DNA damage by nitric oxide

Synergistic antibacterial and antifouling wound dressings: Integration of photothermal-activated no release and zwitterionic surface modification

Addressing the pervasive issue of bacteria and biofilm infections is crucial in the development of advanced antifouling wound dressings. In this study, a novel wound healing treatment using sulfobetaine (SBMA) decorated electrospun fibrous membrane based on polycaprolactone (PCL)/nitric oxide (NO) donors was developed. The fabrication involved a dual strategy, first integrating NO donors into mesoporous polydopamine (MPDA) and complexed with PCL/PEI to electrospin nanofibers. The fibrous membrane exhibited a potent antibacterial response upon irradiation at 808 nm, owing to a combination of NO and photothermal effect that effectively targets bacteria and disrupts biofilms. Surface functionalization of the membrane with PEI allowed for the attachment of SBMA via Michael addition, fabricating a zwitterionic surface, which significantly hinders protein adsorption and reduces biofilm formation on the wound dressing. In vitro and in vivo assessments confirmed the rapid bactericidal capabilities and its efficacy in biofilm eradication. Combining photothermal activity, targeted NO release and antifouling surface, this multifaceted wound dressing addresses key challenges in bacterial infection management and biofilm eradication, promoting efficient wound healing.

Oxidative Stress Biomarkers in Male Infertility: Established Methodologies and Future Perspectives

Male fertility can be affected by oxidative stress (OS), which occurs when an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralize them arises. OS can damage cells and influence sperm production. High levels of lipid peroxidation have been linked to reduced sperm motility and decreased fertilization ability. This literature review discusses the most commonly used biomarkers to measure sperm damage caused by ROS, such as the high level of OS in seminal plasma as an indicator of imbalance in antioxidant activity. The investigated biomarkers include 8-hydroxy-2-deoxyguanosine acid (8-OHdG), a marker of DNA damage caused by ROS, and F2 isoprostanoids (8-isoprostanes) produced by lipid peroxidation. Furthermore, this review focuses on recent methodologies including the NGS polymorphisms and differentially expressed gene (DEG) analysis, as well as the epigenetic mechanisms linked to ROS during spermatogenesis along with new methodologies developed to evaluate OS biomarkers. Finally, this review addresses a valuable insight into the mechanisms of male infertility provided by these advances and how they have led to new treatment possibilities. Overall, the use of biomarkers to evaluate OS in male infertility has supplied innovative diagnostic and therapeutic approaches, enhancing our understanding of male infertility mechanisms.

Ciprofloxacin-Loaded, pH-Responsive PAMAM-Megamers Functionalized with S-Nitrosylated Hyaluronic Acid Support Infected Wound Healing in Mice without Inducing Antibiotic Resistance

Antimicrobial-resistant bacterial infections threaten to become the number one cause of death by the year 2050. Since the speed at which antimicrobial-resistance develops is exceeding the pace at which new antimicrobials come to the market, this threat cannot be countered by making more, new and stronger antimicrobials. Promising new antimicrobials should not only kill antimicrobial-resistant bacteria, but also prevent development of new bacterial resistance mechanisms in strains still susceptible. Here, PAMAM-dendrimers are clustered using glutaraldehyde to form megamers that are core-loaded with ciprofloxacin and functionalized with HA-SNO. Megamers are enzymatically disintegrated in an acidic pH, as in infectious biofilms, yielding release of ciprofloxacin and NO-generation by HA-SNO. NO-generation does not contribute to the killing of planktonic Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa, but in a biofilm-mode of growth short-lived NO-assisted killing of both ciprofloxacin-susceptible and ciprofloxacin-resistant bacterial strains by the ciprofloxacin released. Repeated sub-culturing of ciprofloxacin-susceptible bacteria in presence of ciprofloxacin-loaded and HA-SNO functionalized PAMAM-megamers does not result in ciprofloxacin-resistant variants as does repeated culturing in presence of ciprofloxacin. Healing of wounds infected by a ciprofloxacin-resistant S. aureus variant treated with ciprofloxacin-loaded, HA-SNO functionalized megamers proceed faster through NO-assisted ciprofloxacin killing of infecting bacteria and stimulation of angiogenesis.

Spin-orbit charge transfer from guanine and 9-methylguanine radical cations to nitric oxide radicals and the induced triplet-to-singlet intersystem crossing

Nitric oxide (●NO) participates in many biological activities, including enhancing DNA radiosensitivity in ionizing radiation-based radiotherapy. To help understand the radiosensitization of ●NO, we report reaction dynamics between ●NO and the radical cations of guanine (a 9HG●+ conformer) and 9-methylguanine (9MG●+). On the basis of the formation of 9HG●+ and 9MG●+ in the gas phase and the collisions of the radical cations with ●NO in a guided-ion beam mass spectrometer, the charge transfer reactions of 9HG●+ and 9MG●+ with ●NO were examined. For both reactions, the kinetic energy-dependent product ion cross sections revealed a threshold energy that is 0.24 (or 0.37) eV above the 0 K product 9HG (or 9MG) + NO+ asymptote. To interrogate this abnormal threshold behavior, the reaction potential energy surface for [9MG + NO]+ was mapped out at closed-shell singlet, open-shell singlet, and triplet states using density functional and coupled cluster theories. The results showed that the charge transfer reaction requires the interaction of a triplet-state surface originating from a reactant-like precursor complex 3[9MG●+(↑)⋅(↑)●NO] with a closed-shell singlet-state surface evolving from a charge-transferred complex 1[9MG⋅NO+]. During the reaction, an electron is transferred from π∗(NO) to perpendicular π∗(9MG), which introduces a change in orbital angular momentum. The latter offsets the change in electron spin angular momentum and facilitates intersystem crossing. The reaction threshold in excess of the 0 K thermochemistry and the low charge-transfer efficiency are rationalized by the vibrational excitation in the product ion NO+ and the kinetic shift arising from a long-lived triplet intermediate.

Enhanced Bacterial-Infected Wound Healing by Nitric Oxide-Releasing Topological Supramolecular Nanocarriers with Self-Optimized Cooperative Multi-Point Anchoring

Polymeric systems that provide cationic charges or biocide-release therapeutics are used to treat the bacteria-infected wound. However, most antibacterial polymers based on topologies with restricted molecular dynamics still do not satisfy the clinical requirements due to their limited antibacterial efficacy at safe concentrations in vivo. Here a NO-releasing topological supramolecular nanocarrier with rotatable and slidable molecular entities is reported to provide conformational freedom to promote the interactions between the carrier and the pathogenic microbes, hence greatly improving the antibacterial performance. With improved contacting-killing and efficient delivery of NO biocide from the molecularly dynamic cationic ligand design, the NO-loaded topological nanocarrier achieves excellent antibacterial and anti-biofilm effects via destroying the bacterial membrane and DNA. MRSA-infected rat model is also brought out to demonstrate its wound-healing effect with neglectable toxicity in vivo. Introducing flexible molecular motions into therapeutic polymeric systems is a general design to enhance the healing of a range of diseases.

Oxidation of Aldehydes Used as Food Additives by Peroxynitrite

Benzaldehyde and its derivatives are used as food supplements. These substances can be used mainly as flavorings or as antioxidants. Besides, peroxynitrite, an oxidizing agent, could be formed in canned food. Both species could react between them. The present article has focused on the kinetic study of the oxidation of aldehydes by peroxynitrite. A reaction mechanism that justifies all the experimental results is proposed. This mechanism, in acidic media, passes through three competitive pathways: (a) a radical attack that produces benzoic acid. (b) peracid oxidation, and (c) a nucleophilic attack of peroxynitrous acid over aldehyde to form an intermediate, X, that produces benzoic acid, or, through a Cannizzaro-type reaction, benzoic acid and benzyl alcohol. All rate constants involved in the third pathway (c) have been calculated. These results have never been described in the literature in acid media. A pH effect was analyzed.

Establishment of a human induced pluripotent stem cell derived alveolar organoid for toxicity assessment

Alveolar epithelial cells (AECs) are vulnerable to injury, which can result in epithelial hyperplasia, apoptosis, and chronic inflammation. In this study, we developed human induced pluripotent stem cell (hiPS) cell-derived AECs (iAECs) and the iAECs based organoids (AOs) for testing AEC toxicity after chemical exposure. HiPS cells were cultured for 14 days with differentiation medium corresponding to each step, and the iAECs-based AOs were maintained for another 14 days. SFTPC and AQP5 were expressed in the AOs, and mRNA levels of SOX9, NKX2.1, GATA6, HOPX, and ID2 were increased. The AOs were exposed for 24 h to nine chemical substances, and IC₅₀ values of the nine chemicals were determined using MTT assay. When the correlations between iAECs 2D culture and AOs 3D culture were calculated using Pearson's correlation coefficient r value, the nine chemicals that caused a significant decrease of cell viability in 3D culture were found to be highly correlated in 2D culture. The cytotoxicity and nitric oxide release in AO cultured with macrophages were then investigated. When AOs with macrophages were exposed to sodium chromate for 24 h, the IC₅₀ value and nitric oxide production were higher than when the AOs were exposed alone. Taken together, the AO-based 3D culture system provides a useful platform for understanding biological characteristics of AECs and modeling chemical exposures.

Identification and verification of ferroptosis-related genes in gastric intestinal metaplasia

Background: Gastric intestinal metaplasia (IM) is the key link of gastric precancerous lesions. Ferroptosis is a novel form of programmed cell death. However, its impact on IM is unclear. The focus of this study is to identify and verify ferroptosis-related genes (FRGs) that may be involved in IM by bioinformatics analysis. Materials and methods: Differentially expressed genes (DEGs) were obtained from microarray dataset GSE60427 and GSE78523 downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed ferroptosis-related genes (DEFRGs) were obtained from overlapping genes of DEGs and FRGs got from FerrDb. DAVID database was used for functional enrichment analysis. Protein-protein interaction (PPI) analysis and Cytoscape software were used to screen hub gene. In addition, we built a receiver operating characteristic (ROC) curve and verified the relative mRNA expression by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Finally, the CIBERSORT algorithm was used to analyze the immune infiltration in IM. Results: First, a total of 17 DEFRGs were identified. Second, a gene module identified by Cytoscape software was considered as hub gene: PTGS2, HMOX1, IFNG, and NOS2. Third, ROC analysis showed that HMOX1 and NOS2 had good diagnostic characteristics. qRT-PCR experiments confirmed the differential expression of HMOX1 in IM and normal gastric tissues. Finally, immunoassay showed that the proportion of T cells regulatory (Tregs) and macrophages M0 in IM was relatively higher, while the proportion of T cells CD4 memory activated and dendritic cells activated was lower. Conclusion: We found significant associations between FRGs and IM, and HMOX1 may be diagnostic biomarkers and therapeutic targets for IM. These results may enhance our understanding of IM and may contribute to its treatment.

Reactive Molecular Dynamics Simulation of the Structural Damages of the B-DNA Induced by the Oxidation/Nitration of Guanine

Reactive molecular dynamics simulations (RMD) have been carried out to investigate structural alterations of the dodecamer double-strand B-DNA due to the oxidation/nitration modifications introduced to its guanine bases, including 8-oxoguanine, 8-nitroguanine, and 5-guanidino-4-nitroimidazole, considering two distribution patterns. These modifications may arise in the case of cancer treatment using oxidative/nitrosative reactive nitrogen species as anticancer agents. Results show that these mutations affect structural characteristics of the B-DNA dodecamer in the order 8-nitroguanine > 5-guanidino-4-nitroimidazole ≫ 8-oxoguanine. For instance, the base-pair per turn for these modified B-DNA are changed respectively to 9.79, 10.88 and 10.58 from 10.51 in the native defect-free B-DNA, which is compatible with the experimental value of 10.10. In addition, these mutations allow more water molecules to diffuse into the dodecamer structure and consequently increase the possibility of the penetration of reactive and nonreactive species toward constituting nucleic base-pairs. The largest variation of the B-DNA structure is observed for the mutated B-DNA with 8-nitroguanine modifications applied to its separated CG base-pairs along the dodecamer chain. The structural changes introduced by these nitro-/oxo-modified guanine bases can be considered as a critical step in the damage of the DNA structure and alterations of its function.

S-nitrosylated PARIS Leads to the Sequestration of PGC-1α into Insoluble Deposits in Parkinson's Disease Model

Neuronal accumulation of parkin-interacting substrate (PARIS), a transcriptional repressor of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), has been observed in Parkinson's disease (PD). Herein, we showed that PARIS can be S-nitrosylated at cysteine 265 (C265), and S-nitrosylated PARIS (SNO-PARIS) translocates to the insoluble fraction, leading to the sequestration of PGC-1α into insoluble deposits. The mislocalization of PGC-1α in the insoluble fraction was observed in S-nitrosocysteine-treated PARIS knockout (KO) cells overexpressing PARIS WT but not S-nitrosylation deficient C265S mutant, indicating that insolubility of PGC-1α is SNO-PARIS-dependent. In the sporadic PD model, α-synuclein preformed fibrils (α-syn PFFs)-injected mice, we found an increase in PARIS, SNO-PARIS, and insoluble sequestration of PGC-1α in substantia nigra (SN), resulting in the reduction of mitochondrial DNA copy number and ATP concentration that were restored by N(ω)-nitro-L-arginine methyl ester, a nitric oxide synthase (NOS) inhibitor. To assess the dopaminergic (DA) neuronal toxicity by SNO-PARIS, lentiviral PARIS WT, C265S, and S-nitrosylation mimic C265W was injected into the SN of either PBS- or α-syn PFFs-injected mice. PARIS WT and C265S caused DA neuronal death to a comparable extent, whereas C265W caused more severe DA neuronal loss in PBS-injected mice. Interestingly, there was synergistic DA loss in both lenti-PARIS WT and α-syn PFFs-injected mice, indicating that SNO-PARIS by α-syn PFFs contributes to the DA toxicity in vivo. Moreover, α-syn PFFs-mediated increment of PARIS, SNO-PARIS, DA toxicity, and behavioral deficits were completely nullified in neuronal NOS KO mice, suggesting that modulation of NO can be a therapeutic for α-syn PFFs-mediated neurodegeneration.

NOS2 and S-nitrosothiol signaling induces DNA hypomethylation and LINE-1 retrotransposon expression

Inducible nitric oxide synthase (NOS2) produces high local concentrations of nitric oxide (NO), and its expression is associated with inflammation, cellular stress signals, and cellular transformation. Additionally, NOS2 expression results in aggressive cancer cell phenotypes and is correlated with poor outcomes in patients with breast cancer. DNA hypomethylation, especially of noncoding repeat elements, is an early event in carcinogenesis and is a common feature of cancer cells. In addition to altered gene expression, DNA hypomethylation results in genomic instability via retrotransposon activation. Here, we show that NOS2 expression and associated NO signaling results in substantial DNA hypomethylation in human cell lines by inducing the degradation of DNA (cytosine-5)–methyltransferase 1 (DNMT1) protein. Similarly, NOS2 expression levels were correlated with decreased DNA methylation in human breast tumors. NOS2 expression and NO signaling also resulted in long interspersed noncoding element 1 (LINE-1) retrotransposon hypomethylation, expression, and DNA damage. DNMT1 degradation was mediated by an NO/p38-MAPK/lysine acetyltransferase 5–dependent mechanism. Furthermore, we show that this mechanism is required for NO-mediated epithelial transformation. Therefore, we conclude that NOS2 and NO signaling results in DNA damage and malignant cellular transformation via an epigenetic mechanism.

Pharmacologic approaches to amino acid depletion for cancer therapy

Cancer cells undergo metabolic reprogramming to support increased demands in bioenergetics and biosynthesis and to maintain reactive oxygen species at optimum levels. As metabolic alterations are broadly observed across many cancer types, metabolic reprogramming is considered a hallmark of cancer. A metabolic alteration commonly seen in cancer cells is an increased demand for certain amino acids. Amino acids are involved in a wide range of cellular functions, including proliferation, redox balance, bioenergetic and biosynthesis support, and homeostatic functions. Thus, targeting amino acid dependency in cancer is an attractive strategy for a number of cancers. In particular, pharmacologically mediated amino acid depletion has been evaluated as a cancer treatment option for several cancers. Amino acids that have been investigated for the feasibility of drug-induced depletion in preclinical and clinical studies for cancer treatment include arginine, asparagine, cysteine, glutamine, lysine, and methionine. In this review, we will summarize the status of current research on pharmacologically mediated amino acid depletion as a strategy for cancer treatment and potential chemotherapeutic combinations that synergize with amino acid depletion to further inhibit tumor growth and progression.

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low / moderate levels may favor tumorigenesis while higher levels would exert anti-tumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "double-edged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression, and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

Obesity, oxidative DNA damage and vitamin D as predictors of genomic instability in children and adolescents

BACKGROUND/OBJECTIVES

Epidemiological evidence indicates obesity in childhood and adolescence to be an independent risk factor for cancer and premature mortality in adulthood. Pathological implications from excess adiposity may begin early in life. Obesity is concurrent with a state of chronic inflammation, a well-known aetiological factor for DNA damage. In addition, obesity has been associated with micro-nutritional deficiencies. Vitamin D has attracted attention for its anti-inflammatory properties and role in genomic integrity and stability. The aim of this study was to determine a novel approach for predicting genomic instability via the combined assessment of adiposity, DNA damage, systemic inflammation, and vitamin D status.

SUBJECTS/METHODS

We carried out a cross-sectional study with 132 participants, aged 10-18, recruited from schools and paediatric obesity clinics in London. Anthropometric assessments included BMI Z-score, waist and hip circumference, and body fat percentage via bioelectrical impedance. Inflammation and vitamin D levels in saliva were assessed by enzyme-linked immunosorbent assay. Oxidative DNA damage was determined via quantification of 8-hydroxy-2'-deoxyguanosine in urine. Exfoliated cells from the oral cavity were scored for genomic instability via the buccal cytome assay.

RESULTS

As expected, comparisons between participants with obesity and normal range BMI showed significant differences in anthropometric measures (p < 0.001). Significant differences were also observed in some measures of genomic instability (p < 0.001). When examining relationships between variables for all participants, markers of adiposity positively correlated with acquired oxidative DNA damage (p < 0.01) and genomic instability (p < 0.001), and negatively correlated with vitamin D (p < 0.01). Multiple regression analyses identified obesity (p < 0.001), vitamin D (p < 0.001), and oxidative DNA damage (p < 0.05) as the three significant predictors of genomic instability.

CONCLUSIONS

Obesity, oxidative DNA damage, and vitamin D deficiency are significant predictors of genomic instability. Non-invasive biomonitoring and predictive modelling of genomic instability in young patients with obesity may contribute to the prioritisation and severity of clinical intervention measures.

The Controversy Persists: Is There a Qualification Criterion to Utilize Inhaled Nitric Oxide in Pre-term Newborns?

Inhaled nitric oxide (iNO) use in premature newborns remains controversial among clinicians. In 2014, the American Academy of Pediatrics, Committee on Fetus and Newborn released a statement that the available data do not support routine iNO use in pre-term newborns. Despite the absence of significant benefits, 2016 California data showed that clinicians continue to utilize iNO in pre-term infants. With studies as recent as January 2017, the Cochrane review confirmed no major advantages of iNO in pre-term newborns. Still, it recognized that a subset of pre-term infants with pulmonary hypertension (PHTN) had not been separately investigated. Furthermore, recent non-randomized controlled trials have suggested that iNO may benefit specific subgroups of pre-term newborns, especially those with PHTN, prolonged rupture of membranes, and antenatal steroid exposure. Those pre-term infants who showed a clinical response to iNO had increased survival without disability. These findings underscore the need for future studies in pre-term newborns with hypoxemic respiratory failure and PHTN. This review will discuss the rationale for using iNO, controversies regarding the diagnosis of PHTN, and additional novel approaches of iNO treatment in perinatal asphyxia and neonatal resuscitation in the pre-term population < 34 weeks gestation.

Integrative Bioinformatics Analysis of iNOS/NOS2 in gastric and colorectal cancer

Objective The aim of the present work was to investigate the expression of nitric oxide synthase 2 (iNOS/ NOS2) in colorectal and gastric cancers and evaluate its association with patient’s prognosis by integrated bioinformatics analysis.

Methods The data for present study was obtained from the TCGA, GTEx, and STRING database. iNOS/NOS2 mRNA expression in normal tissue and colorectal, and gastric cancer tissuea were investigated through the GTEx and TCGA database. iNOS/NOS2 gene mutations and frequency were analyzed in the TCGA database using the cBioPortal online data analysis tool. The protein-protein interaction (PPI) network of iNOS/NOS2 was constructed by STRING database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway of iNOS/NOS2 and relevant proteins involved in the PPI network were enriched and demonstrated by the bubble plot. Comparison of the overall survival(OS) and disease free survival(DFS) between samples expressing high and low levels of iNOS/NOS2 was analysis based on the TCGA databases through the GEPIA online data analysis tool.

Results For colon adenocarcinoma (COAD) and rectal adenocarcinoma(READ) iNOS/NOS2 mRNA expression levels in tumor tissue were significant higher than those of corresponding normal colorectal tissue (p<0.05). iNOS/NOS2 mutations were identified in both colorectal cancer and gastric cancer. Missense substitutions and synonymous substitution were the top two mutation types for colorectal and gastric cancer. The top positive and negative co-expressed genes correlated with iNOS/ NOS2 were TRIM40 (rpearson=0.56, p<0.05) and GDPD5 (rpearson=-0.41, p<0.05) in colorectal cancer respectively andCASP5 (rpearson=0.63,p<0.05) and PIAS3 (rpearson=-0.43,p<0.05) in gastric cancer. Twenty one proteins were included in the PPI network with 51 nodes and 345 edges which indicated the PPI enrichment wassignificant (p=1.0e-16). The KEGG of the included genes were mainly enriched in metabolic pathway and Jak-STAT signaling pathway. There was a significant difference indisease free survival (DFS) between samples expressing high and low iNOS/NOS2 (HR=0.37, p=0.044) in rectal cancer. The difference was not statistical between iNOS/NOS2 high and low expressing groups for overall survival(OS) or DFS in the colon cancer or gastric cancer(p>0.05).

Conclusions iNOS/NOS2 mRNA isup-regulated in tumor tissue compared to corresponding normal tissue in colorectal and gastric cancer which implement it in the development of colorectal and gastric cancers.

Updates on Versatile Role of Putative Gasotransmitter Nitric Oxide: Culprit in Neurodegenerative Disease Pathology

Nitric oxide (NO) is a versatile gasotransmitter that contributes in a range of physiological and pathological mechanims depending on its cellular levels. An appropriate concentration of NO is essentially required for cellular physiology; however, its increased level triggers pathological mechanisms like altered cellular redox regulation, functional impairment of mitochondrion, and modifications in cellular proteins and DNA. Its increased levels also exhibit post-translational modifications in protein through S-nitrosylation of their thiol amino acids, which critically affect the cellular physiology. Along with such modifications, NO could also nitrosylate the endoplasmic reticulum (ER)-membrane located sensors of ER stress, which subsequently affect the cellular protein degradation capacity and lead to aggregation of misfolded/unfolded proteins. Since protein aggregation is one of the pathological hallmarks of neurodegenerative disease, NO should be taken into account during development of disease therapies. In this Review, we shed light on the diverse role of NO in both cellular physiology and pathology and discussed its involvement in various pathological events in the context of neurodegenerative diseases.

Synthesis and in vitro characterization of the genotoxic, mutagenic and cell-transforming potential of nitrosylated heme

Data from epidemiological studies suggest that consumption of red and processed meat is a factor contributing to colorectal carcinogenesis. Red meat contains high amounts of heme, which in turn can be converted to its nitrosylated form, NO-heme, when adding nitrite-containing curing salt to meat. NO-heme might contribute to colorectal cancer formation by causing gene mutations and could thereby be responsible for the association of (processed) red meat consumption with intestinal cancer. Up to now, neither in vitro nor in vivo studies characterizing the mutagenic and cell transforming potential of NO-heme have been published due to the fact that the pure compound is not readily available. Therefore, in the present study, an already existing synthesis protocol was modified to yield, for the first time, purified NO-heme. Thereafter, newly synthesized NO-heme was chemically characterized and used in various in vitro approaches at dietary concentrations to determine whether it can lead to DNA damage and malignant cell transformation. While NO-heme led to a significant dose-dependent increase in the number of DNA strand breaks in the comet assay and was mutagenic in the HPRT assay, this compound tested negative in the Ames test and failed to induce malignant cell transformation in the BALB/c 3T3 cell transformation assay. Interestingly, the non-nitrosylated heme control showed similar effects, but was additionally able to induce malignant transformation in BALB/c 3T3 murine fibroblasts. Taken together, these results suggest that it is the heme molecule rather than the NO moiety which is involved in driving red meat-associated carcinogenesis.

Pseudomonas aeruginosa Biofilm Eradication via Nitric Oxide-Releasing Cyclodextrins

Pseudomonas aeruginosa is the main contributor to the morbidity and mortality of cystic fibrosis (CF) patients. Chronic respiratory infections are rarely eradicated due to protection from CF mucus and the biofilm matrix. The composition of the biofilm matrix determines its viscoelastic properties and affects antibiotic efficacy. Nitric oxide (NO) can both disrupt the physical structure of the biofilm and eradicate interior colonies. The effects of a CF-like growth environment on P. aeruginosa biofilm susceptibility to NO were investigated using parallel plate macrorheology and particle tracking microrheology. Biofilms grown in the presence of mucins and DNA contained greater concentrations of DNA in the matrix and exhibited concomitantly larger viscoelastic moduli compared to those grown in tryptic soy broth. Greater viscoelastic moduli correlated with increased tolerance to tobramycin and colistin. Remarkably, NO-releasing cyclodextrins eradicated all biofilms at the same concentration. The capacity of NO-releasing cyclodextrins to eradicate P. aeruginosa biofilms irrespective of matrix composition suggests that NO-based therapies may be superior antibiofilm treatments compared to conventional antibiotics.

Limiting oxidative DNA damage reduces microbe-induced colitis-associated colorectal cancer

Inflammatory bowel disease patients have a greatly increased risk of developing colitis-associated colon cancer (CAC); however, the basis for inflammation-induced genetic damage requisite for neoplasia is unclear. Using three models of CAC, we find that sustained inflammation triggers 8-oxoguanine DNA lesions. Strikingly, antioxidants or iNOS inhibitors reduce 8-oxoguanine and polyps in CAC models. Because the mismatch repair (MMR) system repairs 8-oxoguanine and is frequently defective in colorectal cancer (CRC), we test whether 8-oxoguanine mediates oncogenesis in a Lynch syndrome (MMR-deficient) model. We show that microbiota generates an accumulation of 8-oxoguanine lesions in MMR-deficient colons. Accordingly, we find that 8-oxoguanine is elevated in neoplastic tissue of Lynch syndrome patients compared to matched untransformed tissue or non-Lynch syndrome neoplastic tissue. While antioxidants reduce 8-oxoguanine, they do not reduce CRC in Lynch syndrome models. Hence, microbe-induced oxidative/nitrosative DNA damage play causative roles in inflammatory CRC models, but not in Lynch syndrome models.

It is unclear how microbial-induced inflammation promotes neoplastic transformation in colitis-associated cancer (CAC). Here, the authors use models of CAC to show that inflammation induces 8-oxoguanine lesions in DNA, and that antioxidants can reduce these DNA lesions as well as CAC.

Spotlight on ROS and β3-Adrenoreceptors Fighting in Cancer Cells

The role of ROS and RNS is a long-standing debate in cancer. Increasing the concentration of ROS reaching the toxic threshold can be an effective strategy for the reduction of tumor cell viability. On the other hand, cancer cells, by maintaining intracellular ROS concentration at an intermediate level called “mild oxidative stress,” promote the activation of signaling that favors tumor progression by increasing cell viability and dangerous tumor phenotype. Many chemotherapeutic treatments induce cell death by rising intracellular ROS concentration. The persistent drug stimulation leads tumor cells to simulate a process called hormesis by which cancer cells exhibit a biphasic response to exposure to drugs used. After a first strong response to a low dose of chemotherapeutic agent, cancer cells start to decrease the response even if high doses of drugs were used. In this framework, β3-adrenoreceptors (β3-ARs) fit with an emerging antioxidant role in cancer. β3-ARs are involved in tumor proliferation, angiogenesis, metastasis, and immune tolerance. Its inhibition, by the selective β3-ARs antagonist (SR59230A), leads cancer cells to increase ROS concentration thus inducing cell death and to decrease NO levels thus inhibiting angiogenesis. In this review, we report an overview on reactive oxygen biology in cancer cells focusing on β3-ARs as new players in the antioxidant pathway.

Chicken lines divergently selected on feather pecking differ in immune characteristics

It is crucial to identify whether relations between immune characteristics and damaging behaviors in production animals exist, as these behaviors reduce animal welfare and productivity. Feather pecking (FP) is a damaging behavior in chickens, which involves hens pecking and pulling at feathers of conspecifics. To further identify relationships between the immune system and FP we characterized high FP (HFP) and low FP (LFP) selection lines with regard to nitric oxide (NO) production by monocytes, specific antibody (SpAb) titers, natural (auto)antibody (N(A)Ab) titers and immune cell subsets. NO production by monocytes was measured as indicator for innate pro-inflammatory immune functioning, SpAb titers were measured as part of the adaptive immune system and N(A)Ab titers were measured as they play an essential role in both innate and adaptive immunity. Immune cell subsets were measured to identify whether differences in immune characteristics were reflected by differences in the relative abundance of immune cell subsets. Divergent selection on FP affected NO production by monocytes, SpAb and N(A)Ab titers, but did not affect immune cell subsets. The HFP line showed higher NO production by monocytes and higher IgG N(A)Ab titers compared to the LFP line. Furthermore the HFP line tended to have lower IgM NAAb titers, but higher IgM and IgG SpAb titers compared to the LFP line. Thus, divergent selection on FP affects the innate and adaptive immune system, where the HFP line seems to have a more responsive immune system compared to the LFP line. Although causation cannot be established in the present study, it is clear that relationships between the immune system and FP exist. Therefore, it is important to take these relationships into account when selecting on behavioral or immunological traits.

Plasma-sensitive Escherichia coli mutants reveal plasma resistance mechanisms

Non-thermal atmospheric pressure plasmas are investigated as augmenting therapy to combat bacterial infections. The strong antibacterial effects of plasmas are attributed to the complex mixture of reactive species, (V)UV radiation and electric fields. The experience with antibiotics is that upon their introduction as medicines, resistance occurs in pathogens and spreads. To assess the possibility of bacterial resistance developing against plasma, we investigated intrinsic protective mechanisms that allow Escherichia coli to survive plasma stress. We performed a genome-wide screening of single-gene knockout mutants of E. coli and identified 87 mutants that are hypersensitive to the effluent of a microscale atmospheric pressure plasma jet. For selected genes ( cysB, mntH, rep and iscS) we showed in complementation studies that plasma resistance can be restored and increased above wild-type levels upon over-expression. To identify plasma-derived components that the 87 genes confer resistance against, mutants were tested for hypersensitivity against individual stressors (hydrogen peroxide, superoxide, hydroxyl radicals, ozone, HOCl, peroxynitrite, NO•, nitrite, nitrate, HNO3, acid stress, diamide, heat stress and detergents). k-means++ clustering revealed that most genes protect from hydrogen peroxide, superoxide and/or nitric oxide. In conclusion, individual bacterial genes confer resistance against plasma providing insights into the antibacterial mechanisms of plasma.

Photosensitivity of Aqueous Sodium Nitroprusside Solutions: Nitric Oxide Release versus Cyanide Toxicity

Photolysis of the pentacyanonitrosylferrate (II) ion in sodium nitroprusside (SNP) solutions involves a competition between photosubstitution and photo-oxidation reactions, where the nitrosyl and cyanide ligands can be released as free nitric oxide (NO) or NO+ and free CN- or CN radical. We have irradiated aqueous SNP solutions at several narrow wavelength ranges in the UV/Vis region (314–576 nm), with the aim of investigating the photolability of the CN and NO ligands. Kinetics of photolysis were used to characterize the photosensitivity of SNP solutions in the range 314–576 nm. Spectral changes in the UV/Vis and IR regions upon irradiation and assays for the detection of free CN- and NO, provided additional evidences for the absence of photoprocesses leading to the release of CN- with λirr > 480 nm. In this condition, the main photoproducts were found to be the [FeIII(CN)5(H2O)]2- ion and NO, formed in a intramolecular photo-oxidative process. Irradiation with unfiltered UV/Vis light and with λirr < 480 nm, lead to the release of both CN- and NO and to a mixture of ferrocyanide and ferricyanide products. These results confirm that the exposure of SNP solutions to UV/Vis light below λirr = 480 nm can lead to cyanide poisoning and further support that above this wavelength limit, a selective NO release from SNP can be achieved, with possible implications for its biochemical action.

Oxidative Stress and Anti-oxidants in Pre and Post-operative Cases of Breast Carcinoma

Objectives

To investigate the existence of oxidative stress in the sera of patients with breast cancer and its effects on the consequent breast cancer.

Materials and Methods

This study included 50 control volunteers, 50 patients with breast cancer, and 50 patients with post-operative breast cancer. Patients with pre-operative cancer were clinically and histopathologically diagnosed for breast carcinoma with stage 0, not having therapeutic history. The control 50 healthy female volunteers had the same socio-economic status, and no history of any cancer. After obtaining consent, venous blood was collected from the volunteers by vein puncture using a 10 mL sterile disposable syringe and needle. About 8 mL of blood was collected, 4 mL of which was poured into a heparinized bulb and 4 mL was allowed to clot. The levels of MDA, NO, GSH, and activities of RBC-SOD (in RBC lysate), NOS, copper and zinc GPx, and CAT, and vitamins A, C, and E metabolites were measured in the sera of each group.

Results

The activities of RBC-SOD and the levels of MDA, NO, as well as the NOS were significantly higher in the sera of all patients with breast cancer as compared with the controls. However, the levels of GSH and vitamins A, C, and E, as well as the activities of copper and zinc GPx and CAT were decreased in patients with breast cancer when compared with the controls.

Conclusion

The study provides further evidence for the presence of oxidative stress in the serum of patients with breast carcinoma. Patients with higher levels of MDA showed deficiencies of antioxidants and trace elements in the serum. A poor dietary antioxidant status and high oxidant levels are associated with the risk of breast cancer, thus suggesting that patients with breast cancer should take nutritive supplements to balance the antioxidant and oxidant levels for better outcomes.

Dual Role of Nitric Oxide in Regulating the Response of β Cells to DNA Damage

SIGNIFICANCE

Cytokines released in and around pancreatic islets during islet inflammation are believed to contribute to impaired β cell function and β cell death during the development of diabetes. Nitric oxide, produced by β cells in response to cytokine exposure, controls many of the responses of β cells during islet inflammation. Recent Advances: Although nitric oxide has been shown to inhibit insulin secretion and oxidative metabolism and induce DNA damage in β cells, it also activates protective pathways that promote recovery of insulin secretion and oxidative metabolism and repair of damaged DNA. Recent studies have identified a novel role for nitric oxide in selectively regulating the DNA damage response in β cells.

CRITICAL ISSUES

Does nitric oxide mediate cytokine-induced β cell damage, or is nitric oxide produced by β cells in response to cytokines to protect β cells from damage?

FUTURE DIRECTIONS

β cells appear to be the only islet endocrine cell type capable of responding to proinflammatory cytokines with the production of nitric oxide, and these terminally differentiated cells have a limited capacity to regenerate. It is likely that there is a physiological purpose for this response, and understanding this could open new areas of study regarding the loss of functional β cell mass during diabetes development.

DNA damage in obesity: Initiator, promoter and predictor of cancer

Epidemiological evidence linking obesity with increased risk of cancer is steadily growing, although the causative aspects underpinning this association are only partially understood. Obesity leads to a physiological imbalance in the regulation of adipose tissue and its normal functioning, resulting in hyperglycaemia, dyslipidaemia and inflammation. These states promote the generation of oxidative stress, which is exacerbated in obesity by a decline in anti-oxidant defence systems. Oxidative stress can have a marked impact on DNA, producing mutagenic lesions that could prove carcinogenic. Here we review the current evidence for genomic instability, sustained DNA damage and accelerated genome ageing in obesity. We explore the notion of genotoxicity, ensuing from systemic oxidative stress, as a key oncogenic factor in obesity. Finally, we advocate for early, pre-malignant assessment of genome integrity and stability to inform surveillance strategies and interventions.

Protective effect of carnosine and N-acetylcysteine against sodium nitrite-induced oxidative stress and DNA damage in rat intestine

The widespread use of sodium nitrite (NaNO₂) as food preservative, rampant use of nitrogenous fertilizers for agricultural practices, and improper disposal of nitrogenous wastes have drastically increased human exposure to high nitrite levels causing various health disorders and death. In the present study, the protective effect of carnosine and N-acetylcysteine (NAC) against NaNO₂-induced intestinal toxicity in rats was investigated. Animals were given a single acute oral dose of NaNO₂ at 60 mg/kg body weight with or without prior administration of either carnosine at 100 mg/kg body weight/day for 7 days or NAC at 100 mg/kg body weight/day for 5 days. Rats were killed after 24 h, and intestinal preparations were used for the evaluation of biochemical alterations and histological abrasions. Administration of NaNO₂ alone decreased the activities of intestinal brush border membrane and metabolic enzymes and significantly weakened the anti-oxidant defense system. DNA damage was also evident as observed by increased DNA-protein crosslinking and fragmentation. However, prior administration of carnosine or NAC significantly ameliorated NaNO₂-induced damage in intestinal cells. Histological studies support these biochemical results, showing intestinal damage in NaNO₂-treated animals and reduced tissue injury in the combination groups. The intrinsic anti-oxidant properties of carnosine and NAC must have contributed to the observed mitigation of nitrite-induced metabolic alterations and oxidative damage. Based on further validation from clinical trials, carnosine and NAC can potentially be used as chemo-preventive agents against NaNO₂ toxicity.

Host-Derived Nitric Oxide and Its Antibacterial Effects in the Urinary Tract

Urinary tract infection (UTI) is one of the most common bacterial infections in humans, and the majority are caused by uropathogenic Escherichia coli (UPEC). The rising antibiotic resistance among UPEC and the frequent failure of antibiotics to effectively treat recurrent UTI and catheter-associated UTI motivate research on alternative ways of managing UTI. Abundant evidence indicates that the toxic radical nitric oxide (NO), formed by activation of the inducible nitric oxide synthase, plays an important role in host defence to bacterial infections, including UTI. The major source of NO production during UTI is from inflammatory cells, especially neutrophils, and from the uroepithelial cells that are known to orchestrate the innate immune response during UTI. NO and reactive nitrogen species have a wide range of antibacterial targets, including DNA, heme proteins, iron-sulfur clusters, and protein thiol groups. However, UPEC have acquired a variety of defence mechanisms for protection against NO, such as the NO-detoxifying enzyme flavohemoglobin and the NO-tolerant cytochrome bd-I respiratory oxidase. The cytotoxicity of NO-derived intermediates is nonspecific and may be detrimental to host cells, and a balanced NO production is crucial to maintain the tissue integrity of the urinary tract. In this review, we will give an overview of how NO production from host cells in the urinary tract is activated and regulated, the effect of NO on UPEC growth and colonization, and the ability of UPEC to protect themselves against NO. We also discuss the attempts that have been made to develop NO-based therapeutics for UTI treatment.

Nitric oxide induced S-nitrosation causes base excision repair imbalance

It is well established that inflammation leads to the creation of potent DNA damaging chemicals, including reactive oxygen and nitrogen species. Nitric oxide can react with glutathione to create S-nitrosoglutathione (GSNO), which can in turn lead to S-nitrosated proteins. Of particular interest is the impact of GSNO on the function of DNA repair enzymes. The base excision repair (BER) pathway can be initiated by the alkyl-adenine DNA glycosylase (AAG), a monofunctional glycosylase that removes methylated bases. After base removal, an abasic site is formed, which then gets cleaved by AP endonuclease and processed by downstream BER enzymes. Interestingly, using the Fluorescence-based Multiplexed Host Cell Reactivation Assay (FM-HCR), we show that GSNO actually enhances AAG activity, which is consistent with the literature. This raised the possibility that there might be imbalanced BER when cells are challenged with a methylating agent. To further explore this possibility, we confirmed that GSNO can cause AP endonuclease to translocate from the nucleus to the cytoplasm, which might further exacerbate imbalanced BER by increasing the levels of AP sites. Analysis of abasic sites indeed shows GSNO induces an increase in the level of AP sites. Furthermore, analysis of DNA damage using the CometChip (a higher throughput version of the comet assay) shows an increase in the levels of BER intermediates. Finally, we found that GSNO exposure is associated with an increase in methylation-induced cytotoxicity. Taken together, these studies support a model wherein GSNO increases BER initiation while processing of AP sites is decreased, leading to a toxic increase in BER intermediates. This model is also supported by additional studies performed in our laboratory showing that inflammation in vivo leads to increased large-scale sequence rearrangements. Taken together, this work provides new evidence that inflammatory chemicals can drive cytotoxicity and mutagenesis via BER imbalance.

Acute oral dose of sodium nitrite causes redox imbalance and DNA damage in rat kidney

Sodium nitrite (NaNO₂ ) is widely used as a food additive and preservative in fish and meat products. We have evaluated the effect of a single acute oral dose of NaNO₂ on oxidative stress parameters, antioxidant capacity, and DNA in rat kidney. Male Wistar rats were divided into four groups and given single oral dose of NaNO₂ at 20, 40, 60, and 75 mg/kg body weight; untreated rats served as the control group. All animals in NaNO₂ -treated groups showed marked alterations in various parameters of oxidative stress as compared to the control group. This included increase in lipid peroxidation, protein oxidation, hydrogen peroxide levels, and decrease in reduced glutathione content and antioxidant capacity. Administration of NaNO₂ also increased DNA damage as evident from release of free nucleotides and confirmed by comet assay. It also led to greater cross-linking of DNA to proteins. Histological analysis showed marked morphological changes in the kidney of NaNO₂ -treated animals. These alterations could be due to increased free radical generation or direct chemical modification by reaction intermediates. Our results suggest that nitrite-induced nephrotoxicity is mediated through redox imbalance and results in DNA damage.

Mechanistic studies of the antibiofilm activity and synergy with antibiotics of isosorbide mononitrate

The use of nitric oxide (NO), a naturally occurring antimicrobial agent, as an alternative strategy to combat bacterial biofilms has recently gained considerable momentum in light of the global threat of emerging antibiotic resistance. While previous NO-based anti-biofilm approaches were aimed at killing bacterial cells within biofilms, NO has also been recently identified as a key mediator of biofilm dispersal, causing the release of cells from the biofilm community. This is of great interest towards the design of more effective anti-biofilm strategies but further studies are warranted to validate this concept. Therefore, in the present study we investigated whether a NO precursor, isosorbide mononitrate (ISMN) or its analogue D-isosorbide can induce bacteria cell dispersal from Staphylococcus aureus (S. aureus) biofilms and explored the potential synergy of ISMN and the antimicrobial compounds mupirocin and ciprofloxacin in biofilm eradication. This study demonstrate that ISMN causes dispersal of S. aureus biofilm bacteria, particularly when exposed to high levels of drug. ISMN at 60mg/mL increased the number of colony forming units (CFU) (~3log₁₀ and ~5log₁₀) of planktonic bacteria after 6 and 24-h exposure respectively, compared to control biofilms. This suggests that ISMN induces the transition of sessile biofilm cells to free-swimming planktonic cells. In addition, ISMN exhibits synergistic effects against S. aureus biofilms with ciprofloxacin when tested above its minimum inhibitory concentration (MIC). Specifically, exposure to ISMN significantly enhanced the efficacy of ciprofloxacin by reducing the number of CFU (~3log₁₀ or ~2log₁₀) of biofilm-associated and planktonic bacteria respectively, compared to drug alone. Combined exposure to both ISMN and certain antimicrobial agents may therefore offer an innovative approach to control persistent biofilm and biofilm-associated infections.

Inducible Nitric Oxide Synthase in the Carcinogenesis of Gastrointestinal Cancers

SIGNIFICANCE

Gastrointestinal (GI) cancer taken together constitutes one of the most common cancers worldwide with a broad range of etiological mechanisms. In this review, we have examined the impact of nitric oxide (NO) on the etiology of colon, colorectal, gastric, esophageal, and liver cancers. Recent Advances: Despite differences in etiology, initiation, and progression, chronic inflammation has been shown to be a common element within these cancers showing interactions of numerous pathways. NO generated at the inflammatory site contributes to the initiation and progression of disease. The amount of NO generated, time, and site vary and are an important determinant of the biological effects initiated. Among the nitric oxide synthase enzymes, the inducible isoform has the most diverse range, participating in numerous carcinogenic processes. There is emerging evidence showing that inducible nitric oxide synthase (NOS2) plays a central role in the process of tumor initiation and/or development.

CRITICAL ISSUES

Redox inflammation through NOS2 and cyclooxygenase-2 participates in driving the mechanisms of initiation and progression in GI cancers.

FUTURE DIRECTIONS

Understanding the underlying mechanism involved in NOS2 activation can provide new insights into important prevention and treatment strategies. Antioxid. Redox Signal. 26, 1059-1077.

Role of Nitric Oxide-Releasing Chitosan Oligosaccharides on Mucus Viscoelasticity

Nitric oxide (NO)-releasing chitosan oligosaccharides were modified with ester functional groups to examine how the mucoadhesive nature of the scaffold impacts the ability of NO to degrade mucins from human bronchial epithelial cell cultures and clinical sputum samples collected from patients with cystic fibrosis (CF). Agarose gel electrophoresis experiments indicated that the mucoadhesive NO-releasing chitosan oligosaccharides degraded both the purified mucins and sputum, while control scaffolds (without NO release or mucoadhesive ligands) had no effect on mucin structure. Microscopic observations of sputum treated with the mucoadhesive NO-releasing chitosan oligosaccharide confirmed degradation of the mucin and DNA networks. Similarly, the viscosity and elasticity of sputum were reduced upon treatment with the mucoadhesive NO-releasing chitosan, demonstrating the potential utility of these NO-releasing scaffolds as mucolytic agents.

Anti-Inflammatory Activity and Structure-Activity Relationships of Brominated Indoles from a Marine Mollusc

Marine molluscs are rich in biologically active natural products that provide new potential sources of anti-inflammatory agents. Here we used bioassay guided fractionation of extracts from the muricid Dicathais orbita to identify brominated indoles with anti-inflammatory activity, based on the inhibition of nitric oxide (NO) and tumour necrosis factor α (TNFα) in lipopolysaccharide (LPS) stimulated RAW264.7 macrophages and prostaglandin E2 (PGE2) in calcium ionophore-stimulated 3T3 ccl-92 fibroblasts. Muricid brominated indoles were then compared to a range of synthetic indoles to determine structure-activity relationships. Both hypobranchial gland and egg extracts inhibited the production of NO significantly with IC₅₀ of 30.8 and 40 μg/mL, respectively. The hypobranchial gland extract also inhibited the production of TNFα and PGE2 with IC₅₀ of 43.03 µg/mL and 34.24 µg/mL, respectively. The purified mono-brominated indole and isatin compounds showed significant inhibitory activity against NO, TNFα, and PGE2, and were more active than dimer indoles and non-brominated isatin. The position of the bromine atom on the isatin benzene ring significantly affected the activity, with 5Br > 6Br > 7Br. The mode of action for the active hypobranchial gland extract, 6-bromoindole, and 6-bromoisatin was further tested by the assessment of the translocation of nuclear factor kappa B (NFκB) in LPS-stimulated RAW264.7 mouse macrophage. The extract (40 µg/mL) significantly inhibited the translocation of NFκB in the LPS-stimulated RAW264.7 macrophages by 48.2%, whereas 40 µg/mL of 6-bromoindole and 6-bromoistain caused a 60.7% and 63.7% reduction in NFκB, respectively. These results identify simple brominated indoles as useful anti-inflammatory drug leads and support the development of extracts from the Australian muricid D. orbita, as a new potential natural remedy for the treatment of inflammation.

Acute oral dose of sodium nitrite induces redox imbalance, DNA damage, metabolic and histological changes in rat intestine

Industrialization and unchecked use of nitrate/nitrite salts for various purposes has increased human exposure to high levels of sodium nitrite (NaNO₂) which can act as a pro-oxidant and pro-carcinogen. Oral exposure makes the gastrointestinal tract particularly susceptible to nitrite toxicity. In this work, the effect of administration of a single acute oral dose of NaNO₂ on rat intestine was studied. Animals were randomly divided into four groups and given single doses of 20, 40, 60 and 75 mg NaNO₂/kg body weight. Untreated animals served as the control group. An NaNO₂ dose-dependent decline in the activities of brush border membrane enzymes, increase in lipid peroxidation, protein oxidation, hydrogen peroxide levels and decreased thiol content was observed in all treated groups. The activities of various metabolic and antioxidant defense enzymes were also altered. NaNO₂ induced a dose-dependent increase in DNA damage and DNA-protein crosslinking. Histopathological studies showed marked morphological damage in intestinal cells. The intestinal damage might be due to nitrite-induced oxidative stress, direct action of nitrite anion or chemical modification by reaction intermediates.

A type I IFN-dependent DNA damage response regulates the genetic program and inflammasome activation in macrophages

Macrophages produce genotoxic agents, such as reactive oxygen and nitrogen species, that kill invading pathogens. Here we show that these agents activate the DNA damage response (DDR) kinases ATM and DNA-PKcs through the generation of double stranded breaks (DSBs) in murine macrophage genomic DNA. In contrast to other cell types, initiation of this DDR depends on signaling from the type I interferon receptor. Once activated, ATM and DNA-PKcs regulate a genetic program with diverse immune functions and promote inflammasome activation and the production of IL-1β and IL-18. Indeed, following infection with Listeria monocytogenes, DNA-PKcs-deficient murine macrophages produce reduced levels of IL-18 and are unable to optimally stimulate IFN-γ production by NK cells. Thus, genomic DNA DSBs act as signaling intermediates in murine macrophages, regulating innate immune responses through the initiation of a type I IFN-dependent DDR.

DNA double-strand break repair is involved in desiccation resistance of Sinorhizobium meliloti, but is not essential for its symbiotic interaction with Medicago truncatula

The soil bacterium Sinorhizobium meliloti, a nitrogen-fixing symbiont of legume plants, is exposed to numerous stress conditions in nature, some of which cause the formation of harmful DNA double-strand breaks (DSBs). In particular, the reactive oxygen species (ROS) and the reactive nitrogen species (RNS) produced during symbiosis, and the desiccation occurring in dry soils, are conditions which induce DSBs. Two major systems of DSB repair are known in S. meliloti: homologous recombination (HR) and non-homologous end-joining (NHEJ). However, their role in the resistance to ROS, RNS and desiccation has never been examined in this bacterial species, and the importance of DSB repair in the symbiotic interaction has not been properly evaluated. Here, we constructed S. meliloti strains deficient in HR (by deleting the recA gene) or in NHEJ (by deleting the four ku genes) or both. Interestingly, we observed that ku and/or recA genes are involved in S. meliloti resistance to ROS and RNS. Nevertheless, an S. meliloti strain deficient in both HR and NHEJ was not altered in its ability to establish and maintain an efficient nitrogen-fixing symbiosis with Medicago truncatula, showing that rhizobial DSB repair is not essential for this process. This result suggests either that DSB formation in S. meliloti is efficiently prevented during symbiosis or that DSBs are not detrimental for symbiosis efficiency. In contrast, we found for the first time that both recA and ku genes are involved in S. meliloti resistance to desiccation, suggesting that DSB repair could be important for rhizobium persistence in the soil.

Activation of toll-like receptor signaling pathways leading to nitric oxide-mediated antiviral responses

Toll-like receptors (TLRs), well-characterized pattern-recognizing receptors of the innate arm of the immune system, are vital in detecting pathogen-associated molecular patterns (PAMPs). The TLR-PAMP interaction initiates an intracellular signaling cascade, predominantly culminating in upregulation of antiviral components, including inducible nitric oxide synthase (iNOS). After activation, various TLR pathways can promote iNOS production via the myeloid differentiation primary response-88 (MyD-88) adapter protein. Subsequently, iNOS facilitates production of nitric oxide (NO), a highly reactive and potent antiviral molecule that can inhibit replication of RNA and DNA viruses. Furthermore, NO can diffuse freely across cell membranes and elicit antiviral mechanisms in various ways, including direct and indirect damage to viral genomes. This review emphasizes current knowledge of NO-mediated antiviral responses elicited after activation of TLR signaling pathways.

Response to Gaseous NO2 Air Pollutant of P. fluorescens Airborne Strain MFAF76a and Clinical Strain MFN1032

Human exposure to nitrogen dioxide (NO₂), an air pollutant of increasing interest in biology, results in several toxic effects to human health and also to the air microbiota. The aim of this study was to investigate the bacterial response to gaseous NO₂. Two Pseudomonas fluorescens strains, namely the airborne strain MFAF76a and the clinical strain MFN1032 were exposed to 0.1, 5, or 45 ppm concentrations of NO₂, and their effects on bacteria were evaluated in terms of motility, biofilm formation, antibiotic resistance, as well as expression of several chosen target genes. While 0.1 and 5 ppm of NO₂did not lead to any detectable modification in the studied phenotypes of the two bacteria, several alterations were observed when the bacteria were exposed to 45 ppm of gaseous NO₂. We thus chose to focus on this high concentration. NO₂-exposed P. fluorescens strains showed reduced swimming motility, and decreased swarming in case of the strain MFN1032. Biofilm formed by NO₂-treated airborne strain MFAF76a showed increased maximum thickness compared to non-treated cells, while NO₂ had no apparent effect on the clinical MFN1032 biofilm structure. It is well known that biofilm and motility are inversely regulated by intracellular c-di-GMP level. The c-di-GMP level was however not affected in response to NO₂ treatment. Finally, NO₂-exposed P. fluorescens strains were found to be more resistant to ciprofloxacin and chloramphenicol. Accordingly, the resistance nodulation cell division (RND) MexEF-OprN efflux pump encoding genes were highly upregulated in the two P. fluorescens strains. Noticeably, similar phenotypes had been previously observed following a NO treatment. Interestingly, an hmp-homolog gene in P. fluorescens strains MFAF76a and MFN1032 encodes a NO dioxygenase that is involved in NO detoxification into nitrites. Its expression was upregulated in response to NO₂, suggesting a possible common pathway between NO and NO₂ detoxification. Taken together, our study provides evidences for the bacterial response to NO₂ toxicity.

Muscle dysfunction in chronic obstructive pulmonary disease: update on causes and biological findings

Respiratory and/or limb muscle dysfunction, which are frequently observed in chronic obstructive pulmonary disease (COPD) patients, contribute to their disease prognosis irrespective of the lung function. Muscle dysfunction is caused by the interaction of local and systemic factors. The key deleterious etiologic factors are pulmonary hyperinflation for the respiratory muscles and deconditioning secondary to reduced physical activity for limb muscles. Nonetheless, cigarette smoke, systemic inflammation, nutritional abnormalities, exercise, exacerbations, anabolic insufficiency, drugs and comorbidities also seem to play a relevant role. All these factors modify the phenotype of the muscles, through the induction of several biological phenomena in patients with COPD. While respiratory muscles improve their aerobic phenotype (percentage of oxidative fibers, capillarization, mitochondrial density, enzyme activity in the aerobic pathways, etc.), limb muscles exhibit the opposite phenotype. In addition, both muscle groups show oxidative stress, signs of damage and epigenetic changes. However, fiber atrophy, increased number of inflammatory cells, altered regenerative capacity; signs of apoptosis and autophagy, and an imbalance between protein synthesis and breakdown are rather characteristic features of the limb muscles, mostly in patients with reduced body weight. Despite that significant progress has been achieved in the last decades, full elucidation of the specific roles of the target biological mechanisms involved in COPD muscle dysfunction is still required. Such an achievement will be crucial to adequately tackle with this relevant clinical problem of COPD patients in the near-future.

Formation of glutathionyl dinitrosyl iron complexes protects against iron genotoxicity

Dinitrosyl iron(i) complexes (DNICs), intracellular NO donors, are important factors in nitric oxide-dependent regulation of cellular metabolism and signal transduction. It has been shown that NO diminishes the toxicity of iron ions and vice versa. To gain insight into the possible role of DNIC in this phenomenon, we examined the effect of GS-DNIC formation on the ability of iron ions to mediate DNA damage, by treatment of the pUC19 plasmid with physiologically relevant concentrations of GS-DNIC. It was shown that GS-DNIC formation protects against the genotoxic effect of iron ions alone and iron ions in the presence of a naturally abundant antioxidant, GSH. This sheds new light on the iron-related protective effect of NO under the circumstances of oxidative stress.

Near infrared radiation protects against oxygen-glucose deprivation-induced neurotoxicity by down-regulating neuronal nitric oxide synthase (nNOS) activity in vitro

Near infrared radiation (NIR) has been shown to be neuroprotective against neurological diseases including stroke and brain trauma, but the underlying mechanisms remain poorly understood. In the current study we aimed to investigate the hypothesis that NIR may protect neurons by attenuating oxygen-glucose deprivation (OGD)-induced nitric oxide (NO) production and modulating cell survival/death signaling. Primary mouse cortical neurons were subjected to 4 h OGD and NIR was applied at 2 h reoxygenation. OGD significantly increased NO level in primary neurons compared to normal control, which was significantly ameliorated by NIR at 5 and 30 min post-NIR. Neither OGD nor NIR significantly changed neuronal nitric oxide synthase (nNOS) mRNA or total protein levels compared to control groups. However, OGD significantly increased nNOS activity compared to normal control, and this effect was significantly diminished by NIR. Moreover, NIR significantly ameliorated the neuronal death induced by S-Nitroso-N-acetyl-DL-penicillamine (SNAP), a NO donor. Finally, NIR significantly rescued OGD-induced suppression of p-Akt and Bcl-2 expression, and attenuated OGD-induced upregulation of Bax, BAD and caspase-3 activation. These results suggest NIR may protect against OGD at least partially through reducing NO production by down-regulating nNOS activity, and modulating cell survival/death signaling.

Pathogenesis of cholangiocarcinoma: From genetics to signalling pathways

Cholangiocarcinoma (CCA) is a malignant tumour of bile duct epithelial cells with dismal prognosis and rising incidence. Chronic inflammation resulting from liver fluke infection, hepatitis and other inflammatory bowel diseases is a major contributing factor to cholangiocarcinogenesis, likely through accumulation of serial genetic and epigenetic alterations resulting in aberration of oncogenes and tumour suppressors. Recent studies making use of advances in high-throughput genomics have revealed the genetic landscape of CCA, greatly increasing our understanding of its underlying biology. A series of highly recurrent mutations in genes such as TP53, KRAS, SMAD4, BRAF, MLL3, ARID1A, PBRM1 and BAP1, which are known to be involved in cell cycle control, cell signalling pathways and chromatin dynamics, have led to investigations of their roles, through molecular to mouse modelling studies, in cholangiocarcinogenesis. This review focuses on the landscape genetic alterations in CCA and its functional relevance to the formation and progression of CCA.

Pathophysiological Role of Peroxynitrite Induced DNA Damage in Human Diseases: A Special Focus on Poly(ADP-ribose) Polymerase (PARP)

Peroxynitrite is formed in biological systems when nitric oxide and superoxide rapidly interact at near equimolar ratio. Peroxynitrite, though not a free radical by chemical nature, is a powerful oxidant which reacts with proteins, DNA and lipids. These reactions trigger a wide array of cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. The present review outlines the various peroxynitrite-induced DNA modifications with special mention to the formation of 8-nitroguanine and 8-oxoguanine as well as the induction of DNA single strand breakage. Low concentrations of peroxynitrite cause apoptotic death, whereas higher concentrations cause necrosis with cellular energetics (ATP and NAD(+)) serving as control between the two modes of cell death. DNA damage induced by peroxynitrite triggers the activation of DNA repair systems. A DNA nick sensing enzyme, poly(ADP-ribose) polymerase-1 (PARP-1) becomes activated upon detecting DNA breakage and it cleaves NAD(+) into nicotinamide and ADP-ribose and polymerizes the latter on nuclear acceptor proteins. Over-activation of PARP induced by peroxynitrite consumes NAD(+) and consequently ATP decreases, culminating in cell dysfunction, apoptosis or necrosis. This mechanism has been implicated in the pathogenesis of various diseases like diabetes, cardiovascular diseases and neurodegenerative diseases. In this review, we have discussed the cytotoxic effects (apoptosis and necrosis) of peroxynitrite in the etiology of the mentioned diseases, focusing on the role of PARP in DNA repair in presence of peroxynitrite.