8-hydroxyguanine and Pneumonia

Reactive oxygen species inflict oxidative modifications on various biological molecules, including DNA. One of the most abundant DNA base lesions, 8-oxo-7,8-dihydroguanine (8-oxoG) is repaired by 8-oxoguanine DNA glycosylase-1 (OGG1) during DNA base excision repair (OGG1-BER). 8-OxoG accumulation in DNA has been associated with various pathological and aging processes, although its role is unclear. The lack of OGG1-BER in Ogg1(-/-) mice resulted in decreased inflammatory responses and increased susceptibility to infections and metabolic disorders. Therefore, we proposed that OGG1 and/or 8-oxoG base may have a role in immune and homeostatic processes. To test our hypothesis, we challenged mouse lungs with OGG1-BER product 8-oxoG base and changes in gene expression were determined by RNA sequencing and data were analyzed by Gene Ontology and statistical tools. RNA-Seq analysis identified 1592 differentially expressed (≥ 3-fold change) transcripts. The upregulated mRNAs were related to biological processes, including homeostatic, immune-system, macrophage activation, regulation of liquid-surface tension, and response to stimulus. These processes were mediated by chemokines, cytokines, gonadotropin-releasing hormone receptor, integrin, and interleukin signaling pathways. Taken together, these findings point to a new paradigm showing that OGG1-BER plays a role in various biological processes that may benefit the host, but when in excess could be implicated in disease and/or aging processes.

Topics: Administration, Intranasal; Animals; Bronchoalveolar Lavage Fluid; DNA; DNA Glycosylases; DNA Repair; Female; Gene Expression Profiling; Gene Expression Regulation; Guanine; Lung; Metabolic Networks and Pathways; Mice; Mice, Inbred BALB C; Molecular Sequence Annotation; Oxidative Stress; Pneumonia; Reactive Oxygen Species; Signal Transduction; Transcriptome

Allergic airway inflammation is characterized by increased expression of pro-inflammatory mediators, inflammatory cell infiltration, mucus hypersecretion, and airway hyperresponsiveness, in parallel with oxidative DNA base and strand damage, whose etiological role is not understood. Our goal was to establish the role of 8-oxoguanine (8-oxoG), a common oxidatively damaged base, and its repair by 8-oxoguanine DNA glycosylase 1 (Ogg1) in allergic airway inflammatory processes. Airway inflammation was induced by intranasally administered ragweed (Ambrosia artemisiifolia) pollen grain extract (RWPE) in sensitized BALB/c mice. We utilized siRNA technology to deplete Ogg1 from airway epithelium; 8-oxoG and DNA strand break levels were quantified by Comet assays. Inflammatory cell infiltration and epithelial methaplasia were determined histologically, mucus and cytokines levels biochemically and enhanced pause was used as the main index of airway hyperresponsiveness. Decreased Ogg1 expression and thereby 8-oxoG repair in the airway epithelium conveyed a lower inflammatory response after RWPE challenge of sensitized mice, as determined by expression of Th2 cytokines, eosinophilia, epithelial methaplasia, and airway hyperresponsiveness. In contrast, 8-oxoG repair in Ogg1-proficient airway epithelium was coupled to an increase in DNA single-strand break (SSB) levels and exacerbation of allergen challenge-dependent inflammation. Decreased expression of the Nei-like glycosylases Neil1 and Neil2 that preferentially excise ring-opened purines and 5-hydroxyuracil, respectively, did not alter the above parameters of allergic immune responses to RWPE. These results show that DNA SSBs formed during Ogg1-mediated repair of 8-oxoG augment antigen-driven allergic immune responses. A transient modulation of OGG1 expression/activity in airway epithelial cells could have clinical benefits.

Topics: Ambrosia; Animals; Cell Line; DNA; DNA Breaks, Single-Stranded; DNA Glycosylases; DNA Repair; Down-Regulation; Guanine; Lung; Mice; Mice, Inbred C57BL; Pneumonia; Pollen; Respiratory Hypersensitivity; Respiratory Mucosa; RNA, Small Interfering

The two poorly soluble iron containing solid aerosols of siderite (FeCO₃) and magnetite (Fe₃O₄) were compared in a 4-week inhalation study on rats at similar particle mass concentrations of approximately 30 or 100 mg/m³. The particle size distributions were essentially identical (MMAD ≈1.4 μm). The iron-based concentrations were 12 or 38 and 22 or 66 mg Fe/m³ for FeCO₃ and Fe₃O₄, respectively. Modeled and empirically determined iron lung burdens were compared with endpoints suggestive of pulmonary inflammation by determinations in bronchoalveolar lavage (BAL) and oxidative stress in lung tissue during a postexposure period of 3 months. The objective of study was to identify the most germane exposure metrics, that are the concentration of elemental iron (mg Fe/m³), total particle mass (mg PM/m³) or particle volume (μl PM/m³) and their associations with the effects observed. From this analysis it was apparent that the intensity of pulmonary inflammation was clearly dependent on the concentration of particle-mass or -volume and not of iron. Despite its lower iron content, the exposure to FeCO₃ caused a more pronounced and sustained inflammation as compared to Fe₃O₄. Similarly, borderline evidence of increased oxidative stress and inflammation occurred especially following exposure to FeCO₃ at moderate lung overload levels. The in situ analysis of 8-oxoguanine in epithelial cells of alveolar and bronchiolar regions supports the conclusion that both FeCO₃ and Fe₃O₄ particles are effectively endocytosed by macrophages as opposed to epithelial cells. Evidence of intracellular or nuclear sources of redox-active iron did not exist. In summary, this mechanistic study supports previous conclusions, namely that the repeated inhalation exposure of rats to highly respirable pigment-type iron oxides cause nonspecific pulmonary inflammation which shows a clear dependence on the particle volume-dependent lung overload rather than any increased dissolution and/or bioavailability of redox-active iron.

Topics: Animals; Bronchoalveolar Lavage; Carbonates; Epithelial Cells; Ferric Compounds; Ferritins; Ferrosoferric Oxide; Guanine; Heme Oxygenase-1; Iron; Lipid Peroxidation; Lymph Nodes; Male; Neutrophils; Pneumonia; Rats; Rats, Wistar; Solubility; Thiobarbituric Acid Reactive Substances

TiO(2) is considered to be toxicologically inert, at least under nonoverload conditions. To study if there are differences in lung effects of surface treated or untreated TiO(2) we investigated the inflammatory and genotoxic lung effects of two types of commercially available TiO(2) at low doses relevant to the working environment. Rats were exposed by instillation to a single dose of 0.15, 0.3, 0.6, and 1.2 mg of TiO(2) P25 (untreated, hydrophilic surface) or TiO(2) T805 (silanized, hydrophobic surface) particles, suspended in 0.2 ml of physiological saline supplemented with 0.25% lecithin. As control, animals were instilled with the vehicle medium only or with a single dose of 0.6 mg quartz DQ12. At days 3, 21, and 90 after instillation bronchoalveolar lavage was performed and inflammatory signs such as cells, protein, tumor necrosis factor-alpha, fibronectin, and surfactant phospholipids were determined. Additionally, 8 microm frozen sections of the left lobe of the lung were cut and stored at -80 degrees C. The sections were used for immunohistochemical detection of 8-oxoguanine (8-oxoGua) by a polyclonal antibody in the DNA of individual lung cells. In the quartz-exposed animals a strong progression in the lung inflammatory response was observed. Ninety days after exposure a significant increase in the amount of 8-oxoGua in DNA of lung cells was detected. In contrast, animals exposed to TiO(2) P25 or TiO(2) T805 showed no signs of inflammation. The amount of 8-oxoGua as a marker of DNA damage was at the level of control. The results indicate that both types of TiO(2) are inert at applicated doses.

Topics: Air Pollutants, Occupational; Animals; Bronchoalveolar Lavage; Bronchoalveolar Lavage Fluid; Cell Count; Cell Division; DNA Damage; Dose-Response Relationship, Drug; Female; Guanine; Instillation, Drug; Lung; Mutagens; Particle Size; Pneumonia; Pulmonary Surfactants; Quartz; Rats; Rats, Wistar; Surface Properties; Titanium

Exposure to quartz and high concentrations of other poorly soluble particles can lead to the development of lung tumors in the rat. The mechanisms involved in particle-induced carcinogenesis seem to include inflammation-associated production of reactive oxygen species (ROS) and DNA damage. ROS induce 8-oxoguanine (8-oxoGua) and a panel of other oxidation products in DNA. In proliferating cells such DNA lesions can lead to various types of mutations, which might be critical for cancer-related genes with respect to tumor formation. Quartz is known to mediate the induction of 8-oxoGua in the nuclear DNA of lung cells when applied to the lung of rats. We have investigated the time- and dose-dependent biologic effects of quartz and, as a control, corundum, on cell proliferation and various pulmonary inflammation and toxicity markers in rat bronchoalveolar lavage fluid (BALF); on the induction of 8-oxoGua in the DNA of rat lung cells; and on the cellular levels of p53 wild-type and p53 mutant (mut) protein. Rats were exposed by intratracheal instillation to various amounts of quartz (0.3, 1.5, or 7.5 mg/rat) or corundum (0.3, 1.5, or 7.5 mg/rat) and measured at Days 7, 21, and 90 after exposure. Corundum had no adverse effects except a slight elevation of 8-oxoGua at a dose of 7.5 mg/rat. However, significant changes in the BALF were detected at all quartz doses. 8-oxoGua was significantly increased only at 1.5 and 7.5 mg quartz/rat. The amount of cells with detectable p53 wild-type protein levels was increased at 1.5 and 7.5 mg quartz/rat at 7 and 21 d. Elevated amounts of cells with enhanced p53 mut protein levels were measured at all time points after instillation of 7.5 mg quartz/rat.

Topics: Aluminum Oxide; Animals; Bronchoalveolar Lavage Fluid; Cell Division; DNA Damage; Dose-Response Relationship, Drug; Female; Guanine; Immunohistochemistry; Ki-67 Antigen; Lung; Mutagens; Neutrophils; Oxidative Stress; Pneumonia; Proteins; Quartz; Rats; Rats, Wistar; Tumor Suppressor Protein p53