controlling the leaf microbiota.
Project description:Many metabolic diseases disrupt endoplasmic reticulum (ER) homeostasis, but little is known about how metabolic activity is communicated to the ER. Here, we show in hepatocytes and other metabolically active cells that decreasing the availability of substrate for the tricarboxylic acid (TCA) cycle diminished NADPH production, elevated glutathione oxidation, led to altered oxidative maturation of ER client proteins, and attenuated ER stress. This attenuation was prevented when glutathione oxidation was disfavored. ER stress was also alleviated by inhibiting either TCA-dependent NADPH production or Glutathione Reductase. Conversely, stimulating TCA activity increased NADPH production, glutathione reduction, and ER stress. Validating these findings, deletion of the Mitochondrial Pyruvate Carrier-which is known to decrease TCA cycle activity and protect the liver from steatohepatitis-also diminished NADPH, elevated glutathione oxidation, and alleviated ER stress. Together, our results demonstrate a novel pathway by which mitochondrial metabolic activity is communicated to the ER through the relay of redox metabolites.